Sugarman v. Liles

Adkins, J. This case presents yet another opportunity for clarification of when epidemiological studies relied upon by an expert provide a sufficient factual basis for the expert's testimony. Specifically, we shall consider whether an expert's opinion on causation, relying on epidemiological studies, suffers from the same "analytical gap" identified in Rochkind v. Stevenson , 454 Md. 277 , 164 A.3d 254 (2017). We shall also assess whether an expert may offer an opinion on specific causation when relying on epidemiological data coupled with an individualized analysis of the plaintiff and his claimed injuries. Finally, we consider the sufficiency of proof required for a plaintiff to demonstrate a loss of earning capacity.

BACKGROUND Respondent, Chauncey Liles, Jr. sued Ivy Realty, Inc. and Stanley Sugarman (collectively "Sugarman") in the Circuit Court for Baltimore City. Liles alleged injury and damages caused by lead paint exposure at a residential property (the "Residence") owned by Sugarman. At trial, the parties stipulated that, due to Sugarman's negligence, Liles was exposed to deteriorating lead paint at the Residence. The parties further stipulated that the exposure caused Liles's elevated blood lead levels ("BLL").

The only remaining questions for the jury were whether the lead exposure caused Liles any injury, and if so, what damages he incurred. Liles's Developmental History Liles was born in 1998. At the age of 2, Liles's BLL measured 11 mcg/dL. At the age of 3, his BLL was 10 mcg/dL.

When he entered the fourth grade, Liles began to have educational difficulties. At the same time, Liles was experiencing grief and anxiety from the death of several family members. His educational records reflect that in fifth grade, as a result of his educational difficulties, his teachers provided additional accommodations, including one-on-one support, individualized help on his math skills and test taking practice, additional response time in class, additional time to complete assignments, and repetition of directions. Through middle school, Liles earned grades in the 90s, 80s, and mid-to-high 70s.

After middle school, Liles attended Baltimore City College ("City College"), a selective high school located in Baltimore. He graduated in May 2016. In 2012, Liles broke the thumb on his dominant hand. In 2012 and 2013, his academic performance faltered.

Initially, in a deposition, Liles attributed this dip in his grades to not being able to write with an injured hand. At trial though, he testified that this was just an excuse meant to cover for his faltering performance and difficulties paying attention. In 9th grade, his GPA was 2.38. In 10th grade, he had a GPA of 1.09.

His GPA increased in 11th and 12th grade, when he earned GPAs of 2.57 and 3.36 respectively. He graduated 194th out of 301 students in his class. Liles described his grades at City College as "terrible." He attributed his performance to his inability to focus and claimed that he is easily distracted, has difficulty sitting still, and stated that he "just can't grasp things as fast as other people do." He claimed that these issues started when he was young and that "as the work got harder, [he] couldn't get it." Despite these difficulties in the classroom, Liles tested at or above grade level on the Maryland School Assessment and passed his High School Assessment without any additional support. Liles was accepted at West Virginia University and Bowie State University, both of which are four-year schools.

At trial, Liles testified that he intended to pursue a bachelor's degree from Bowie State. Liles's mother graduated from high school and obtained some college education, but has no college degree. His father also graduated from high school but did not attend college and works as a truck driver. Expert Testimony At trial, Liles called four expert witnesses: (1) Robert Kraft, Ph.D.; (2) Jacalyn Blackwell-White, MD; (3) Mark Lieberman; and (4) Michael Conte, Ph.D. We shall examine the testimony of each in turn.

Robert Kraft, Ph.D. Liles offered Dr. Robert Kraft as an expert in the field of psychology and neuropsychology. Dr. Kraft testified that he conducted a neuropsychological examination of Liles, which consisted of an interview as well as several tests administered to assess various aspects of intelligence including attention, memory, learning, and language. Specifically, Dr. Kraft administered an IQ test, the Wechsler Adult Intelligence Scale ("WAIS-IV"). Dr. Kraft testified that Liles had a full-scale IQ of 94, which placed him in the 34th percentile and in the normal range.

Dr. Kraft also explained that an average range IQ does not necessitate a conclusion that there was no evidence of brain impairment. In addition to this overall score, the IQ test revealed several sub-scores, which measured various aspects of intelligence. Dr. Kraft found a "statistically significant" discrepancy between some of Liles's sub-scores, which indicated that Liles had some form of brain impairment. Liles received a sub-score of 86 on two indexes Dr. Kraft identified as most sensitive to attention and concentration.

Notably, according to Dr. Kraft, Liles scored 86 in both: (1) auditory encoding of information in the working memory; and (2) information processing speed. Dr. Kraft testified that these are both factors of attention. Dr. Kraft described auditory encoding in the following manner: "Any time an individual gives you a piece of information that you are expected to use in some way, you are encoding that information until you've completed the task, then you can forget about the information." Regarding information processing speed, Dr. Kraft said: Processing speed is your ability to independently focus and complete a task in a self-direct manner. So any time a student sits down to study, an adult, anyone sits down to read a book, any time a person sits down to complete a writing task-that requires information processing speed.

When Dr. Kraft tested Liles's information processing speed a second time, Liles received a scale score of 76, which placed him in the 5th percentile. Liles also performed in the "borderline" range on a test related to "simple and complex visual motor tracking." This, Dr. Kraft testified, was "consistent with his processing speed difficulty and difficulty shifting attention." Dr. Kraft opined that Liles's lower scores on these tests of attention were statistically significant and attributable to brain impairment. The lower scores on auditory encoding and information processing speed were the only impairments Dr. Kraft identified. On cross-examination, when asked about how these attention impairments related to Liles's academic performance, Dr. Kraft said, "[h]e could, in fact, have these deficits but still [have] B's all the way through [school].

These deficits are mild, and they may not always show up in every school year." He further stated, that "[m]y opinion ... is that he may not show any impairments in his school performance at all based on these deficits, if he's able to adapt and accommodate in some way for them." Jacalyn Blackwell-White, MD Dr. Blackwell-White was accepted as an expert in the fields of pediatrics and childhood lead poisoning. She testified that lead is a neurotoxin that "causes damage to the central nervous system." She explained that lead blocks the transmission of neurotransmitters to the brain, which impedes "learning pathways." Lead exposure during the prenatal stage through at least age six or seven can cause damage to the brain because it disrupts the learning pathways during critical developmental periods. Dr. Blackwell-White testified that this means that "attention is going to be affected." She also explained that the Center for Disease Control "issue[s] standards and protocols for diagnosis and treatment of children who have elevated blood lead levels ..." and has set the current reference level at 5 mcg/dL. The reference level was once higher, but later lowered due to medical studies showing that BLLs under 10 mcg/dL are harmful to children.

Dr. Blackwell-White did not examine Liles, but instead reviewed his medical records, Dr. Kraft's report, and other associated records. She opined that, "within a reasonable degree of medical certainty," Liles "was exposed to sustained toxic blood lead levels at an early age.... [and] [h]is documented period of toxicity was at least 12 months." Liles "incurred brain impairment as a result of his early lead toxicity...." This impairment included, but was not limited to, a loss of cognitive function. Dr. Blackwell-White also opined that Liles lost 4 IQ points "as a result of early lead toxicity." Dr. Blackwell-White relied extensively on the United States Environmental Protection Agency's Integrated Science Assessment for Lead ("EPA-ISA"). 1 She explained that the EPA-ISA found causal relationships between lead exposure and attention problems in children, as well as issues with hyperactivity and impulse control. Dr. Blackwell-White relied on other studies, chiefly one by Dr. Bruce Lanphear, ("Lanphear Study"), 2 showing a causal relationship between lead exposure in childhood and the loss of IQ points.

We shall examine the conclusions of both the EPA-ISA and the Lanphear Study in more detail infra . Dr. Blackwell-White offered her opinion, within a reasonable degree of medical certainty that, Liles "suffered brain damage as a result of his early lead exposure." She also testified that the cognitive deficits Dr. Kraft described were caused by Liles's early lead exposure. She explained that injuries suffered from lead exposure are permanent. When asked on cross-examination whether the EPA-ISA set forth a causal relationship between elevated BLLs and the specific attention deficits Dr. Kraft identified, Dr. Blackwell-White answered that the EPA-ISA speaks only to attention "generally." She concluded that the attention problems identified by Dr. Kraft fell under the umbrella term "attention" as used in the EPA-ISA.

Mark Lieberman The trial court accepted Mark Lieberman as an expert in vocational rehabilitation counseling. Lieberman explained that a vocational rehabilitation expert assesses how an individual's physical, cognitive, or psychiatric disability will affect the individual's ability to learn new skills and function in the job market. In evaluating Liles, Lieberman met with him, reviewed Dr. Kraft's report, and Liles's medical and educational records. With this information he then applied the RAPEL methodology to evaluate Liles's employment capacity.

Lieberman explained that each letter in "RAPEL" stands for a separate stage of the vocational rehabilitation analysis. We have paraphrased his description below: • R = R ehabilitation plan. This assesses the responsibilities of the rehabilitation counselor, the client time frames, and the expenses of rehabilitation. 3 • A = A ccess to labor market. What type of job can the client acquire? • P = P laceability.

Who will hire the client and why? • E = E arning capacity. How much can the client earn in his current condition and how much could they have earned prior to the disability? • L = L abor force participation. What is known about persons with the specific type of limitations that the client presents? Relying on the report from Dr. Kraft, Lieberman concluded that Liles suffered from major cognitive problems, including problems with attention.

He recognized that Liles has difficulty with auditory encoding and information processing speed. He explained that these issues "affect[ ] your ability to learn when you're sitting, listening to a lecture." He said this was "[b]ecause you [need] to hear the information, quickly process it based on other stuff you know, and put everything together to understand the new concept that's being presented." Lieberman also administered the Career Ability Placement Survey ("CAPS"), which he described as an "eight[-]part test," for "mechanical reasoning, spatial relations, verbal reasoning, ... math, ... grammar, [and] word knowledge." Liles scored below average on some aspects of the test, particularly reading and math. Although Lieberman explained that Liles had the skills of a high school graduate, he anticipated that difficulties would arise for Liles once he started college. Lieberman stated that Liles "has the IQ potential and basic academics to be ... at least an Associate['s] degree graduate." He also opined that Liles would be unable to attain that degree: It's his ability to function in the college setting as the work gets more difficult.

It's my expectation, I see [Liles] as going to college, being able to pass some classes, but eventually hitting that brick wall-the point where he's not going to be able to get the Associate['s] degree.... And what we see here is that [Liles is] going to get up to the level of an individual with a high school diploma and some college, but won't eventually reach the earnings of an individual with at least an Associate['s] degree. Michael Conte, Ph.D. Liles next offered Dr. Michael Conte as an expert in economics. Dr. Conte explained the concept of loss of earning capacity, which he described as the difference between "how much you probably would have earned absent a certain impediment or insult versus how much you're likely to earn now." To understand an individual's prospects in the labor market, Dr. Conte typically relies on an evaluation from a vocational rehabilitation expert.

Here, he relied on Lieberman's conclusions regarding Liles's likely outcomes without his disability, and his likely outcome with the disability. In addition to reviewing Lieberman's report, Dr. Conte spoke with Lieberman regarding what Liles could have accomplished without his current deficits. To reach a conclusion on earnings, Dr. Conte factored in assumptions including sex, educational attainment, and work-life expectancy. In Liles's case, Dr. Conte assumed that: Liles suffers from a cognitive disability, and ... on the basis of Lieberman's opinions, that he would not most likely have been able to compete in the labor market as an Associate's degree holder, absent the severity of his current deficits. [A]t this point in time however, he manages to proceed in the course of obtaining additional educational credits, that when he decides to enter the competitive labor market, he will most likely be able to compete at the level of a high school graduate with some college.

Dr. Conte then offered an opinion as to Liles's lost earning capacity. He described this as the difference between the career earnings of someone with the educational attainment of an Associate's degree, $3,456,127 (Liles's likely earnings without any deficits) and the career earnings of someone with the educational attainment of a high school diploma and some college, $1,757,320 (Liles's likely earnings with deficits). This difference, $1,698,808, 4 represents the sustained loss of earnings resulting from Liles's injuries. Sugarman also called expert witnesses: (1) David Nelson, MD; (2) Scott Beveridge, Ph.D.; (3) Jack Spector, MD; 5 and (4) Jerome Paige, Ph.D. 6 David Nelson, MD Dr. David Nelson was accepted as an expert in pediatrics, epidemiology, and childhood lead exposure.

Like Dr. Blackwell-White, Dr. Nelson did not examine Liles but reviewed his medical records, education records, and relied upon Dr. Kraft's neuropsychological testing. Dr. Nelson testified that, based on his review of the epidemiological literature, he would not expect a BLL of 10 mcg/dL or even 15 mcg/dL to be significant in terms of causing brain impairment. Rather, he opined that he would expect a BLL of 20 mcg/dL or above to have a significant effect. Dr. Nelson also testified that Liles's educational records did not indicate any difficulty due to cognitive impairment.

Instead, Dr. Nelson attributed Liles's educational difficulties to severe anxiety from the loss of several family members while in the fifth grade and Liles's broken thumb in high school. Dr. Nelson offered his expert opinion that, within a reasonable degree of medical certainty, Liles's lead exposure did not cause him any issues at all, that Liles does not suffer any cognitive damage from any cause, and that even if Liles had never been exposed to lead, he would not be any better off than he is today. Scott Beveridge, Ph.D. Dr. Scott Beveridge was offered as an expert in forensic vocational rehabilitation counseling. Dr. Beveridge reviewed Liles's medical records, his educational records, and the reports from Dr. Kraft, Dr. Blackwell-White, and Lieberman.

He also met with Liles just before his 18th birthday. Dr. Beveridge administered an IQ test that revealed a full-scale IQ of 96. Dr. Beveridge identified this IQ as in the "average range." Like Lieberman, Dr. Beveridge was asked to perform a vocational evaluation "to determine if there was any impact on [Liles's] ability to work and maintain employment." Dr. Beveridge employed the PEEDS-RAPEL method of analysis, a method that differs from the RAPEL method employed by Lieberman. Dr. Beveridge testified that the PEEDS-RAPEL method also accounts for parental history and educational attainment when considering the likely outcome of an evaluated individual.

Based on this evaluation, Dr. Beveridge testified that Liles has the capacity to complete an Associate's degree. Dr. Beveridge explained that Liles had expressed an interest in going into the medical field and that he could likely pursue further education in nursing after obtaining an Associate's degree. He further opined that Liles could work as a nurse throughout his normal life, and that his educational and vocational capacity was the same as it was before his lead exposure. Motions for Judgment At the conclusion of Liles's case in chief, Sugarman moved for judgment.

Sugarman argued that Liles had not proven that his elevated lead levels caused any injury, and that he had not proven the existence of any damages beyond mere speculation. Regarding causation, Sugarman pointed to Dr. Blackwell-White's testimony and argued that her opinion rested solely on epidemiological literature "without any identification of measurement for the individual to support her opinions that there has been cognitive loss caused by lead exposure." Sugarman also argued that Liles had not sufficiently proven that, but for his cognitive difficulties, he would have obtained a college degree. The trial court concluded that there was enough evidence for the issues to go to the jury and denied Sugarman's motion. At the conclusion of all the evidence, Sugarman again moved for judgment and raised the same arguments.

Once again, the trial court deemed the evidence sufficient for the jury's consideration. The jury returned a verdict for Liles in the amount of $1,302,610 ($600,000 in non-economic damages and $702,610 in economic damages). Final judgment was entered in the amount of $1,277,610 after a reduction consistent with the statutory cap on non-economic damages. Sugarman filed a timely appeal and argued that Dr. Blackwell-White did not have a sufficient factual basis for her opinions regarding causation.

Sugarman also contended that Liles had not sufficiently proven that his claimed injuries had resulted in any damages. In a reported opinion, the Court of Special Appeals affirmed the final judgment of the trial court. See Sugarman v. Liles , 234 Md. App. 442 , 172 A.3d 971 (2017). We granted Sugarman's petition for writ of certiorari to answer the following questions: 7 1.

Did Dr. Blackwell-White's causation opinion have a sufficient factual basis to establish a causal relationship between lead exposure and cognitive defects identified in Liles or his IQ loss? 2. Was there sufficient evidence for the trial court to submit the case to the jury on the issue of whether Liles's lead exposure resulted in damages? DISCUSSION Sugarman moved for judgment on two occasions, at the end of the presentation of Liles's case in chief, and at the conclusion of the evidence. The trial court denied both motions and the case was ultimately submitted to the jury.

"A judge must grant a civil defendant's motion for judgment as a matter of law if the plaintiff failed to present evidence that could persuade the jury of the elements of the tort by a preponderance of the evidence ." Darcars Motors of Silver Spring, Inc. v. Borzym , 379 Md. 249 , 270, 841 A.2d 828 (2004) (emphasis in original). See also District of Columbia v. Singleton , 425 Md. 398 , 406-07, 41 A.3d 717 (2012) ("Where the defendant, in a jury trial for negligence, argues that plaintiffs' evidence is insufficient to create a triable issue, the court determines whether an inference of negligence is permissible; that is, whether the evidence demonstrates that it is more probable than not that the defendant was negligent."). The court considers the evidence and reasonable inferences drawn from the evidence in the light most favorable to the non-moving party. Singleton , 425 Md. at 407 , 41 A.3d 717 .

We review the trial court's decision to grant or deny a motion for judgment in a civil case without deference. Id. at 406 , 41 A.3d 717 . General Causation And Attention Decrements The Court of Special Appeals held that Liles had produced sufficient evidence that his lead exposure caused injury-specifically his deficits in the areas of auditory encoding and processing speed-to survive a motion for judgment. Sugarman , 234 Md. App. at 469 , 172 A.3d 971 .

It relied on our analysis set forth in Rochkind v. Stevenson , 454 Md. at 288 -91 , 164 A.3d 254 , wherein we observed that epidemiological evidence showing a causal link between exposure and injury is usually sufficient for general causation. Liles's experts-Dr. Kraft and Dr. Blackwell-White-both testified that Liles's specific deficits were measures, or factors, of attention. Because the studies in the EPA-ISA found a causal link between lead exposure and attention decrements, the intermediate appellate court reasoned that there was no analytical gap. Sugarman , 234 Md. App. at 469 , 172 A.3d 971 .

Thus, there was a sufficient factual basis for Dr. Blackwell-White's opinion and the Circuit Court correctly determined that the weight and credibility of the parties' dueling experts was a matter for the jury to resolve. Id. Sugarman urges us to reverse the intermediate appellate court, arguing that Liles did not satisfy his burden to produce legally sufficient evidence because Dr. Blackwell-White's testimony lacked a sufficient factual basis under Md. Rule 5-702. Sugarman maintains that the opinion suffers the same analytical gap present in Rochkind because epidemiological literature does not establish a causal relationship between lead and Liles's specific deficits.

Therefore, Sugarman reasons, Dr. Blackwell-White's opinion does not permit a conclusion of general causation and is ultimately speculative. Sugarman forecasts dire consequences if we affirm the Court of Special Appeals, such as medical experts offering increasingly abstract testimony in the absence of scientific evidence or research. Liles maintains that Dr. Blackwell-White's testimony, referencing numerous medical studies in addition to the EPA-ISA, satisfied Liles's burden of proof and that the Circuit Court properly denied Sugarman's motion for judgment. Liles also points to Rochkind , emphasizing that this Court observed that the EPA-ISA identifies a causal relationship between lead exposure and "general attention deficits." Liles emphasizes that the EPA-ISA does not examine the effects of lead exposure in a "hyper-specific, granular manner[,]" but rather, the studies linking lead exposure to attention decrements use "attention" as an "umbrella term." This, Liles concludes, is a sufficient basis for Dr. Blackwell-White's testimony, and there is no analytical gap.

Maryland Rule 5-702 We first address the "sufficient factual basis" required by Md. Rule 5-702, which permits expert testimony "in the form of an opinion or otherwise," if the trial court determines "that the testimony will assist the trier of fact to understand the evidence or determine a fact in issue." Id. To make that assessment, the trial court evaluates: "(1) whether the witness is qualified as an expert by knowledge, skill, experience, training, or education[;] (2) the appropriateness of the expert testimony on that particular subject[;] and (3) whether a sufficient factual basis exists to support the expert testimony." Id. The proponent of the expert testimony carries the burden of demonstrating that these requirements are satisfied. Rochkind , 454 Md. at 286 , 164 A.3d 254 .

A "sufficient factual basis" requires both "an adequate supply of data and a reliable methodology." Id. ; see also Roy v. Dackman , 445 Md. 23 , 42-43, 124 A.3d 169 (2015). As we explained in Rochkind , "[t]o constitute 'more than mere speculation or conjecture,' the expert's opinion must be based on facts sufficient to 'indicate the use of reliable principles and methodology in support of the expert's conclusions.' " 454 Md. at 286 , 164 A.3d 254 (quoting Exxon Mobil Corp. v. Ford , 433 Md. 426 , 478, 71 A.3d 105 (2013) ). Materials relied upon by an expert need not be admissible provided that they are of the kind reasonably relied upon by experts in the particular field to form opinions or inferences on the subject. See Md. Rule 5-703(a).

To satisfy the requirement of a reliable methodology, "an expert opinion must provide a sound reasoning process for inducing its conclusion from the factual data and must have an adequate theory or rational explanation of how the factual data led to the expert's conclusion." Exxon Mobil Corp. v. Ford , 433 Md. 426 , 481, 71 A.3d 105 (2013). Expert opinions must be able to assist a trier of fact. To satisfy that requirement, the trier of fact must be able to evaluate the reasoning underlying the opinion. Ross v. Housing Auth. of Balt.

City , 430 Md. 648 , 663, 63 A.3d 1 (2013). Conclusory or ipse dixit assertions are not helpful-an expert "must be able to articulate a reliable methodology for how she reached her conclusion." Rochkind , 454 Md. at 287 , 164 A.3d 254 . Before delving into Dr. Blackwell-White's factual basis for her testimony, it is helpful to illuminate some principles of causation in cases in which an injury is alleged based on exposure to substances. Causation General causation addresses whether a particular substance can cause the kind of injury suffered by the plaintiff.

See, e.g. , id. at 291-92 , 164 A.3d 254 ; Blackwell v. Wyeth , 408 Md. 575 , 600, 971 A.2d 235 (2009). Specific causation addresses whether the substance actually caused the plaintiff's injury. See, e.g. , Aventis Pasteur, Inc. v. Skevofilax , 396 Md. 405 , 442, 914 A.2d 113 (2007) ; Wilhelm v. State Traffic Safety Comm'n , 230 Md. 91 , 99-100, 185 A.2d 715 (1962) ; see also Norris v. Baxter Healthcare Corp. , 397 F.3d 878 , 881 (10th Cir. 2005) ("General causation is whether a substance is capable of causing a particular injury or condition in the general population and specific causation is whether a substance caused a particular individual's injury."). In Ross , 430 Md. at 668 , 63 A.3d 1 , we explained a common pattern of specific causation in lead-paint exposure cases: The theory of causation ... can be conceived as a series of links: (1) the link between the defendant's property and the plaintiff's exposure to lead; (2) the link between specific exposure to lead and the elevated blood lead levels[;] and (3) the link between those blood lead levels and the injuries allegedly suffered by the plaintiff.

(footnote omitted). 8 The third link encompasses both general and specific causation-whether lead can generally cause certain injuries, and whether that exposure did cause Liles's injuries. Here, the parties' stipulations have satisfied the first and second links. Liles lived at the property owned and managed by the Petitioners and the parties stipulated that "due to Ivy Realty's negligence[,] deteriorated paint at the [Residence] substantially contributed to Mr. Liles's [BLL] ... measured by two BLLs of 11 mcg/dL and 10 mcg/dL." Thus, we concern ourselves with the third link. "[B]oth general and specific causation testimony are subject to [Md.] Rule 5-702...." Rochkind , 454 Md. at 287 n.4, 164 A.3d 254 .

If an expert's general causation opinion fails for the lack of a sufficient factual basis, and the specific causation opinion is based on the general causation opinion, then logically, the specific causation opinion also fails. Id. The first question we must resolve is whether Dr. Blackwell-White had an adequate factual basis for her testimony that lead exposure can cause attention deficits, including deficits in auditory encoding and processing speed. In Rochkind , we considered whether an expert had a sufficient factual basis to offer general causation testimony that lead exposure can cause Attention Deficit Hyperactivity Disorder ("ADHD").

Id. at 281-88 , 164 A.3d 254 . There, the plaintiff's expert, Dr. Hall-Carrington, testified that epidemiological studies collected in the EPA-ISA demonstrated that children with blood lead levels similar to those of the plaintiff could have attention problems, learning disabilities, or ADHD. Id. at 288 , 164 A.3d 254 . Dr. Hall-Carrington agreed that the EPA-ISA did not establish a causal link between ADHD and lead exposure, but that the studies listed the symptoms of ADHD.

Based on this information, she concluded that lead exposure caused the plaintiff's ADHD. Id. At the time Rochkind was decided, we had not yet determined "the extent to which epidemiological studies can support expert testimony on causation." Id. We examined other jurisdictions' precedent addressing the use of epidemiological studies, particularly General Elec.

Co. v. Joiner , 522 U.S. 136 , 118 S.Ct. 512 , 139 L.Ed.2d 508 (1997). There, the United States Supreme Court agreed with a district court that the epidemiological studies the plaintiff's experts relied on did not provide a sufficient basis to offer an opinion that exposure to polychlorinated biphenyls ("PCBs") caused lung cancer. Id. at 145-46 , 118 S.Ct. 512 . Although some of the studies the expert relied on showed statistically significant increases in lung cancer, the studies either did not refer to PCBs, or did not account for exposure to other known carcinogens.

Id. The Supreme Court explained that although experts "commonly extrapolate from existing data[,]" courts are not required to "admit opinion evidence that is connected to existing data only by the ipse dixit of the expert." Id. (italics in original). "A court may conclude that there is simply too great an analytical gap between the data and the opinion proffered." Id.

In short, the studies upon which an expert relies must provide factual support for conclusions regarding causation. Id. at 146-47 , 118 S.Ct. 512 . Applying Joiner to Rochkind , we observed that the studies in the EPA-ISA "finding a causal relationship between lead exposure and attention deficits and hyperactivity" did not support a causal relationship between lead exposure and ADHD. 454 Md. at 290 -91 , 164 A.3d 254 . Although the EPA-ISA contained studies that examined the relationship, it was one of association, rather than causation. 9 Id. at 291-92 , 164 A.3d 254 .

Thus, although there is evidence of a causal relationship between lead and some symptoms associated with ADHD, "these lead-caused behaviors do not necessarily indicate that an individual has ADHD because these behaviors are also symptoms of a variety of other learning disorders and learning disabilities." Id. at 290 , 164 A.3d 254 . Indeed, the EPA-ISA cautioned that research showing an association between lead exposure and ADHD had been critiqued for failing to account for potential confounding 10 factors such as familial history, parenting, and socio-economic status. Id. at 292 , 164 A.3d 254 . Thus, Dr. Hall-Carrington's testimony suffered from an analytical gap because it "overstated the known effects of lead exposure." Id. at 291 , 164 A.3d 254 .

Her testimony was not admissible under Md. Rule 5-702 because it lacked "epidemiological studies-or other reliable evidence-demonstrating a causal link between lead exposure and ADHD ...." Id. at 294 , 164 A.3d 254 . Even if an expert believes wholeheartedly that the link exists, that opinion requires a scientific basis. Without it, that opinion is ipse dixit . Id.

(citing Palmer v. Asarco, Inc. , 510 F.Supp.2d 519 , 531 (N.D. Okla. 2007) ). Mindful of our recent decision in Rochkind and its discussion of the "analytical gap," we next examine the basis for Dr. Blackwell-White's opinion. We begin with a discussion of some principles of epidemiology, as well as an explanation of the EPA-ISA's methodology and findings. Epidemiology And The EPA-ISA "Epidemiology is the field of public health and medicine that studies the incidence, distribution, and etiology of disease in human populations." Michael D. Green, Michal Freedman & Leon Gordis, Reference Guide on Epidemiology , in Reference Manual on Scientific Evidence 549, 551 (3d ed. 2011).

Epidemiological research can lend support to the question of general causation. Id. at 552 . Such studies have been used routinely in litigation. "Where the study properly accounts for potential confounding factors and concludes that exposure to the agent is what increases the probability of contracting the disease, the study has demonstrated general causation-that exposure to the agent 'is capable of causing the illness in the general population.' " In re Silicone Gel Breast Implants Prods.

Liab. Litig. , 318 F.Supp.2d 879 , 893 (C.D. Cal. 2004) (emphasis in original) (quoting In re Hanford Nuclear Reservation Litig. , 292 F.3d 1124 , 1134 (9th Cir. 2002) ); see also Norris , 397 F.3d at 882 ; Henricksen v. ConocoPhillips Co. , 605 F.Supp.2d 1142 , 1158 (E.D. Wash. 2009) ; Green et al., supra , at 551-52 & n.2. The primary basis for much of Dr. Blackwell-White's testimony was the EPA-ISA. It is necessary to first explain precisely what the EPA-ISA is.

It is an integrated science assessment that reviewed, synthesized, and evaluated other scientific studies and research. U.S. Envtl. Protection Agency, Integrated Science Assessment for Lead, EPA/600/R-10/075F, at xliv (June 2013), https://perma.cc/5ZRA-W54H. It included peer-reviewed studies, reviewed reports, and EPA analyses using publicly available data.

Id. at xlv. Studies were selected "based on the general scientific quality of the study, and consideration of the extent to which the study is informative and policy relevant." Id. at xlvi. The EPA-ISA scrutinized the evidence, received peer input, and ultimately evaluated the weight of that evidence to reach conclusions about causal determinations or the lack thereof. Id. at 1, Fig.

III

"Cause" is defined as "an agent that brings about an effect or result." Id. at li. "Association" is "the statistical relationship among variables; alone, however, it is insufficient proof of a causal relationship between an exposure and a health outcome." Id. Epidemiological studies primarily assess whether associations exist, as well as their relative strength, between an agent and a disease. Berry v. CSX Transp., Inc. , 709 So.2d 552 , 567 (Fla.

Dist. Ct. App. 1998). Epidemiologists may or may not infer that causal relationships exist from studies demonstrating associations. Id. at 567-68 .

Finding causation from associations also requires identifying and controlling for potential confounding factors to rule out alternative explanations for an association. EPA-ISA, supra , at liv-lv. See also King v. Burlington N. Santa Fe Ry. Co. , 277 Neb. 203 , 762 N.W.2d 24 , 35-36 (2009).

To synthesize studies demonstrating associations, the EPA-ISA applied a variant of the Hill Factors, 11 a generally accepted method used in epidemiology, 12 to determine causation. These factors include: • Consistency of the observed association; 13 • Coherence; 14 • Biological plausibility; 15 • Biological gradient (exposure-response relationship); 16 • Strength of the observed association; 17 • Experimental evidence; 18 • Temporal relationship of the observed association; 19 • Specificity of the observed association; 20 and • Analogy. 21 Id. at lix. When the EPA-ISA reaches a conclusion about a causal determination for a particular health effect from exposure to an agent, it means that: Evidence is sufficient to conclude that there is a causal relationship with relevant pollutant exposures (i.e., doses or exposures generally within one to two orders of magnitude of current levels). That is, the pollutant has been shown to result in health effects in studies in which chance, bias, and confounding could be ruled out with reasonable confidence .

For example: a) controlled human exposure studies that demonstrate consistent effects; or b) observational studies that cannot be explained by plausible alternatives or are supported by other lines of evidence (e.g., animal studies or mode of action information). Evidence includes multiple high-quality studies. Id. at lxii (emphasis added). 22 In short, the EPA-ISA used a widely accepted method to reach conclusions about causation, and neither party has questioned the accuracy of those conclusions. The EPA-ISA examined studies addressing the effects of lead exposure on "externalizing behaviors such as attention, impulsivity, hyperactivity, destructive behavior, and truancy[,]" which, it observed, had not been examined as extensively as the effect of lead on cognitive function.

Id. at 4-150. It identified three "major domains of externalizing behavior disorders," which include attention deficits. Id. The EPA-ISA was careful to emphasize that clinically diagnosed disorders like ADHD are "considered to have a strong familial component," and studies reporting associations between BLLs and ADHD must account for confounding factors.

Id. at 4-151. "Within the attention deficit hyperactivity disorder domain of externalizing behaviors, studies of Pb [ 23 ] exposure have focused primarily on attention, impulsivity, and hyperactivity." Id. at 4-153. The EPA-ISA examined the evidence for each outcome individually. Id.

Of most relevance to this case is the survey of studies of attention in children. The EPA-ISA defined attention as "the ability to maintain a consistent focus on an activity or relevant stimuli and can be assessed by examining sustained attention, concentration[,] or distractibility." Id. It then reviewed the studies that found associations between blood lead levels and attention decrements. Id. at 4-153-54.

While some studies included examinations of attention and hyperactivity, others focused solely on attention. See id. at 4-156-63. In summarizing its findings, the EPA-ISA evaluated attention, impulsivity, and hyperactivity together because they fell within the same relevant domain of externalizing behaviors. Id. at 4-289.

The EPA-ISA found a "causal relationship between Pb exposure and attention decrements, impulsivity, and hyperactivity in children" that was "supported by multiple lines of evidence ...." Id. This relationship was "further supported by the consideration for several potential confounding factors in prospective studies." Id. at 4-291. These findings were based on the consistency of the available evidence, biological plausibility, and underlying modes of action. Id. at 4-294.

Although the EPA-ISA evaluated the evidence relating to these effects collectively, it does not set forth clinical criteria for assessing whether a particular individual has been affected by lead. The EPA-ISA examined studies concerning attention, impulsivity, and hyperactivity to reach conclusions about causation due to lead exposure. But the EPA-ISA's conclusion that lead can cause these three externalizing effects does not mean that the absence of one or two of these effects necessarily leads to the conclusion that general causation fails. After all, some of the studies discussed in the EPA-ISA focused exclusively on attention, and the EPA-ISA examined attention separately from the other effects. 24 The EPA-ISA is an integrated assessment that broadly examined various health outcomes present in multiple studies to reach a generalized conclusion about the causal relationship between lead exposure and attention decrements.

Sugarman is correct that the EPA-ISA does not specifically identify types of attention decrements found nor does it mention processing speed or auditory encoding. But Sugarman ignores Dr. Blackwell-White's medical expertise with respect to attention deficits. The question we must resolve is whether Dr. Blackwell-White had a sufficient factual basis to opine that auditory encoding and processing speed are within the realm of attention decrements caused by lead contemplated in the EPA-ISA, or whether her testimony suffered from the same analytical gap present in Rochkind . The Analytical Gap As we explained in Savage v. State , 455 Md. 138 , 163, 166 A.3d 183 (2017), the "hallmark" of the analytical gap is "the failure by the expert witness to bridge the gap between his or her opinion and the empirical foundation on which the opinion was derived." In Rochkind , we concluded that an analytical gap existed because the EPA-ISA, which supplied the factual basis for Dr. Hall-Carrington's opinion testimony, although finding a causal relationship between lead exposure and attention deficits and hyperactivity, did not go so far as to conclude that lead exposure caused ADHD. 454 Md. at 290 , 164 A.3d 254 .

We had discussed the analytical gap even before Rochkind in Blackwell , 408 Md. at 606 -08 , 971 A.2d 235 . There, we concluded that an expert's opinion did not bridge the gap because, although the data he used was reliable, the expert's extrapolation from that data was defective. The basis of his opinion, including causation and methodology, were not generally accepted as reliable in the expert's particular scientific field. Id. at 608-10 , 971 A.2d 235 .

Similarly, in Giant Food, Inc. v. Booker , 152 Md. App. 166 , 178, 831 A.2d 481 (2003), the Court of Special Appeals considered whether a plaintiff presented sufficient evidence that exposure to Freon caused his asthma. The plaintiff's expert in pulmonary medicine offered an opinion on causation. Id. at 185 , 831 A.2d 481 . The basis for the opinion was an examination of the plaintiff, his medical history dating from the accident, and documented exposure to Freon.

Id. at 184-87 , 831 A.2d 481 . The Court concluded that the expert lacked a sufficient factual basis under Md. Rule 5-702 and that his methodology was "woefully inadequate" because the expert did not identify any literature supporting the causation theory. Id. at 189 , 831 A.2d 481 . Cases from other jurisdictions provide further examples of an analytical gap.

See, e.g. , Bland v. Verizon Wireless, LLC , 538 F.3d 893 , 897-98 (8th Cir. 2008) (analytical gap existed because expert lacked data about level of exposure to Freon that risks asthma as well as degree and concentration of exposure); Ruggiero v. Warner-Lambert Co. , 424 F.3d 249 , 253-55 (2d Cir. 2005) (no basis for expert opinion on causation because of inadequate support from research and the differential diagnosis did not bolster general causation opinion); United States v. Mamah , 332 F.3d 475 , 478 (7th Cir. 2003) (expert testimony defective because of absence of empirical link between research and opinion); Mitchell v. Gencorp, Inc. , 165 F.3d 778 , 779 (10th Cir. 1999) (analytical gap existed where expert witnesses provided no scientific evidence setting forth causal link between chemicals and the plaintiff's specific type of leukemia ); Rockman v. Union Carbide Corp. , 266 F.Supp.3d 839 , 847 (D. Md. 2017) (experts "conflated data on pleural mesothelioma and amphibole asbestos with data on peritoneal mesothelioma and chrysotile asbestos") (emphasis in original); see also Goeb v. Tharaldson , 615 N.W.2d 800 , 816 (Minn. 2000) (expert made significant leap in causation opinion because he did not review pre- or post-exposure medical records, relied only on self-reported information, and applied his own tests not in use or subject to peer review). On the other hand, King , 762 N.W.2d at 44 , illustrates how an expert who relies on peer-reviewed medical literature can "appropriately support a general causation opinion" without falling into the analytical gap. There, the expert cited to evidence including "human data studies, animal studies, and toxicology studies[ ]" to support his conclusion that exposure to diesel exhaust can cause a certain type of cancer. Id. at 49 .

The expert was required to "consult the relevant scientific literature and draw a conclusion." Id. His testimony, although imperfect, did not require studies showing definite conclusions of a causal relationship because the expert was qualified to interpret and extrapolate from the relevant studies. Id. To bridge the analytical gap, an expert's testimony must have a sufficient factual foundation.

Savage , 455 Md. at 163 , 166 A.3d 183 ; Rochkind , 454 Md. at 294 , 164 A.3d 254 ; Blackwell , 408 Md. at 606 -08 , 971 A.2d 235 ; Joiner , 522 U.S. at 146 , 118 S.Ct. 512 . It is permissible for an expert to reasonably extrapolate from existing data provided that a sufficient factual basis for that opinion exists. But when the only connection between opinion testimony and the data is the expert's assertion, without more, such testimony cannot support general causation. Rochkind , 454 Md. at 293 -94 , 164 A.3d 254 .

Dr. Blackwell-White was permitted to extrapolate from the data in offering her opinion regarding causation, provided a sufficient foundation of fact existed. Sugarman contends that the core failing in Dr. Blackwell-White's opinion, and hence, her failure to bridge the analytical gap, was her assessment that auditory encoding and processing speed are within the realm of attention decrements identified in the EPA-ISA. [ Defense Counsel ]: ... [A]re you able to say that the attention association the EPA is speaking of is the same as the very specific attention that Dr. Kraft is referring to when he specifies, I believe, auditory encoding and processing speed? [ Dr. Blackwell-White ]: Not only the EPA, but a good much of the lead literature involving children speaks to attention. They don't parse it out as to what kind of attention. They are using the umbrella term "attention." And so it is my opinion that the deficits that Dr. Kraft found are part of that umbrella term "attention." Dr. Blackwell-White testified that the EPA-ISA and other research on the effects of lead exposure found a causal relationship between lead and various problems in children, including attention, impulsivity, and hyperactivity.

She explained that problems with attention were "one of the earliest effects that lead was thought to have on children." She also described the way lead affects brain development by disrupting neurotransmission, which she testified could affect attention. Both Dr. Kraft and Dr. Blackwell-White testified that deficits in auditory encoding and processing speed are "factors of attention." They also described how those deficits were related to attention. Although the literature does not mention these particular deficits, both experts testified that they were within the realm of general attention deficits, and the literature does state that general attention deficits can result from lead exposure. 25 See Rochkind , 454 Md. at 290 -91 , 164 A.3d 254 . Rochkind is distinct from this case.

There, the expert lacked "epidemiological studies-or other reliable evidence-demonstrating a causal link between lead exposure and ADHD" but nonetheless offered a causation opinion. Id. at 294 , 164 A.3d 254 . A causal relationship between lead exposure and some symptoms of ADHD did not warrant testimony linking the two. The symptoms, we observed, were present in a "variety of other disorders and learning disabilities." Id. at 290 , 164 A.3d 254 .

ADHD, however, has precise diagnostic criteria and requires ruling out other behavioral disorders. Id. at 291 , 164 A.3d 254 . Further, the EPA-ISA emphasized other potential confounding factors that undermined Dr. Hall-Carrington's opinion. Id. at 292 , 164 A.3d 254 .

The EPA-ISA could not support her opinion because the studies discussed therein "only reveal an association between lead exposure and ADHD." Id. at 291 , 164 A.3d 254 (emphasis in original). Her opinion lacked an adequate factual basis because the source did not logically support her conclusion. Id. at 294-95 , 164 A.3d 254 . Here, by contrast, the EPA-ISA identified a causal relationship between attention decrements and exposure to lead.

Unlike in Rochkind , none of the experts opined that Liles has a diagnosable learning disability or behavioral disorder. Dr. Blackwell-White explained lead's impact on a developing brain, including the way it affects attention. She offered the opinion that Liles suffered from the kind of generalized attention deficits the EPA-ISA identified as being caused by lead exposure. Because Dr. Blackwell-White's opinion testimony does not suffer the same defects as were present in Rochkind , we hold that she had a sufficient factual basis to offer an opinion regarding general causation.

We next address Sugarman's challenge to Dr. Blackwell-White's specific causation testimony that, as a result of his elevated BLLs, Liles lost 4 IQ points. Specific Causation And IQ Loss The Court of Special Appeals concluded that Maryland cases have accepted the Lanphear Study as a "basis for calculating IQ loss for plaintiffs in lead paint cases." Sugarman , 234 Md. App. at 469 , 172 A.3d 971 (citing Levitas v. Christian , 454 Md. 233 , 247-48, 164 A.3d 228 (2017) ; Rochkind v. Stevenson , 229 Md. App. 422 , 469, 145 A.3d 570 (2016), rev'd on other grounds , 454 Md. 277 , 164 A.3d 254 (2017) ). The Court reasoned that Dr. Blackwell-White had a sufficient factual basis because she based her opinion regarding Liles's IQ loss on the Lanphear Study. Id. at 470, 145 A.3d 570 .

Her testimony, the intermediate appellate court said, satisfied Liles's "burden of providing evidence, which the jury could accept or reject, that Mr. Liles's lead exposure caused cognitive damage." Id. Sugarman does not question that epidemiological data has found a causal relationship between lead exposure and IQ loss in population studies. Thus, general causation-that the agent can cause the kind of injury the plaintiff suffers from-is met. See Norris , 397 F.3d at 991 .

Rather, Sugarman insists that specific causation is lacking-namely, there is insufficient evidence to find that Liles's exposure to lead actually caused a loss of 4 IQ points. See id. Sugarman asserts that "there is no question whether or how the expert can reliably use the Lanphear Study to quantify loss once it is determined that IQ loss did occur." Thus, Sugarman reasons, an expert may use the Lanphear Study methodology to calculate IQ loss, provided that there is expert evidence that can prove the loss. Here, Sugarman maintains, Dr. Blackwell-White's testimony was not sufficient because she assumed IQ loss without determining whether an injury occurred.

Liles disagrees, maintaining that Dr. Blackwell-White had a "sound basis in the medical literature"-the EPA-ISA and the Lanphear Study-to offer an opinion that Liles lost IQ points. He claims that Sugarman advances a "novel[ ] and unsubstantiated" argument-that a "plaintiff must first prove that he sustained an IQ loss before the Lanphear Study can be utilized to calculate that loss." Liles maintains that he has shown an injury-"cognitive deficits and IQ loss[.]" He avers that merely because his IQ is in the average range does not mean that he has not lost IQ points due to lead exposure. The Lanphear Study is a pooled analysis that examined the relationship between children's performance on IQ tests and BLLs less than 10 mcg/dL in multiple cohort studies around the world. See Bruce P. Lanphear et al., Low-Level Environmental Lead Exposure and Children's Intellectual Function: An International Pooled Analysis , 113(7) Envtl.

Health Persps. 894, 894-95 (July 2005). It found that "children with certain average lifetime blood levels lost a specific number of IQ points." Levitas v. Christian , 454 Md. 233 , 240, 164 A.3d 228 (2017) ; see also Lanphear, supra , at 896-97. Cases from this Court, as well as the Court of Special Appeals, have addressed the use of epidemiological studies, as well as the Lanphear Study, in expert medical testimony about a lead-exposed plaintiff's IQ loss. The parties dispute how this precedent applies.

Maryland Cases Addressing IQ Loss In Lead Cases Sugarman contends