Grimm v. State

Watts, J. It is undisputed that the ultimate question of probable cause to conduct a warrantless search is reviewed by an appellate court de novo ; i.e. , the standard of review for the issue of probable cause is de novo , or without deference. "In reviewing a trial court's ruling on a motion to suppress, an appellate court reviews for clear error the trial court's findings of fact, and reviews without deference the trial court's application of the law to its findings of fact." Varriale v. State , 444 Md. 400 , 410, 119 A.3d 824 , 830 (2015) (citation omitted). It may be less clear, however, whether a particular determination by a trial court is a finding of fact, and thus subject to deference, or a conclusion of law, and thus subject to no deference. See Miller v. Fenton , 474 U.S. 104 , 113, 106 S.Ct. 445 , 88 L.Ed.2d 405 (1985) ("[T]he appropriate methodology for distinguishing questions of fact from questions of law has been, to say the least, elusive." (Citations omitted) ).

This case requires us to determine whether, in the context of a probable cause determination, the issue of a drug detection dog's reliability is a factual question to be reviewed for clear error, or a legal one to be reviewed de novo. This is a matter of first impression, and our resolution of the issue will govern the standard of review of a trial court's determination as to whether a drug detection dog is, or is not, reliable. We set the stage. In this case, Sergeant Christopher Lamb of the Maryland Transportation Authority Police initiated a traffic stop of a vehicle that Brian Grimm, Petitioner, had been driving.

Officer Carl Keightley of the Maryland Transportation Authority Police, a K-9 handler, and Ace, his Belgian Malinois K-9 partner, arrived at the scene of the traffic stop. 1 Ace scanned the vehicle and alerted to it. Sergeant Lamb searched the vehicle and found drugs inside. In the Circuit Court for Anne Arundel County, the State, Respondent, charged Grimm with various drug-related crimes. Grimm moved to suppress the drugs, alleging that Sergeant Lamb lacked probable cause to search his vehicle.

At a hearing on the motion to suppress, the circuit court admitted into evidence several documents, including Ace's training records, Ace's field reports, 2 and Officer Keightley's and Ace's certifications. The State called two expert witnesses: Officer Keightley and Sergeant Mary Davis, the Montgomery County Police Department's K-9 Unit's head trainer. Grimm also called two expert witnesses: Ted Cox, the former head trainer of the Baltimore Police Department's K-9 Unit and the Maryland Transportation Authority Police's K-9 Unit, 3 and Officer Michael McNerney, a trainer of the Maryland Transportation Authority Police's K-9 Unit. Sergeant Davis essentially testified that Ace was reliable, while Cox and Officer McNerney opined that Ace was unreliable.

The circuit court denied the motion to suppress, concluding that Sergeant Lamb had probable cause to search the vehicle. The circuit court found that Sergeant Davis was "the most credible witness[,]" and "accept[ed]" her opinion as to Ace's reliability. Before us, as to the standard of review, Grimm contends that we must review without deference, as opposed to for clear error, the circuit court's determination that Ace was reliable. As to the merits, Grimm argues that, no matter which standard of review applies, the circuit court erred in determining that probable cause existed.

The State responds that the standard of review is for clear error, and asserts that the circuit court did not clearly err in determining that Ace was reliable. Alternatively, the State maintains that, even if probable cause did not exist, the "good faith" exception to the exclusionary rule applies. In Part I below, we conclude that the ultimate question of probable cause to conduct a warrantless search of a vehicle based on a drug detection dog's alert is reviewed de novo ; i.e. , the standard of review as to the issue of probable cause to search based on a drug detection dog's alert is de novo. A determination of probable cause involves a two-step process.

First, a court must identify all of the relevant historical facts that were known to the officer at the time of the search and, if necessary, any relevant or disputed background facts. Second, the court must determine whether those facts give rise to probable cause to search. We conclude that the issue of a drug detection dog's reliability is a factual question. Accordingly, an appellate court reviews for clear error a trial court's determination as to whether a drug detection dog is, or is not, reliable.

In Miller , 474 U.S. at 114 , 106 S.Ct. 445 , the Supreme Court concluded that, where an issue falls somewhere between a clear legal issue and a simple historical fact, the determination of the nature of the issue turns on an analysis of which judicial actor is better positioned to decide the question. As explained below, the issue of a drug detection dog's reliability is, in our view, a background fact that falls somewhere between a clear legal issue and a simple fact. A trial court is better positioned than an appellate court to determine the issue. An issue as to a drug detection dog's reliability requires a trial court to assess the credibility of lay and expert witnesses; to watch, when available, a recording of a drug detection dog's scan; to weigh and determine the weight to be given documentary evidence, such as the drug detection dog's training records, field reports, and certifications; to consider the qualifications of any experts, and their opinions about the evidence; and to determine whether, under the totality of the circumstances, the drug detection dog is reliable; and whether the drug detection dog's alert indicated that drugs were present.

As such, a trial court is better positioned than an appellate court to determine a drug detection dog's reliability. In Part II below, we hold that the circuit court did not clearly err in determining that Ace was reliable, as an abundance of evidence supports the circuit court's finding that Ace was reliable. We conclude that, under the totality of the circumstances, Sergeant Lamb had probable cause for the search, and we do not address the State's argument as to good faith. BACKGROUND Charges and Motion to Suppress On April 19, 2014, in the circuit court, the State charged Grimm with possession of heroin with intent to distribute and other drug-related crimes.

On May 23, 2014, Grimm filed a motion to suppress drugs that had been found in a vehicle that he had been driving. On multiple days, December 17, 2014, January 5 and 13, 2015, and March 17, 2015, the circuit court conducted a hearing on the motion to suppress. Sergeant Lamb's Testimony Regarding the Traffic Stop At the hearing, as a witness for the State, Sergeant Lamb testified that, on April 18, 2014, a detective with the High Intensity Drug Trafficking Area team provided him with a description of a man who was suspected to be driving north on Interstate 95 from Atlanta, Georgia to the Baltimore area with a large quantity of controlled dangerous substances. On April 19, 2014, Sergeant Lamb was informed that the man was driving a maroon Honda that was registered in Georgia, that there were multiple occupants in the Honda, and that the man was expected to drive from Maryland Route 100 onto the northbound side of Maryland Route 295.

That same day, Sergeant Lamb saw the Honda travel from Maryland Route 100 onto Maryland Route 295, and saw that, including the driver, the Honda had three occupants who were not wearing seat belts. Sergeant Lamb initiated a traffic stop. Sergeant Lamb testified that Grimm was in the Honda's driver's seat. According to Sergeant Lamb, Grimm's "clothing looked disheveled," and "[h]is hair looked unkempt[,]" which indicated to Sergeant Lamb that "he had been driving for a long time ... and had[ not] been staying anywhere." Sergeant Lamb spoke with Grimm, who "was kind of mumbling" and "rambling a little bit." Grimm did not make eye contact when he was addressing Sergeant Lamb.

Grimm, however, appeared to be "very calm." Grimm provided Sergeant Lamb with his Maryland driver's license and the Honda's registration. Two days earlier, the Honda had been registered in Georgia to a man named Johnny Lee Oglesbee, Jr. Grimm told Sergeant Lamb that he had bought the Honda, but could not afford to register the Honda in his name. Grimm did not say who Oglesbee was. Grimm told Sergeant Lamb that he and three other people had traveled from Baltimore to Atlanta for approximately one week to visit friends and buy the Honda.

Grimm said that he had paid for plane tickets from Baltimore to Atlanta for all four of them. A woman named Davita Henry was in the front passenger seat. A man named Aaron Chase was in the backseat, 4 directly behind Grimm. During the traffic stop, Henry stared straight ahead, and never turned to look at Sergeant Lamb, who was standing on the Honda's passenger side while speaking to Grimm.

Meanwhile, Chase, who "was leaning forward to engage [Sergeant Lamb] in conversation" while he was speaking to Grimm, "was very open with the fact that he was[ ]" not wearing a seat belt, and was "overly polite[.]" Sergeant Lamb explained that people who are "overly polite" may be trying to distract law enforcement officers from "what[ is] going on[.]" Grimm told Sergeant Lamb that there had been a fourth occupant in the Honda, who had been dropped off at an Element Hotel. Grimm told Sergeant Lamb that the fourth occupant and Henry were women whom he knew from a dance club, and that Chase was his friend. At some point, Sergeant Lamb asked Grimm to exit the Honda and walk to the rear of the Honda. Grimm did so.

And, after speaking to Sergeant Lamb, Grimm returned to the driver's seat. Grimm did not fully close the driver's door, and kept his left foot on the asphalt. Grimm also placed a pillow on the door's "windowsill[,]" then laid his head on the pillow. Sergeant Lamb became concerned that Grimm would try to run away.

Sergeant Lamb suspected that criminal activity was afoot, in light of the information he had received from Grimm that four individuals had flown from Baltimore to Atlanta to buy the Honda, and Grimm had paid for the airline tickets, yet, Grimm allegedly was not able to afford to register the Honda in his name, and the circumstance that Chase was overly polite while Henry stared straight ahead. Sergeant Lamb observed that the Honda was a dented, older model, two-door Accord with high mileage and faded paint. Sergeant Lamb testified that both Baltimore and Atlanta are "source cities for" controlled dangerous substances. Sergeant Lamb used his radio to obtain information about Grimm's Maryland driver's license and the Honda's registration, and he learned that both were valid.

Based on his observations, Sergeant Lamb requested a K-9. While Sergeant Lamb was writing warnings for the failure to wear seat belts, Officer Keightley of the K-9 Unit arrived with Ace, a drug detection dog. Sergeant Lamb informed Officer Keightley of what he had observed, and requested a dog scan of the Honda. Officer Keightley told Sergeant Lamb that he wanted the Honda's occupants to exit the Honda before the dog scan occurred.

After the Honda's occupants exited the Honda, Officer Keightley and Ace performed a dog scan, and Officer Keightley advised that Ace had alerted. Sergeant Lamb searched the Honda, and found a large amount of heroin and amphetamine in the "right rear panel[,]" which he described as the "plastic and vinyl armrest and side rail" behind the passenger's door. Testimony of Officer Keightley, Ace's Handler and One of the State's Experts As a witness for the State, Officer Keightley of the Maryland Transportation Authority Police testified that he had been a member of the K-9 Unit since February 2012. In April 2012, Officer Keightley started working with Ace.

Officer Keightley testified about Ace's training and certification. For three months, from April 2012 to July 2012, Cox and Officers McNerney and McCarty provided Ace's initial training. During Ace's initial training, he was trained to recognize the odors of five drugs: marijuana, cocaine, heroin, methamphetamine, and methylenedioxy-methamphetamine. 5 After Ace's initial training, he was trained once a week, for an average of seven hours a week, using "narcotic aids"- i.e. , substances that the crime laboratory had tested and determined to be drugs. The training is designed to mimic events that occur in the field.

During Ace's training, usually, a trainer would set one or multiple narcotic aids in a given area, such as a vehicle or a building; the narcotic aids would sit for twenty to thirty minutes; and then, Officer Keightley and Ace would search the area. Ace's training was documented with a training record that listed dates, times, the narcotic aids that were used, the weights thereof (ranging from a gram to ten pounds), where they were hidden, and whether Ace found them. The Maryland Transportation Authority Police certifies dogs and their handlers every six months. Like other drug detection dogs, to become certified, Ace was tested in "two or three" capacities from among "various areas[,]" including a building, a vehicle, luggage, and an outdoor area.

Officer Keightley and Ace were first certified on July 6, 2012. Officer Keightley and Ace had been certified five times, and were certified as of April 19, 2014. At that time, Officer Keightley and Ace had most recently been certified on January 22, 2014. As of the date of the hearing, Ace had performed dog scans during approximately 100 traffic stops.

The circuit court admitted Officer Keightley as an expert in the field of "K-9 police dog[s] and the detection of controlled dangerous substances"-specifically, marijuana, cocaine, heroin, methamphetamine, and methylenedioxy-methamphetamine. Without objection, the circuit court admitted into evidence: Ace's training records from April 2012 through April 2014; Ace's field reports-which Officer Keightley completed every time that he utilized Ace-from when Officer Keightley and Ace were first certified on July 6, 2012 until April 19, 2014; the Maryland Transportation Authority Police Narcotic/Explosive K-9 Certification Guidelines; and the Maryland Transportation Authority Police K-9 Standard Operating Procedures, which included guidelines for training dogs and handling explosive aids and narcotic aids. The circuit court also admitted into evidence: Officer Keightley's and Ace's July 6, 2012 certification, which was accompanied by score sheets that showed which narcotic aids were used, where they were hidden, and whether Ace found them; Officer Keightley's and Ace's December 10 and 14, 2012 certification, and Officer Keightley's and Ace's July 1, 2013 certification. The second-to-last certification was associated with two dates because, on December 10, 2012, Officer Keightley and Ace passed a test that involved a dog scan of a vehicle, but did not pass a test that involved a dog scan in a building; on December 14, 2012, Officer Keightley and Ace re-took, and passed, the test that involved a dog scan in a building, and Officer McNerney recertified Officer Keightley and Ace.

According to Ace's field reports, between July 6, 2012 and April 19, 2014, Ace had alerted to a vehicle on 51 occasions. Of those 51 occasions, no drugs were found in the vehicle on 19 occasions. Officer Keightley testified that a "non-productive response" occurs when a drug detection dog alerts to a vehicle or building, and an officer searches the vehicle or building, but does not find any contraband. 6 Officer Keightley explained that Ace might alert where drugs used to be, but are no longer, inside a vehicle. Indeed, with regard to 10 of the 19 non-productive responses to vehicles, during interviews, at least one of the vehicle's occupants admitted that drugs had recently been in the vehicle.

Thus, Ace had only 9 non-productive responses where there was no discovery of drugs, and no admission that drugs had recently been in the vehicle. In response to Ace's non-productive responses, Officer Keightley extended Ace's searching time during training. Between January 22, 2014-Officer Keightley's and Ace's most recent certification before the time of the traffic stop on April 19, 2014-and April 19, 2014, Officer Keightley did not receive any warnings that he was doing anything inappropriate. Officer Keightley testified that, on April 19, 2014, he responded to a traffic stop that Sergeant Lamb had initiated.

At the scene, Officer Keightley was asked to conduct a dog scan of the Honda with his K-9, Ace. At the time, both of the Honda's windows were rolled down. Officer Keightley brought Ace to the front of the Honda. On the way to the front of the Honda, Officer Keightley and Ace passed the passenger's door, where Sergeant Lamb ultimately found drugs.

Officer Keightley did not notice any reaction by Ace while they passed the passenger's door. At that time, Officer Keightley had not yet commanded Ace to search. Once in front of the Honda, Officer Keightley told Ace to "foot"- i.e. , to sit next to him. When Ace was quiet, Officer Keightley commanded Ace to search.

Officer Keightley and Ace started walking around the Honda counter-clockwise. As Officer Keightley "was trying to present the passenger-side headlight[,]" Ace pulled toward the driver's side on two occasions. After Ace came around to the driver's side, he "bracketed"- i.e. , he moved his head in an attempt to locate an odor. Once Officer Keightley and Ace reached the driver's door, Ace stopped walking, put his forelegs on the driver's door, stuck his head into the Honda, and did a "focus sniff"- i.e. , closed his mouth and sniffed extremely rapidly.

Then, Ace sat, which Officer Keightley testified was an alert that the Honda was contaminated with, or had recently been contaminated with, drugs. The dog scan took thirty-seven seconds. While drug detection dogs may be trained to alert by staring, scratching, or biting at the source of the odor, Ace was trained to alert by sitting. On May 16, 2014, Officer Keightley received an e-mail from a member of the K-9 Unit with a recommendation by Officer McNerney concerning an issue as to the calculation of Ace's training hours.

Before receiving the e-mail, Officer Keightley would indicate in Ace's training records that he was trained for seven hours on one day each week. In the e-mail, however, Officer Keightley was advised that there was a new method of calculating the number of hours of Ace's training, and that Officer Keightley should count only the time from when the first narcotic aid was set to when the last test was conducted. Under the new calculation method, Ace had not received the sixteen hours of monthly training that was required for certification, and Officer Keightley and Ace were decertified. After Officer Keightley received the e-mail, he trained Ace on two additional days.

On May 19, 2014, Officer McNerney recertified Officer Keightley and Ace. The circuit court admitted Officer Keightley's and Ace's May 19, 2014 recertification into evidence. Officer Keightley testified that, after Officer McNerney recertified Ace, he usually trained Ace at least four days a week, for a total of sixteen to twenty hours a month. On cross-examination, Officer Keightley acknowledged that Ace had previously alerted to tobacco, air fresheners, a tennis ball, and the odor of "KONG" chew toys.

Officer Keightley also acknowledged that, at some point, Officer McNerney told Officer Keightley that, by standing still behind Ace, Officer Keightley was "cueing" Ace- i.e. , giving Ace a cue to take certain actions. Officer Keightley testified that he did not cue Ace during the dog scan of the Honda. Officer Keightley acknowledged that, in November 2013, Ace was trained only twice, for a total of three hours and fifteen minutes-calculated from when the first narcotic aid was set to when the last test was conducted. In February 2013, Ace was trained a total of eleven hours and nineteen minutes, calculated in the same way.

According to a summary of Ace's training records that Grimm's counsel had prepared, using the new formula for calculating the number of hours that Ace had been trained, Ace had not received the required sixteen hours of training in any month from July 2012 through 2014. Officer Keightley testified that this was so because the new formula for calculating the number of hours that Ace had been trained had not yet been implemented. Testimony of Sergeant Davis, One of the State's Experts As a witness for the State, Sergeant Davis testified that, in 1991, she became a handler with the K-9 Unit of the Montgomery County Police Department. Sergeant Davis testified that, initially as a handler, she managed five K-9 teams, and that throughout her career she managed both patrol K-9 teams and narcotics K-9 teams.

In 1998 or 1999, Sergeant Davis became a K-9 trainer. In 2001, Sergeant Davis placed in the top twenty K-9 officers in the United States Police Canine Association's Patrol Dog Field Trials. In 2008, Sergeant Davis was assigned as the K-9 unit's head trainer. During that time, she developed the K-9 Unit's current mandatory certification processes for patrol K-9s and narcotics K-9s, and trained the K-9 Unit's first firearms detection K-9 teams.

In 2009, Sergeant Davis began writing for Police K-9 Magazine. In that capacity, between 2009 and 2014, Sergeant Davis responded to questions about training dogs in Police K-9 Magazine. Sergeant Davis testified that she had run events at the United States Police Canine Association's national training seminar, and had given presentations at Police K-9 Magazine's conference. Sergeant Davis had trained a total of sixty-five K-9 patrol teams, and trained a total of thirty-six K-9 detection teams.

The parties stipulated that Sergeant Davis was an expert in K-9 training and handling. Sergeant Davis testified that she was not being paid for her testimony, apart from what she was paid for being on duty while testifying. Sergeant Davis explained that Maryland law does not require drug detection dogs to be certified, and that there are no State-wide requirements for drug detection dog performance. Although Maryland law does not require that drug detection dogs be certified, Sergeant Davis developed a process for certifying drug detection dogs in the Montgomery County Police Department's K-9 Unit.

Sergeant Davis testified that the K-9 Unit uses its best efforts to follow or exceed the standards that are recommended by the United States Police Canine Association. According to Sergeant Davis, the K-9 Unit trains drug detection dogs with both odor recognition tests and "environmental hides[,]" which are searches of buildings, vehicles, and parcels. Sergeant Davis described the process through which the Montgomery County Police Department's K-9 Unit trains drug detection dogs, to consist of: use of odors of controlled dangerous substances; distractions, such as dog food; and a reward, in the form of a ball on a rope. Sergeant Davis testified that the Maryland Transportation Authority Police's K-9 Unit's certification process generally comports with industry standards.

Sergeant Davis advised that the Montgomery County Police Department's K-9 Unit trains approximately twelve other local K-9 Units-including, at one point, the Maryland Transportation Authority Police's K-9 Unit. In August 2014, the Maryland Transportation Authority Police's K-9 Unit requested that members of the Montgomery County Police Department's K-9 Unit serve as judges in the Maryland Transportation Authority Police's K-9 Unit's certification process. Sergeant Davis and two other members of the Montgomery County Police Department's K-9 Unit served as judges. The certification process took place on August 19, 2014, and included a search of a vehicle, then a search of a parcel, and then a search of an indoor area.

Officer Keightley and Ace participated in, and were successful in, the certification process. According to Sergeant Davis, on one occasion during the certification process, Ace alerted to a vehicle containing a controlled dangerous substance, but Officer Keightley moved Ace so fast that they passed the vehicle that contained the controlled dangerous substance, and then moved to the next vehicle. At that time, Ace tried to get Officer Keightley to return to the original vehicle. Sergeant Davis referred to this situation as "a handler miss[,]" for which Ace was not responsible- i.e. , Officer Keightley missed Ace's alert.

Sergeant Davis stated that Ace had been "correct in his work." Sergeant Davis opined that the handler miss was not a basis for failure because, in any certification, one handler miss is permissible. Before testifying, Sergeant Davis reviewed Officer Keightley's and Ace's certifications, as well as Ace's training records from his initial training in 2012 to July 2014. Sergeant Davis testified that she did not observe any major changes in the process of training Ace, including the training routine and the types of narcotic aids that were used, between April 19, 2014-when the traffic stop occurred-and July 2014. Sergeant Davis testified that Officer Keightley and Ace performed satisfactorily during training.

Sergeant Davis testified that she was aware that Officer Keightley and Ace had been decertified in May 2014 as a result of the issue with the calculation of the number of Ace's training hours. Sergeant Davis testified that she would not have decertified Officer Keightley and Ace, as Ace's "skills ... were not affected one iota by the way" in which the Ace's training hours were calculated. Similarly, Sergeant Davis testified that the issue with regard to the calculation of the number of Ace's training hours did not affect Officer Keightley's and Ace's January 22, 2014 certification. Sergeant Davis explained: "Either [Ace] knows the odors[,] or he does[ not].

And he can perform, or he cannot." Sergeant Davis testified that she did not know of any other K-9 Unit that had decertified a handler and a drug detection dog "based on training hours." Sergeant Davis testified that, when a drug detection dog has not been trained for enough time, there is usually "an opportunity for remediation[,]" which Ace received. According to Sergeant Davis, in 2013, during Ace's training, he was placed in a total of 209 scenarios. Of those, Ace falsely alerted on 24 occasions. Sergeant Davis explained that she "expect[ed false alerts] to occur[,]" and that she did not think that any "particular amount" of false alerts was "acceptable or unacceptable." Sergeant Davis noted that there is no industry standard with regard to an unacceptable number of false alerts, and that the Montgomery County Police Department's K-9 Unit did not have such a standard.

Sergeant Davis testified that she "would look at each scenario and ask [ ] what is the cause of the" false alert. Sergeant Davis testified that Ace's false alerts during training were not "[s]ignificant" in light of the reasons for Ace's false alerts. According to Sergeant Davis, on multiple occasions, Ace falsely alerted when he was "asked to search for a very long time in an environment where there was no" controlled dangerous substance. Sergeant Davis opined that such environments were "counter-productive" because they simply provided Ace with "an opportunity to fail." During Sergeant Davis's testimony, the recording of the traffic stop from the dashboard camera in Sergeant Lamb's vehicle was played.

Addressing the circumstance that Ace did not alert as he passed by the passenger side, Sergeant Davis explained that Officer Keightley needed to ensure that Ace would pass by the Honda's occupants safely, and was probably tightly controlling Ace with his leash and with voice commands. Sergeant Davis opined that, although Ace "was clearly excited and [ ] wanted to work[,]" he appeared to be "in an obedient state" as he passed by the passenger side. Sergeant Davis observed that, once Officer Keightley and Ace reached the front of the Honda, Ace was barking and "still a little bit excited." Officer Keightley calmed Ace, and had Ace sit near him. Sergeant Davis noted that, after Officer Keightley gave the command to search, Ace immediately moved toward the driver's door.

With physical or verbal commands, Officer Keightley had Ace move toward the front right headlight. Ace briefly checked the front of the Honda, then moved toward the driver's door again. Again, Officer Keightley had Ace return to the front right headlight. Afterward, however, Ace moved toward the driver's door for a third time.

According to Sergeant Davis, while Officer Keightley was trying to direct Ace to the front right headlight, Ace independently insisted on moving to the driver's side. Sergeant Davis testified that Ace's behavior indicated that he had made an "independent discovery of" an odor of controlled dangerous substances, and was attempting to locate the source. Sergeant Davis testified that, while in front of the Honda, Ace engaged in "bracketing"- i.e. , whipping his head. Ace moved toward the driver's door and jumped on it "independently." Then, Ace lifted his head into the window, and engaged in "focus sniffing[.]" Sergeant Davis observed that, for six minutes during the traffic stop, the driver's door was open.

Sergeant Davis explained that the vehicles on Maryland Route 295 that were passing by the Honda "would create a vacuum and pull air[,]" as well as the odor of controlled dangerous substances, out of the driver's doorway. Sergeant Davis also noted that, because vehicles are climate-controlled, simply driving down a highway can "create odor pockets in places" that do not contain the source of the odor. Addressing Ace's alert near the driver's door, Sergeant Davis testified that Ace "was very firm in[,]" and "very committed in[,] his sit.... [Ace] held it very nicely." Sergeant Davis testified that Ace was not "unsure of himself" when he alerted. Sergeant Davis testified that the dog scan "took a very little bit of [ ] time" because "there was a lot of odor" and it was not "difficult for" Ace to identify the odor.

Sergeant Davis testified that the dog scan's length-thirty-seven seconds-was within Ace's "capacity to manage himself without" falsely alerting. Sergeant Davis testified that the recording of the traffic stop from the dashboard camera in Sergeant Lamb's vehicle contained no evidence that Ace's alert was false. Sergeant Davis explained that Ace's "work was very independent[,]" as evinced by the circumstance that Ace moved toward the driver's door on two occasions before Officer Keightley allowed him to go there. According to Sergeant Davis, Officer Keightley's "direction was more of a distraction than it was an influence on" Ace.

Sergeant Davis testified that Ace "already had clear identification of" the odor of a controlled dangerous substance, and that, when Ace alerted, he was indicating "that he knew there was odor there." Sergeant Davis advised that Officer Keightley did not cause Ace's alert "in any way, shape, or form[.]" Sergeant Davis testified that she did not see any evidence of cueing by Officer Keightley. Sergeant Davis testified that, to a reasonable degree of certainty, based on her training, knowledge, and experience as a K-9 trainer, Officer Keightley and Ace were "competent to be working the street and deploying, and making probable cause decisions on the street." Sergeant Davis testified that her opinion was "[b]ased on the totality of the circumstances, [and] looking at all of the training records" and having observed Officer Keightley and Ace on three occasions. On cross-examination, Sergeant Davis acknowledged that, before testifying, she had not reviewed Ace's field reports, which, according to her, did not have "as much bearing" as his training records, because Ace's training took place in environments that were more controlled than those in the field. Sergeant Davis explained that, in the field, "unintended cross-contamination" can occur.

Addressing the circumstance that, according to his field reports, Ace alerted 9 times when there was no discovery of drugs, and no admission that drugs had been in the vehicle, Sergeant Davis testified that that did not concern her "even in the least" and explained: "It[ i]s like putting garbage in a garbage can. And you take the garbage out[,] and you try to clean it, ... but you stick your head in that garbage can[,] and it still smells like garbage." Testimony of Cox, One of Grimm's Experts As a witness for Grimm, Cox-one of the people who provided Ace's initial training in 2012-testified that, in 1997, he joined the Baltimore Police Department's K-9 Unit as a handler. In 2000, Cox became the Baltimore Police Department's K-9 Unit's chief trainer. Cox trained a total of approximately eighty dogs.

In 2006, Cox left the Baltimore Police Department. In 2007, Cox became the Maryland Transportation Authority Police's K-9 Unit's only trainer. In October 2012, Cox left the Maryland Transportation Authority Police. The parties stipulated that Cox was an expert in K-9 training and handling.

Cox acknowledged that he was compensated for his travel and, additionally, that he was paid $200 an hour, and that he had earned approximately between $4,000 and $5,000 7 working on this case. Cox testified that, because he was being paid to testify, "apparently[, he] was not allowed to speak about the things that went on while [he] was employed [by] the State"-"[k]ind of like a gag order." Before testifying, Cox reviewed, among other documents, Ace's training records, his field reports, the Maryland Transportation Authority Police Narcotic/Explosive K-9 Certification Guidelines, and the recording of the traffic stop from the dashboard camera in Sergeant Lamb's vehicle. Similar to Sergeant Davis, Cox testified that Ace's training records were more important than his field reports. Cox testified that, in his opinion, after reviewing Ace's training records and the recording of the traffic stop, Ace was unreliable "at this point." According to Cox, the Maryland Transportation Authority Police's K-9 Unit had failed to maintain Ace's maintenance training for over a year.

Cox testified that once a drug detection dog is certified "[i]t takes a keen eye in order for a trainer ... to watch a dog perform and work and understand what the team is actually saying and doing. And in this case, it didn't happen." Cox testified that he felt that Officer Keightley was "basically, just like a rogue police." Cox opined that it was not Officer Keightley's fault, as the Maryland Transportation Authority Police's K-9 Unit did not "provide him a trainer to sit with him[,] because he's still green for a period of time[,] in order for him to gain the experience that was necessary." After being asked whether he noticed that there was a training session for Ace on November 12, 2012 and there was no other training session until December 12, 2012, Cox testified that, due to "the gag order[,]" he could not answer that. Cox indicated, however, that a drug detection dog should not go twenty or thirty days without being trained unless the officer is on extended leave. Cox noted that, when he went through the federal trainer certification, there was a distinction between "clock time" and "sniff time." According to Cox, sniff time is the time that a dog is actually engaged in performing scans.

Cox testified that, even if a law enforcement officer were at a training facility for eight hours, a drug detection dog might spend only a small portion of that time performing scans. Cox testified that he wanted to train his dogs to be as close to "100 percent as" he could. According to Cox, he "usually tr[ied] to hold [drug detection] dog[s] to a 95 percent ratio" and, if a dog dropped under 90 percent, he would "pull him off the road and find out why[.]" Cox indicated that, when a dog is being evaluated, he sets a standard to figure out if the dog "has a problem in falsing." Cox stated: "There's a percentage rate that I give, it's usually four percent." According to Cox, between April 15, 2013 and March 24, 2014, during Ace's training, he performed 179 scans. Of those, Ace falsely alerted to vehicles 15 times, and falsely alerted indoors 29 times, for a total of 44 false alerts.

Cox calculated that 4% of 179 scans is approximately 7.16. Cox stated that Ace's number of false alerts-44-is "five times over, or six times over [Cox's] allotted falsing." Cox acknowledged that, as Sergeant Davis testified, there are no State-wide requirements for drug detection dog performance. Cox opined, however, that Maryland should have such requirements. Cox testified that users of marijuana make blunts by sprinkling marijuana into tobacco leaves.

Cox explained that this circumstance can condition drug detection dogs to alert to the odor of tobacco. Cox testified that Ace's records showed that Ace had alerted on plastic and "indicated on blanks which is possibly human odor." According to Cox, this was "a red flag" and someone should have investigated what may have been going on with Ace. During Cox's testimony, the recording of the traffic stop from the dashboard camera in Sergeant Lamb's vehicle was played. Without specifically testifying that Ace was engaged in excessive barking, Cox asked that the video be paused and stated: "I usually don't like that excessive barking[.]" Cox testified that "excessive barking" "usually takes [ ] energy away from" a drug detection dog, and the dog then does not perform as well.

Cox stated that he "would actually want the officer to just calm the dog down" so that the dog would not be "coming into the field already exhausted." Cox testified that, according to the National Weather Service, on April 19, 2014, there was a four-mile-an-hour wind. Cox theorized that, "if we assume that, for argument's sake," the wind was "blowing from the bumper to the front bumper[,]" he would expect that, when he passed the passenger door, Ace would "whip his head around and catch some type of odor." According to Cox, if the wind were blowing in that direction, "there's enough that's going to plume out on the side," and Ace "should catch the odor when he passed the car passenger door." Cox noted that, even though Ace always started scans by going counterclockwise, on this occasion, he went in the other direction "on his own." Cox explained that Officer Keightley used a dog toy to motivate Ace to come to the headlight. Cox observed that, at that point, Officer Keightley was behind Ace. Cox observed that Officer McNerney had once told Officer Keightley that he was "cueing" Ace by standing still behind him.

Cox testified that he would not have "move[d Ace] unless he was ... actually performing his task[,]" and that, when Ace came "running around" to the driver's side, he did not "actively sniff at all." Cox opined that Ace "just jumped into object search" and then jumped onto the driver's door. Cox opined that Ace alerted to a "human scent[,]" which resulted from Grimm leaning on the driver's door. According to Cox, Ace was "imprinted on" human scent because, during his training, the narcotic aids were not properly maintained. Cox testified that Ace's training records contained no evidence that human scent had been used as a distracter-a substance that a drug detection dog is "extincted" off of during training.

Cox also opined that the narcotic aids were not replenished often enough to ensure that they were still "producing" a narcotics odor. Cox testified that, although there was evidence that Ace was trained to go to the source of an odor, he did not attempt to jump through the driver's door's window. Grimm's counsel asked whether it was significant that, after alerting, Ace turned his head toward Officer Keightley. Cox responded that this indicated that Ace was getting "weak in his field[,]" and that he was essentially asking Officer Keightley: "[D]id I [do] right?" When asked whether he observed any evidence of Ace "bracketing[,]" Cox responded: "No[.]" Cox opined that, based on his experience and expertise, "[t]here was no doubt in [his] mind that [Ace] was unreliable." As reasons for his opinion, Cox referenced "how many times [Ace had] falsed, what type of odors [Ace had] falsed on," "the human odor," "the lack of odor being produced by the narcotics [aids] that were set out," deficiencies in Ace's training, and the lack of "a certified trainer to ... watch [Ace] and make sure ... [that] the behavior that he[ was] offering in training [was] stopped at the appropriate time[.]" Cox also opined that Officer Keightley and Ace should have failed the certification process on August 19, 2014.

On cross-examination, Cox acknowledged that the Maryland Transportation Authority Police Narcotic/Explosive K-9 Certification Guidelines do not set a maximum percentage of false alerts of 5%. Cox also acknowledged that the Maryland Transportation Authority Police K-9 Standard Operating Procedures did not require analysis of the purity of narcotic aids. Cox testified: "I wish [that] I could speak about the steps and measures that I took [ ] to try to clear this up, but I[ am] not allowed to at this point. But if I could I would tell you what I tried to do." Testimony of Officer McNerney, One of Grimm's Experts As a witness for Grimm, Officer McNerney-one of the people who provided Ace's initial training in 2012-testified that, in 2006, he started working for the Transportation Security Administration's K-9 Unit.

Officer McNerney became a handler for an explosive detection dog. In 2009, Officer McNerney joined the Maryland Transportation Authority Police's K-9 Unit as a trainer. Initially, Officer McNerney trained dogs only in explosive detection. At that time, Cox was the head trainer, and Officers McNerney and McCarty were assistant trainers in explosive detection and drug detection, respectively.

In October 2012, Cox left the Maryland Transportation Authority Police, leaving only Officers McNerney and McCarty as trainers. In September 2013, Officer McCarty went on medical leave, and Officer McNerney assumed responsibility for training dogs in both explosive detection and drug detection. Officer McNerney testified that "it was tough" to train dogs in both explosive detection and drug detection. Officer McNerney testified that he went to command and asked that training explosive and drug detection dogs be made a full-time position, but his request was denied.

Officer McNerney testified that, "numerous times," he communicated to his command staff that he was available only ten of the twenty-six training days between September 2013 and March 2014, and that handlers did not show up for training on eight of the days when he was not present. On March 11, 2014, Officer McNerney stepped down as a trainer because he did not "want the liability" and because he was concerned that the drug detection and explosive detection dogs were not proficient because they were not being trained. In May 2014, however, Officer McNerney "was ordered back" to the K-9 Unit as part of "a full-time position." The circuit court admitted Officer McNerney as an expert in the field of K-9 training and handling. Officer McNerney was responsible for Officer Keightley's training from September 2013 through March 2014.

Officer McNerney testified that he determined that Ace had "a lot of [ ] issues" as to false alerts, and that Ace was not trained for the required amount of time. According to Officer McNerney, Ace had a "pretty high" number of false alerts, and he extended to Officer Keightley an offer to train Ace, but Officer Keightley did not "show up to train on those days[.]" According to Officer McNerney, the purpose of such training would be to "proof" Ace off of such sources of odor as air fresheners and tobacco. Contrary to Officer Keightley's testimony, Officer McNerney testified that, between September 2013 (when Officer McNerney assumed responsibility for training dogs in both explosive detection and drug detection) and April 19, 2014 (the date of the traffic stop), Ace was not trained seven hours a week, or sixteen hours a month. Officer McNerney testified that, between those dates, he trained Ace only ten times.

Officer McNerney testified that, according to Ace's training records, between those dates, Ace was not trained the required sixteen hours a month that was required for certification. On May 17, 2014, pursuant to Officer McNerney's recommendation, Officer Keightley and Ace were decertified. Two days later, on May 19, 2014, Officer Keightley and Ace were recertified. At some point during Ace's training, Officer McNerney noticed that Officer Keightley was cueing Ace.

According to Officer McNerney, because Officer Keightley knew where the narcotic aids were, he cued Ace by subconsciously slowing down and walking behind him. Officer McNerney opined that it was a disfavored practice for handlers to set the narcotic aids, as that can lead to cueing. Officer McNerney also testified that he believed that the narcotic aids had not been "switched out" since 2009. Officer McNerney opined that it was important to use fresh narcotic aids during training.

Officer McNerney opined that, as of March 11, 2014, when he resigned, Ace was unreliable "[b]ased on ... the falsing issues compared to the training that was conducted from the previous-the previous trainer had set the requirements of [90%] and [Ace] fell below that [90%] range where, if he wasn't reliable." Officer McNerney acknowledged that, to be certified by the K-9 Unit, a drug detection dog need only score 87.5%. Officer McNerney opined, however, that he held drug detection dogs to a higher standard in training because, unlike scans in the field, training takes place in controlled environments. Officer McNerney agreed with Sergeant Davis that the "handler miss" was not a basis for failure of the August 19, 2014 certification process. On cross-examination, Officer McNerney acknowledged that, on January 22, 2014, he conducted a certification test, which Officer Keightley and Ace passed; and, on that date, he approved the certification.

Officer McNerney acknowledged that Officer Keightley and Ace were not decertified before April 19, 2014- i.e. , that the certification was valid when the traffic stop occurred. Circuit Court's Ruling and Findings After hearing arguments by counsel, the circuit court denied the motion to suppress, finding as follows: Grimm was driving the [Honda]. It had the Georgia plates; it was here in Anne Arundel County. [ ] Chase was a passenger, as well as [Henry]. And[,] back on April 19[,] 2014, Sergeant Lamb received some type of be[-]on[-]the[-]lookout, ... from his contacts in [the Drug Enforcement Administration] and [the High Intensity Drug Trafficking Area]. * * * [ ] Sergeant [Lamb stopped] the [Honda], and[,] unfortunately for [ ] Grimm and [ ] Chase and [Henry], none of them were wearing seat[ ]belts, which gave [ ] Sergeant [Lamb] th[e] reasonable suspicion that he needed to conduct the traffic stop[.] * * * At the [Honda], before [Ace] arrives[, t]here is the discussion about Atlanta and airline tickets[,] and [ ] Grimm puts his head on the pillow[,] and he leans with [his left] foot out of the [Honda], and the [back]seat passenger, [ ] Chase, is overly talkative, and [Henry] is not talkative.

And all of those things go into [ ] Sergeant [Lamb]'s mind[,] and[,] in his mind[,] they are all indicia that he has someone who is a drug dealer, the nervousness and all that stuff. * * * [A]bsent [Ace's] alert, ... I would not have found probable cause. I would not have found [ ] Atlanta being a source city, the nervousness, the airline[ ] tickets to be enough to get into the [Honda]. So, this case rightly turns on Officer Keightl[e]y and [ ] Ace.

Not surprisingly[,] we have a divergence of views and a difference of opinion as to what the Court should consider to be credible. It will spoil the ending when I tell you who[m] I find to be the most credible witness. But I cannot analyze this case without telling you who[m] I find to be the most credible witness. Because[,] when I discuss Officer Keightl[e]y, he [and Ace were] certified at the time of the [traffic] stop and the [dog] scan.

And [Officer Keightley and Ace were] certified on January 22[ ], 2014, and it was[ not] until about a month after that [when they] lost [their] certification, and it was[ not] too long after that before the certification was restored to [them]. [Officer Keightley] used all the proper terminology[-]bracketing, focus sniffing, response, et cetera. And [Officer Keightley] was certified and qualified as an expert in this area. And the Court has found [Officer Keightley] credible, but that[ is] not necessarily the ultimate finding because I have witnesses with expertise [that is] vastly superior to his. And I must analyze that before I can come back to Keightl[e]y to determine whether he did something [that] was proper or improper.

I found [Officer Keightley] credible[,] and I found him [and Ace] to be certified[,] and I considered his training as to be in compliance or not in compliance with standard operating procedures. This is a fuzzy area. Sergeant [ ] Davis and [ ] Cox and [ ] Officer McNerney presented different views of what the standard operating procedures should be. Each department writes their own standard operating procedures.

Each department prepares their own standard operating procedures. And each department decides what their standard operating procedures shall be so that their K-9 officers-well, handlers, and the dogs and the trainers are certified. Sergeant Davis has a different view than [ ] Cox does of what the ultimate standards should be, but there are standards in place. And [ ] Maryland has not ad[o]pted rigid standards.

I think that[ is] what Florida v[ ]. Harris[, 568 U.S. 237 , 133 S.Ct. 1050 , 185 L.Ed.2d 61 (2013),] was telling us. So, the question for the Court is, were those standards that were in place appropriate? And I think that they were.

I find that there were. Was there compliance with those standards? That[ is] the second part of that issue. We have to look at the hours, we have to look at the [narcotic] aids, and we have to look at whether or not the training was in compliance with the standard operating procedures, and was there a significant or serious enough deviation to say that [Ace] or [Officer Keightley] was not competent to provide the work in the field.

And we can analyze the 51 alerts, the 19 [false alert]s. And we can analyze what it ... was due to[,] and the reasons behind it. We can look at the extended time, the distance for the training exercises, the staleness of the [narcotic] aids, et cetera. And[,] to do that, the Court has to look to the experts.

And the experts are Sergeant [ ] Davis and [ ] Cox. [ ] Cox is in a perilous position at times[,] and I do think [that] he walked that tightrope that he was presented appropriately. I do not find that he strayed over any line. And I think that his answers were credible in terms of what he said and how he said it. [Cox] and [ ] Officer McNerney are very close in their views. They are good and fair in their analysis.

And while [Cox] is retired and [Officer McNerney] is an active [law enforcement] officer, they presented to the Court what appeared to be their view of what the optimum standards should be.... I am convinced that there is dissension in the ranks. And I think that some of this was an airing of dirty laundry. But there appears to be almost a[ "]they did[ not] do it today as I did it then["] view from [ ] Cox.

And there seemed to be from Officer McNerney, ["]you[ are] not listening to me.["] Having said that, they[ are] both credible. There is some bias, but they are credible and they have presented credible testimony. The Court will comment on Sergeant [ ] Davis. I find [Sergeant Davis] to be the most credible witness....

I find [Sergeant Davis's] qualifications, her knowledge, [and] her training and experience to be impeccable. Again, I[ am] going to spoil the ending, but I find her to be the most credible witness[,] and it is she who[m] I rely upon the most and find to be the best and most objective observer. [Sergeant Davis's] comments, and I hope [that] I quote this correctly, have stuck with me ever since she said it. And when I went over and examined everything and everything over and over and over again, I could not get this comment out of my mind. ["Ace] knows the odor[,] or he does[ not]. He can perform[,] or he can[not."] And[,] with that in mind, I find [Sergeant Davis] to be a witness who has no ties to th[is] case, neutral and unbiased and has-I find she has no issue with [Officer Keightley] or [Ace].

And I find [Sergeant Davis's] analysis of the [traffic] stop and [Ace]'s actions to be credible. [Sergeant Davis] explains, ... succinctly and carefully and expansively at times[,] the issues with [false alerts] or certification or protocols to the satisfaction of the Court that I can find Officer Keightl[e]y and [ ] Ace to be credible and to be a certified [drug detection] dog that the Court can rely upon for assessing whether or not probable cause exist[ed]. When the Court analyzes Sergeant Lamb's observations, comments, the [Drug Enforcement Administration] tip with [Ace] or, which I find credible, I find probable cause ... to believe that there is a reasonable probability and/or a fair probability that contraband [would] be found in [the Honda]. * * * I disagree with [ ] Officer McNerney and [ ] Cox that there was no alert by [Ace]. I[ am] not an expert. I must analyze it on the totality of the circumstances.

And I must rely upon the expert testimony. And I find the most credible expert to be Sergeant [ ] Davis. When she broke the [traffic] stop down and she went, "[ ]lead is tight to prevent [Ace] go in window, shows dog [Ace] has independent intention from [Officer Keightley]'s [in]tention. [Ace] insists to go to driver's [ ] door not once, two time[s]. Indicates target odor, get[s] to source. [Officer Keightley] took control dog leash tight, not have contact with civilian's dog, excited, wants to work. [Ace] obedience, stay, lose heel, not expect indication." Then[,] when [Sergeant Davis] goes through all of this[,] she concludes [that] there might have been a little odor, there might have been a lot of odor, but [Ace] alerted.

And she concludes that [Ace] committed, sat, held it nicely[, that] there was no evidence of a false alert, [and] that [Ace] was independent. [Officer Keightley] was more of a distraction. [Ace] knew the odor, there was no [ ] interference[ by Officer Keightley], no cueing from [Officer Keightley]. There was an obvious change of behavior, the head dip, the bracketing, the focused sniffing. That[,] in [Sergeant Davis's] opinion[,] the competence of [ ] Ace was that he was competent to make [a] probable cause decision based upon the training records, observing the team personally[,] and reviewing the video. The Court accepts that[,] and the Court finds that to be the most credible evidence in the case.

(Emphasis added). Conviction and Opinion of the Court of Special Appeals On July 7, 2015, Grimm pled guilty to possession of heroin with intent to distribute, on the condition that he could appeal the circuit court's denial of the motion to suppress. On August 4, 2015, Grimm noted an appeal. On April 26, 2017, the Court of Special Appeals affirmed the conviction.

See Grimm v. State , 232 Md. App. 382 , 386, 158 A.3d 1037 , 1039 (2017). The Court of Special Appeals held that an appellate court reviews for clear error a trial court's determination as to whether a drug detection dog is reliable. See id. at 403 , 158 A.3d at 1050 . The Court of Special Appeals explained: Whether Ace was-at the time of the [dog] scan of Grimm's vehicle-a well-trained or reliable [drug detection] dog, whose alerts could be relied upon by Officer Keightley as indicating that there was a fair probability that [Grimm's] vehicle contained one of illegal drugs [that] Ace had been trained to detect, was a question of fact [that was] properly committed to the adjudicatory skill of the [trial court that] heard the evidence [that was] presented at the hearing on the motion to suppress.

An appellate court is ill-equipped to determine the proper amount of weight to be given to various pages of the extensive documentation in evidence regarding a [drug detection] dog's performance during training exercises, or to evaluate the credibility of witnesses, or weigh the conflicting testimony of experts. Such factual determinations are best left to the [trial court that] hears the evidence, and are best reviewed under a "clearly erroneous" standard that gives deference to [the trial court]'s superior opportunity to evaluate credibility and weigh the evidence. Id. at 403-04 , 158 A.3d at 1050 (citations omitted). Addressing the merits, the Court of Special Appeals rejected Grimm's contention that the circuit court clearly erred in making certain findings of fact, such as the circuit court's finding that Sergeant Davis was the most credible witness.

Id. at 404-05 , 158 A.3d at 1050 -51 . The Court of Special Appeals also rejected Grimm's assertion that, in light of alleged evidence of deficiencies in Ace's training, the circuit court clearly erred in finding that Ace was reliable. See id. at 406-07 , 158 A.3d at 1051 -52 . The Court of Special Appeals observed that Ace and Officer Keightley were decertified for only two days, and that Sergeant Davis testified that she would not have decertified Ace and Officer Keightley.

See id. at 406-07 , 158 A.3d at 1052 . The Court of Special Appeals rejected Grimm's contention that Officer Keightley and Ace were not "meaningful[ly]" certified at the time of the dog scan of his vehicle in April 2014, noting that Officer Keightley and Ace had been certified in January 2014, and that certifications are valid for six months. See id. at 407 , 158 A.3d at 1052 . The Court of Special Appeals rejected Grimm's argument that the video of the dog scan showed that Ace did not alert, as the circuit court credited Sergeant Davis's testimony that Ace alerted.

See id. at 407 , 158 A.3d at 1052 . The Court of Special Appeals was unpersuaded by Grimm's reliance on Cox's testimony that Ace had 44 false alerts in 179 training scenarios, as Sergeant Davis analyzed a different time period, found a much lower rate of false alerts, and "testified that there was no particular amount of false alerts that she would find unacceptable." Id. at 407 , 158 A.3d at 1052 . 8 Petition for Writ of Certiorari and Cross-Petition On June 15, 2017, Grimm filed a petition for a writ of certiorari , raising the following two issues: 1. When a defendant challenges the reliability of a drug-sniffing dog overall and the reliability of the dog's purported alert to the possible presence of drugs in a vehicle driven by the defendant, in accordance with [ ] Harris , 568 U.S. 237 [, 133 S.Ct. 1050 ], and the trial court rules that the dog's alert established probable cause to search the vehicle, what is the applicable standard of appellate review? 2. Whatever standard of appellate review applies, did the [circuit] court err in ruling that [law enforcement] had probable cause to search the [Honda that was] driven by [Grimm]?

On June 30, 2017, the State filed a conditional cross-petition for a writ of certiorari , raising the following issue: "Even if [law enforcement officers] did not possess probable cause to search Grimm's [Honda], should this Court decline to apply the Fourth Amendment's exclusionary rule because the [law enforcement officers] relied on Ace's [ ] alert in objective good faith?" On September 12, 2017, this Court granted the petition and the conditional cross-petition. See Grimm v. State , 456 Md. 54 , 170 A.3d 290 (2017). DISCUSSION I. The Parties' Contentions Grimm contends that the Court of Special Appeals erred in reviewing for clear error the circuit court's determination that Ace was reliable, and argues that the correct standard of review is de novo - i.e. , without deference. Grimm asserts that the appellate court must review without deference the issue of whether a drug detection dog is reliable because an appellate court reviews without deference the issue of whether probable cause existed.

Grimm maintains that a trial court is not better positioned than an appellate court to determine whether a drug detection dog is reliable. Grimm contends that the circuit court did not have an advantage in assessing the expert testimony because the experts' credibility turned not on the experts' demeanor, but rather on the plausibility and coherence of the experts' explanations of the relevant documents and the recording of the traffic stop. Grimm argues that it would be inappropriate to defer to the circuit court's determination of the experts' credibility because the experts' opinions essentially constituted opinions as to whether probable cause existed. Grimm maintains that, even if the circuit court had an advantage in weighing the evidence, to maintain control of the probable cause standard and satisfy the Fourth Amendment, an appellate court must still review without deference the circuit court's determination that Ace was reliable.

Grimm contends that, because there are no generally accepted standards in Maryland regarding the training and certification of drug detection dogs, appellate courts must provide guidance to law enforcement agencies on the issue, and review without deference would provide the opportunity for such guidance. Grimm asserts that, if appellate courts review trial courts' reliability determinations for clear error, then a drug detection dog might be considered reliable in one county or one courtroom, but not another. Grimm maintains that, in Harris , 568 U.S. 237 , 133 S.Ct. 1050 , the Supreme Court analyzed the issue of whether a drug detection dog was reliable in a manner that was consistent with review without deference. The State responds that an appellate court reviews a determination of probable cause in the same manner in all warrantless search cases, regardless of whether a law enforcement officer or a drug detection dog detected an odor of controlled dangerous substances.

The State contends that an appellate court reviews for clear error a trial court's findings of fact, and reviews without deference the ultimate question of whether probable cause existed. The State argues that the relevant finding of fact is whether a drug detection dog detected an odor of controlled dangerous substances. The State asserts that, just as an appellate court defers to a trial court's finding that a law enforcement officer was credible in testifying that he or she smelled marijuana emanating from a vehicle, an appellate court defers to a trial court's factual finding that a drug detection dog smelled drugs. The State maintains that the only difference in a case that involves a drug detection dog is that the State must prove that the drug detection dog smelled drugs through circumstantial evidence, such as the drug detection dog's training and performance in the field.

The State argues that, in Harris , the Supreme Court applied the well-established standard of review of a determination of probable cause, and did not apply a different standard of review because a drug detection dog, rather than a law enforcement officer, detected drugs. Law In Miller , 474 U.S. at 105 , 110 , 106 S.Ct. 445 , the Supreme Court held that the issue of whether a confession was voluntary was a legal question, not a factual question that was entitled to the presumption of correctness that was afforded to State court factual findings under what was then 28 U.S.C. § 2254 (d). The Supreme Court concluded that there was no support for the position that the enactment of what was then 28 U.S.C. § 2254 (d) in 1966 altered the Court's prior cases holding that the issue of voluntariness is a legal question. See id. at 111 , 106 S.Ct. 445 .

In Miller , id. at 106-07 , 106 S.Ct. 445 , while interviewing a defendant, a law enforcement officer made false statements and "stated that he did not consider [the defendant] to be a criminal because the perpetrator of the [murder] had a 'mental problem[,]' and needed medical help rather than punishment." The defendant confessed, and was convicted. See id. at 107-08 , 106 S.Ct. 445 . The defendant appealed, contending that his confession was involuntary. See id. at 108 , 106 S.Ct. 445 .

A State supreme court determined that the defendant's confession was voluntary. See id. Later, the defendant petitioned for a writ of habeas corpus. See id.

The United States District Court for the District of New Jersey dismissed the petition, and the United States Court of Appeals for the Third Circuit affirmed, concluding that the District Court's dismissal of the petition was proper because the issue of whether a confession was voluntary was a factual question. See id. The Court of Appeals concluded that the habeas proceeding was governed by what was then 28 U.S.C. § 2254 (d), which stated in pertinent part: "In any proceeding instituted in a Federal Court by an application for writ of habeas corpus by a person in custody pursuant to the judgment of a State court, a determination after a hearing on the merits of a factual issue, made by a State court of competent jurisdiction shall be presumed to be correct[.]" Id. at 108 , 105 n.1, 106 S.Ct. 445 . 9 The Supreme Court reversed, explaining that its precedent established that "the ultimate issue of voluntariness is a legal question requiring independent federal determination." Id. at 109-10 , 106 S.Ct. 445 (cleaned up). In other words, the Supreme Court "was not bound by a [S]tate-court voluntariness finding[,]" and had a "historic duty to make an independent evaluation of the record." Id. at 110 , 106 S.Ct. 445 (cleaned up).

The Court acknowledged that "subsidiary factual questions, such as whether a drug has the properties of a truth serum, or whether in fact [law enforcement officers] engaged in the intimidation tactics [that are] alleged by [a] defendant, are entitled to the [ 28 U.S.C.] § 2254(d) presumption." Id. at 112 , 106 S.Ct. 445 (citations omitted). The Court, however, reiterated that "the ultimate question whether, under the totality of the circumstances, the challenged confession was obtained in a manner compatible with the requirements of the Constitution is a matter for independent federal determination." Id. at 112 , 106 S.Ct. 445 . The Court observed that "the appropriate methodology for distinguishing questions of fact from questions of law has been, to say the least, elusive." Id. at 113 , 106 S.Ct. 445 (citations omitted). The Court distinguished factual questions from legal questions as follows: Perhaps much of the difficulty in this area stems from the practical truth that the decision to label an issue a "question of law," a "question of fact," or a "mixed question of law and fact" is sometimes as much a matter of allocation as it is of analysis.

At least in those instances in which Congress has not spoken[,] and in which the issue falls somewhere between a pristine legal standard and a simple historical fact, the fact/law distinction at times has turned on a determination that, as a matter of the sound administration of justice, one judicial actor is better positioned than another to decide the issue in question. Where, for example, as with proof of actual malice in First Amendment libel cases, the relevant legal principle can be given meaning only through its application to the particular circumstances of a case, the Court has been reluctant to give the trier of fact's conclusions presumptive force and, in so doing, strip a federal appellate court of its primary function as an expositor of law.... [By] contrast, other considerations often suggest the appropriateness of resolving close questions concerning the status of an issue as one of "law" or "fact" in favor of extending deference to the trial court. When, for example, the issue involves the credibility of witnesses[,] and therefore turns largely on an evaluation of demeanor, there are compelling and familiar justifications for leaving the process of applying law to fact to the trial court and according its determinations presumptive weight. Id. at 113-14 , 106 S.Ct. 445 (emphasis added) (citations omitted).

Significantly, the Court stated that "an issue does not lose its factual character merely because its resolution is dispositive of the ultimate constitutional question." Id. at 113 , 106 S.Ct. 445 (citation omitted). In Ornelas v. United States , 517 U.S. 690 , 691, 116 S.Ct. 1657 , 134 L.Ed.2d 911 (1996), the Supreme Court held that the ultimate questions of reasonable suspicion and probable cause are to be reviewed de novo. The Supreme Court stated that the "principal components" of the inquiry are a determination of the events leading up to the stop or search, and a determination of whether these "historical facts" viewed from the standpoint of an objectively reasonable officer give rise to reasonable suspicion or probable cause. Id. at 696 , 116 S.Ct. 1657 .

In Ornelas , id. at 691-92 , 116 S.Ct. 1657 , a law enforcement officer observed a two-door General Motors vehicle with California license plates in the parking lot of a motel in Milwaukee. The vehicle "attracted [the officer]'s attention ... because older model, two-door General Motors [vehicle]s are a favorite [among] drug couriers [as] it is easy to hide things in them; and because California is a 'source State' for drugs." Id. at 692 , 116 S.Ct. 1657 . The officer radioed a dispatcher, and learned that the vehicle's registered owner was one of the two defendants. See id.

The officer also learned that, at 4 a.m., the other defendant, accompanied by another man, had checked into the hotel without a reservation. See id. The officer and his partner contacted the Drug Enforcement Administration, and learned that, according to the Narcotics and Dangerous Drugs Information System, one of the defendants was a heroin dealer from California, while the other defendant was a cocaine dealer from Arizona. See id.

The officers summoned a drug detection dog and his handler; however, no dog scan of the vehicle occurred. See id. The defendants left the motel and entered the vehicle. See id.

One of the officers approached the vehicle, identified himself, and asked whether the defendants had any drugs or other contraband. See id. The defendants responded: "No." Id. The officer asked for, and received, the defendants' identification.

See id. at 692-93 , 116 S.Ct. 1657 . The officer asked for permission to search the vehicle, and the defendants consented. See id. at 693 , 116 S.Ct. 1657 . Another officer-who had searched approximately 2,000 vehicles for drugs-searched the vehicle, and noticed that a panel above the passenger-side backseat armrest felt somewhat loose.

See id. According to the officer, a screw in the doorjamb that was next to the panel was rusty, indicating that it had been removed at some point. See id. The officer dismantled the panel, and found cocaine inside.

See id. The defendants moved to suppress the cocaine, contending that the officers violated the Fourth Amendment by detaining them in the motel's parking lot and searching the vehicle's panel without a warrant. See id. The government conceded that the officers initiated an investigatory stop when they approached the defendants.

See id. A magistrate judge determined that the officers had reasonable suspicion to initiate the investigatory stop, but lacked probable cause to search the vehicle. See id. at 694 , 116 S.Ct. 1657 . The United States District Court for the Eastern District of Wisconsin determined that the officers had both reasonable suspicion to initiate the investigatory stop and probable cause to search the vehicle, and concluded that "reasonable suspicion became probable cause when [the officer] found the loose panel." See id.

The United States Court of Appeals for the Seventh Circuit concluded that it would reverse "the District Court's determinations of reasonable suspicion and probable cause ... only upon a finding of 'clear error.' " Id. (cleaned up). The Court of Appeals reasoned that the District Court's determination of reasonable suspicion was not clearly erroneous, but remanded for a determination of whether the officer was credible in testifying about the panel. See id. at 695 , 116 S.Ct. 1657 .

On remand, the magistrate judge expressly found the officer's testimony credible, and the District Court again determined that probable cause existed. See id. The Court of Appeals affirmed, reasoning that the District Court's determination of probable cause was not clearly erroneous. See id.

Significantly, the Supreme Court reversed and remanded the case to the Court of Appeals with instructions to review the District Court's determinations of reasonable suspicion and probable cause without deference. See id. at 700 , 116 S.Ct. 1657 . The Supreme Court distinguished factual questions from legal questions, in the context of determinations of probable cause and reasonable suspicion, as follows: The principal components of a determination of reasonable suspicion or probable cause will be the events [that] occurred leading up to the stop or search, and then the decision whether these historical facts, viewed from the standpoint of an objectively reasonable [law enforcement] officer, amount to reasonable suspicion or to probable cause. The first part of the analysis involves only a determination of historical facts, but the second is a mixed question of law and fact: The historical facts are admitted or established, the rule of law is undisputed, and the issue is whether the facts satisfy the relevant statutory or constitutional standard, or[,] to put it another way, whether the rule of law[,] as applied to the established facts[,] is or is not violated.

Id. at 696-97 , 116 S.Ct. 1657 (cleaned up). The Supreme Court also discussed "background facts" as follows: A trial [court] views the facts of a particular case in light of the distinctive features and events of the community; likewise, a police officer views the facts through the lens of his police experience and expertise. The background facts provide a context for the historical facts, and when seen together yield inferences that deserve deference. For example, what may not amount to reasonable suspicion at a motel located alongside a transcontinental highway at the height of the summer tourist season may rise to that level in December in Milwaukee.

That city is unlikely to have been an overnight stop selected at the last minute by a traveler coming from California to points east. The 85-mile width of Lake Michigan blocks any further eastward progress. And while the city's salubrious summer climate and seasonal attractions bring many tourists at that time of year, the same is not true in December. Milwaukee's average daily high temperature in that month is 31 degrees and its average daily low is 17 degrees; the percentage of possible sunshine is only 38 percent.

It is a reasonable inference that a Californian stopping in Milwaukee in December is either there to transact business or to visit family or friends. The background facts, though rarely the subject of explicit findings, inform the [trial court]'s assessment of the historical facts. Id. at 699 , 116 S.Ct. 1657 . The Supreme Court observed that it had never expressly deferred to a trial court's determination of reasonable suspicion or probable cause.

See id. at 697 , 116 S.Ct. 1657 . The Supreme Court stated that, "as a general matter[,] determinations of reasonable suspicion and probable cause should be reviewed [without deference]