Argued: February 6, 2017
Barbera, C.J. Greene Adkins McDonald Watts Getty Battaglia,
Lynne A. (Senior Judge, Specially Assigned), JJ.
about an expert's qualifications and foundation for his
opinion are no strangers to appellate courts, and the complex
issues of causation in lead paint cases generally require
expert testimony, which is often challenged. Today we review
a case in which the trial court excluded the plaintiff's
expert witness-a ruling fatal to his claim. We consider
whether it erred in doing so.
AND LEGAL PROCEEDINGS
Michael Christian was born on February 12, 1990. From his
birth until October 1992, he resided with his mother,
Nickolas Skinner ("Nickolas"), and grandmother,
Betty Skinner ("Betty"),  at 3605 Spaulding Avenue
("Spaulding") in Baltimore City. Christian and his
mother then moved to 4946 Denmore Avenue
("Denmore") in October 1992, where they resided for
almost a year. In September 1993, Christian and his mother
moved back to Spaulding and lived there for another four
years, until September 1997.
blood was tested eight times between November 1990 and
October 1993. In April 1991, he exhibited an elevated free
erythrocyte protoporphyrin ("FEP") level, which
does not measure a child's blood lead level but is an
initial screening test for lead exposure. From February 1992
to October 1993, Christian displayed elevated blood lead
levels five times as follows:
Blood Lead Level 
Christian's Address 
February 20, 1992
February 18, 1993
July 16, 1993
September 2, 1993
October 6, 1993
2011, Christian filed suit in the Circuit Court for Baltimore
City against Petitioner Stewart Levitas, the owner of
Spaulding when he lived there, alleging negligence and
violations of the Maryland Consumer Protection
In February 2012, Arc Environmental, Inc. ("Arc")
tested the interior and exterior of Spaulding for lead using
x- ray fluorescence testing. Arc summarized its findings in a
report for Christian ("Arc Report"). Thirty-one
interior surfaces and five exterior surfaces tested positive
for lead. The lead-positive interior surfaces included door
jambs, baseboards, and window sills, casings, and sashes.
Exterior window sashes, casings, and door jambs also tested
positive for lead.
discovery, Christian designated Howard Klein, M.D., a
pediatrician with experience treating lead-poisoned children,
as an expert witness who would opine on the source of
Christian's lead exposure-source causation-and his
lead-caused injuries- medical causation. As to the source of
Christian's lead exposure, Dr. Klein testified in his
deposition that he was "of the opinion that [Christian]
was exposed to lead-based paint" at Spaulding. The basis
for his opinion was: (1) the age of Spaulding-built in 1944;
(2) the Arc Report; (3) a Maryland Department of the
Environment ("MDE") certification reflecting that
the property was not lead free; (4) a Department of Housing
and Community Development ("DHCD") violation that
detailed the poor condition of the property; (5)
Christian's elevated FEP and blood lead levels while he
was living at Spaulding and Denmore; (6) Betty's and
Nickolas's deposition testimony that Spaulding was in
disrepair while Christian lived there; (7) Nickolas's
testimony that she saw Christian touch areas where paint was
peeling around the windowsills at Spaulding; and (8)
Nickolas's testimony that Christian stayed at Spaulding
under the supervision of family members while she was at work
during the day, both while they were living at Spaulding and
while they were living at Denmore. Dr. Klein further
testified that these facts establish that "there was
lead-based paint [at Spaulding]." Finally, he
acknowledged that Denmore was also a source of
Christian's lead exposure.
expert report on medical causation, Dr. Klein concluded
"within [a] reasonable degree of medical certainty"
that lead caused Christian's mental retardation, impaired
cognition, and learning disabilities. He further opined in
his deposition that as a result of Christian's exposure
to lead, he lost 7.4 to 9.4 IQ points. Dr. Klein based his
opinion on: (1) a neuropsychological evaluation of Christian
by Barry Hurwitz, Ph.D.; (2) Christian's medical records;
(3) Christian's Answers to Interrogatories; (4)
information on Spaulding and Denmore; (5) Christian's
Maryland Department of Health and Mental Hygiene
("DHMH") lead testing records; (6) MDE records; (7)
DHCD records; and (8) Christian's school records. To
calculate Christian's IQ loss, he relied on the Lanphear
study,  which found that children with certain
average lifetime blood lead levels lost a specific number of
IQ points. Dr. Klein averaged Christian's blood lead
levels and then determined his loss in IQ points based on the
filed a motion to exclude Dr. Klein from testifying about
source causation on the grounds that he lacked both the
necessary qualifications and a sufficient factual basis for
his opinion. Levitas also moved for summary judgment in
his favor if Dr. Klein were excluded.
10, 2013, the Circuit Court held a hearing on Levitas's
motion to exclude Dr. Klein. At the hearing, Levitas argued
that Dr. Klein should be precluded from testifying about both
source causation and medical causation. Ruling from the
bench, the hearing judge excluded Dr. Klein's testimony
on both of these topics. The court reasoned that Dr. Klein
should be prevented from testifying about the source of
Christian's lead exposure because "he did not, or
had very little . . . information concerning other sources
[of lead exposure]." It also precluded Dr. Klein from
testifying about the cause and extent of Christian's
injuries because he was not qualified and his opinion lacked
a sufficient factual basis under Maryland Rule 5-702. As to
his qualifications, the court reasoned that Dr. Klein would
not be able to explain the IQ test results to the jury
because he does not use the test in his own practice. As to
his factual basis, the court explained that Dr. Klein relied
on information from Dr. Hurwitz and Christian's attorney
in developing his opinion, rather than examining Christian
himself, which was not sufficient. The Circuit Court declined
to grant Levitas's motion for summary judgment, however,
because the Arc Report was "direct evidence" of
lead at Spaulding.
August 20, 2013, the Circuit Court entered a written order
precluding Dr. Klein from offering expert opinions on
"source, IQ loss, alleged injuries due to lead, or other
causation issues." For the purposes of appealing the
Circuit Court's decision to exclude Dr. Klein, the
parties agreed that without Dr. Klein's testimony,
Christian could not make out a prima facie case of negligence
because he could not establish medical causation. Therefore,
the parties requested that the Circuit Court enter summary
judgment in Levitas's favor to allow Christian to appeal
the expert's exclusion. The court granted the request,
and Christian appealed.
first of two Court of Special Appeals opinions, the
intermediate appellate court affirmed the Circuit Court's
decision to exclude Dr. Klein. Christian appealed to this
Court, and we, in a per curiam order, vacated the judgment
and remanded the case for reconsideration in light of Roy
v. Dackman, 445 Md. 23 (2015), reconsideration
granted, (Nov. 24, 2015). Christian v. Levitas,
445 Md. 240 (2015). On remand, the Court of Special Appeals,
in an unreported opinion, reversed the Circuit Court's
decision to exclude Dr. Klein. Christian v. Levitas,
2016 WL 4076100, at *6 (Md. Ct. Spec. App. Aug. 1, 2016). It
concluded that Dr. Klein was qualified and had a sufficient
factual basis to opine that Christian was exposed to lead at
Spaulding and that lead caused his injuries. Id. at
*4- *5. Levitas appealed.
granted certiorari to answer the following
1. Did the trial court err in excluding Dr. Klein's
testimony regarding lead-source causation?
2. Did the trial court err in excluding Dr. Klein's
testimony regarding medical causation? Because we answer
these questions in the affirmative, we shall affirm the
judgment of the Court of Special Appeals.
often said that decisions to admit or exclude expert
testimony fall squarely within the discretion of the trial
court. See, e.g., Bryant v. State, 393 Md.
196, 203 (2006) (collecting cases). A discretionary ruling,
however, is not boundless and must be tethered to reason. We
have explained that an abuse of discretion is
"discretion manifestly unreasonable, or exercised on
untenable grounds, or for untenable reasons."
Neustadter v. Holy Cross Hosp. of Silver Spring,
Inc., 418 Md. 231, 241 (2011) (emphasis added) (quoting
Touzeau v. Deffinbaugh, 394 Md. 654, 669 (2006)).
Appellate courts will not affirm a trial court's
discretionary rulings "when the judge has resolved the
issue on unreasonable or untenable
grounds." Id. (internal quotation marks
omitted). Such grounds include "when a trial judge
exercises discretion in an arbitrary or capricious manner or
when he or she acts beyond the letter or reason of the
law." Garg v. Garg, 393 Md. 225, 238 (2006)
(citation omitted). The trial court must apply the correct
legal standard and "a failure to consider the proper
legal standard in reaching a decision constitutes an abuse of
discretion." Neustadter, 418 Md. at 242
we examine the Circuit Court's rationale for excluding a
crucial expert witness to assess whether it abused its
contends that the Circuit Court correctly excluded most of
Dr. Klein's testimony because he lacked a sufficient
factual basis to opine about the source of Christian's
lead exposure and the nature and extent his injuries related
to such exposure.Christian flatly disagrees.
testimony is meant to assist the jury in resolving an issue
outside the average person's realm of knowledge.
Roy, 445 Md. at 41 (citing Radman v.
Harold, 279 Md. 167, 169 (1977)). Under Maryland Rule
5-702, expert testimony "may be admitted, in the form of
an opinion or otherwise, if the court determines that the
testimony will assist the trier of fact to understand the
evidence or to determine a fact in issue." The court
bases this determination on three factors: "(1) whether
the witness is qualified as an expert by knowledge, skill,
experience, training, or education[;] (2) the appropriateness
of the expert testimony on the particular subject[;] and (3)
whether a sufficient factual basis exists to support the
expert testimony." Md. Rule 5-702.
repeatedly explained that an expert may be qualified to
testify if he "is reasonably familiar with the subject
under investigation." Roy, 455 Md. at 41
(emphasis added) (quoting Radman, 279 Md. at 169).
This familiarity can come from "professional training,
observation, actual experience, or any combination of these
factors." Radman, 279 Md. at 169. An expert,
therefore, does not need to have hands-on experience with the
subject about which he proposes to testify. Id. at
170-71 (citations omitted). The often-cited illustration of
this concept is a law professor who is an expert in trial
procedure even though she has never tried a case.
Id. at 171 (citation omitted). Similarly, a doctor
may be qualified to testify as a medical expert even though
she does not have experience with a particular procedure or
area of specialization. Id.
expert's testimony is admitted "because it is based
on his special knowledge derived not only from his own
experience, but also from the experiments and reasoning of
others, communicated by personal association or through books
or other sources." Id. at 170 (citation
omitted). "It is sufficient if the court is satisfied
that the expert has in some way gained such experience in the
matter as would entitle his evidence to credit."
Id. at 169 (citation omitted). A trial court may not
exclude an expert if "his reading can be assumed to
constitute part of his general knowledge adequate to enable
him to form a reasonable opinion of his own."
Id. at 170 (citation omitted).
testimony must also have an adequate factual basis so that it
is "more than mere speculation or conjecture."
Exxon Mobil Corp. v. Ford, 433 Md. 426, 478, as
supplemented on denial of reconsideration, 433 Md. 493
(2013) (citation omitted). If an expert's conclusions are
not supported by an adequate factual basis, his opinion has
no probative force. Beatty v. Trailmaster Prod.,
Inc., 330 Md. 726, 741 (1993) (citation omitted). The
probative value of an expert's testimony is directly
related to the "soundness of [the] reasons given"
for his conclusions. Id. (citation omitted). An
adequate factual basis requires: (1) an adequate supply of
data; and (2) a reliable methodology for analyzing the data.
Roy, 445 Md. at 42-43 (citation omitted);
Ford, 433 Md. at 478 (citation omitted). In
addition, if the facts and data that an expert relies on are
"of a type reasonably relied upon by experts in the
particular field in forming opinions or inferences upon the
subject, " they need not be independently admissible at
trial. Md. Rule 5-703(a).
assessing the expert-witness factors, the trial court is only
concerned with whether the expert's testimony is
admissible. "[O]bjections attacking an expert's
training, expertise or basis of knowledge go to the weight of
the evidence and not its admissibility." Baltimore
Gas & Elec. Co. v. Flippo, 112 Md.App. 75, 98
(1996), aff'd, 348 Md. 680 (1998) (citation
omitted). An expert's qualifications and methods may be
teased out during cross-examination, and the jury can then
assess how much weight to give his testimony. Roy,
445 Md. at 43. "Even if a witness is qualified as an
expert, the fact finder need not accept the expert's
opinion." Walker v. Grow, 170 Md.App. 255, 275
third factor in Rule 5-702-"sufficient factual
basis"-garners the most debate between the parties. The
Circuit Court restricted Dr. Klein's testimony on the
ground that he did not have a "substantial factual
basis" for his opinion that lead inside Spaulding caused
Christian's elevated blood lead levels because he lacked
"information concerning other possible sources."
Levitas asks us to affirm this ruling. Relying on Ross v.
Housing Authority of Baltimore City, 430 Md. 648 (2013),
Levitas argues that Dr. Klein could not conclude that
Spaulding was a source of Christian's lead exposure
because he did not consider other properties or conduct an
independent investigation. We are not persuaded.
lends scant support to Levitas-markedly more facts underlie
Dr. Klein's opinion than were present in that case. In
Ross, lead testing was conducted on the subject
property, but the testing only detected lead-based paint on
the exterior and one interior surface. Ross, 430 Md.
at 654-55. The testimony of the expert, Pamela
Blackwell-White, M.D., was quite equivocal-saying that if
there was any lead-based paint in a property, she assumed it
was the most probable source of lead exposure "until
proven otherwise, " especially if it was built before
1970. Id. at 660. Importantly, she
testified that "she was merely identifying
'potential risk' and could not make any statement as
to causation with certainty." Id. at 664. We
concluded that she lacked an adequate factual basis to opine
that the subject property was the source of the
plaintiff's lead exposure. Id. at 663. We
reasoned that because Dr. Blackwell-White could not explain
how she weighed certain pieces of information in reaching her
conclusion, her opinion would confuse rather than assist the
trier of fact. Id.
contrast, Dr. Klein concluded-with a reasonable degree of
medical certainty- that Spaulding was a reasonably probable
source of Christian's lead exposure for several reasons:
• The 2012 Arc Report found that 31 interior locations
and five exterior locations tested positive for lead;
• Lead paint was banned federally in 1978, and therefore
it was unlikely that Spaulding had been painted with
lead-based paint since Christian lived there in the 1990s;
• DHCD records described the poor condition of the
property; • An MDE certification indicated
that Spaulding was not lead free;
• Christian's FEP and blood lead levels were first
found to be elevated while he was living at Spaulding, when
he had not yet lived anywhere else;
• Family members testified that Spaulding was in a
deteriorated condition while Christian was living there and
that Christian touched peeling paint at the property; and
• Christian regularly stayed at Spaulding during the day
while his mother was at work, both when he lived there and
when he lived at Denmore.
Klein acknowledged that Denmore was also a source of
Christian's lead exposure. Thus, unlike the expert in
Ross, he did not jump to the conclusion that
Spaulding was a source merely because it contained lead
paint. Spaulding's lead testing was one of
multiple facts that Dr. Klein considered when developing his
Dissent claims that expert witnesses in lead paint cases must
exclude other properties to opine that a particular property
was a substantial contributing factor to the plaintiff's
injuries. Dissent Slip Op. at 22-23. It also contends that
the plaintiff must establish that "the subject property
was a more probable source" of his injuries than other
possible sources. Id. at 5. Both of these assertions
stem from a fundamental misunderstanding of the substantial
factor test. The substantial factor test applies when
"two or more independent negligent acts bring about an
injury." Pittway Corp. v. Collins, 409 Md. 218,
244 (2009). Under the test, an actor's conduct is a
cause-in-fact of the plaintiff's injuries when it is
"a substantial factor in bringing about the harm."
Id. (quoting Restatement (Second) of Torts §
431 (Am. Law Inst. 1965)). The substantial factor test does
not require experts to exclude other properties as possible
contributing sources or the plaintiff to show that one cause
had a greater impact than any other substantial factor
causing the harm. See Eagle-Picher Indus., Inc.
v. Balbos, 326 Md. 179, 209 (1992). It would be
illogical for us to require an expert to narrow the
plaintiff's lead exposure down to a single source when
the substantial factor test, by its very definition, permits
more than one cause of injury.
discretion accorded to trial judges in evidentiary rulings
calls for an exercise of judgment using applicable legal
standards. Neustadter, 418 Md. at 241-42. Here, the
trial court excluded Dr. Klein's proffered testimony
about source causation because he had "very little . . .
information concerning other sources [of lead
exposure]." In doing so, it thus relied on a purported
rule of law that an expert must exclude other properties
before he can testify that the plaintiff was exposed to lead
at the subject property. But, as discussed supra,
this is not the rule. Moreover, in Hamilton v.
Kirson, 439 Md. 501 (2014), we dismissed concerns over
the experts being "provided with little information on
other potential sources of lead exposure." Id.
at 544. We explained, "[T]here may be other ways that an
injured plaintiff may establish that it was probable that the
interior of a subject house contained lead" besides
eliminating other possible sources of lead exposure.
Id. We have only required that an expert be able to
adequately explain how he determined that a property was a
source of the plaintiff's lead exposure so that the trier
of fact can evaluate his reasoning. Ross, 430 Md. at
663-64 (citation omitted). By relying on the wrong legal
standard, the trial court abused its discretion.
first factor of Rule 5-702-qualification by knowledge, skill,
experience, training, or education-comes into play as we
consider the Circuit Court's exclusion of Dr. Klein's
testimony about the cause of Christian's injuries.
Although the parties dispute the exact grounds for this
ruling, our examination of the record reveals that the
Circuit Court precluded Dr. Klein from testifying about
Christian's injuries ...