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DISTRICT OF COLUMBIA COURT OF APPEALS

No. 13-CV-1177

CRAIG L. RUSSELL, APPELLANT,

V.

CALL/D, LLC, APPELLEE. 

Appeal from the Superior Court

of the District of Columbia

(CAB-5151-12)

(Hon. Natalia Combs Greene, Motions Judge)

(Argued October 21, 2014 Decided April 15. 2016)

Peter T. Enslein, with whom Kenneth D. Bynum was on the brief, for 

appellant.

Susan E. Smith, with whom Thomas P. Bernier, was on the brief, for 

appellee. 

Before FISHER, THOMPSON, and EASTERLY, Associate Judges.

THOMPSON, Associate Judge: In June 2012, appellant Craig Russell brought 

a lawsuit asserting ―negligence – premises liability‖ and ―strict liability/negligent 

failure to warn‖ claims against appellee Call/D, LLC (―Call/D‖), the owner of the 

apartment building where appellant was residing when he began to suffer the 

symptoms of Legionnaires‘ disease, with which he was diagnosed in May 2011. 
2

Russell alleged in his Complaint and subsequent deposition that sewage back-ups 

in the apartment building and sewage-contaminated water that was allowed to 

stand in a vacant basement apartment caused him to contract the disease. The 

Superior Court (the Honorable Natalia Combs Greene) granted Call/D‘s motion in 

limine to exclude the testimony of Russell‘s designated causation expert and then 

granted Call/D‘s motion for summary judgment. Russell argues on appeal that 

Judge Combs Greene abused her discretion by ruling without considering his 

supplemental Super. Ct. Civ. R. 26 (b)(4) statement and also that she erred in 

granting Call/D‘s motions in limine and for summary judgment. We disagree and 

therefore affirm. 

I. Factual and Procedural Background

The following background facts, which we consider in the light most 

favorable to Russell,1are undisputed. In 2004, Russell leased an apartment on the 

second floor of 5218 Fitch Street, S.E. (Apartment 6), and lived there until May 

2011. Sometime during the fall of 2010, the tenants living in the basement-level 

 

1

 ―This court reviews a summary judgment decision de novo, construing the 

facts independently in the light most favorable to the nonmoving party.‖ Ivey v. 

District of Columbia, 949 A.2d 607, 611 (D.C. 2008).
3

Apartment 1 vacated the premises, leaving behind their cats. The windows to 

Apartment 1 were left open, allowing the cats (and perhaps other animals) to enter 

and exit the vacant apartment. As a result, feces and dead animals were on the 

floor of the abandoned apartment, and the apartment had a horrible stench. The 

deposition testimony also establishes that in November 2010, a pipe burst in 

Apartment 1, causing flooding in the apartment. Additionally, sometime during or 

before May 2011, sewage and sewage-contaminated water backed up and 

overflowed into Apartment 1, covering its floor with a half-inch to inch of water 

that, at one point, also overflowed into the adjacent hallway. A video recording 

made on May 28, 2011 — after Russell had fallen ill with Legionnaires‘ disease —

shows that the apartment was still filthy at that time, with standing pools of water 

on the floor. 

Around May 8, 2011, Russell noticed that the water coming out of the 

faucets in his apartment smelled bad and was discolored for several moments 

before running clean. Sewage or sewage-like water would also bubble up out of 

his drains after use. During early May 2011, the entire apartment building also 

began to smell, prompting residents to make calls to management starting around 

May 9, 2011. 
4

On May 10, 2011, Russell began to feel fatigued. Over the next few days, 

he felt increasingly worse. On May 21, 2011, when he was barely able to stand, he 

went to the hospital and was diagnosed with Legionnaires‘ disease, a serious form 

of pneumonia. Before the illness, Russell was a very healthy 39-year-old who 

routinely engaged in vigorous exercise. 

The parties‘ designated experts agree that Legionella bacteria, the cause of 

Legionnaires‘ disease, infect humans through the inhalation of contaminated 

airborne water droplets; that is, the water source containing the bacteria must be 

aerosolized and inhaled. Legionnaires‘ disease has an incubation period of 2-14 

days, meaning that ―symptoms typically manifest within 2 to 14 days after the 

exposure.‖ 

During the two weeks before he became symptomatic, Russell went to many 

different places. He worked five days a week for ADT Security Systems as a 

service technician, a job that required him to go to an average of seven different 

locations every day. From May 6-8, 2011, Russell and his girlfriend were on a 

weekend trip to Bryce Resort, a ski resort in Mount Jackson, Virginia, where, 

according to the girlfriend‘s deposition testimony, he took at least one shower. 
5

No samples were taken of the stagnant water in Apartment 1 before the 

apartment was professionally cleaned. Testing performed in September 2011 on 

water from taps and drain traps in Apartment 6 (to which Russell never returned 

after he was stricken in May 2011) uncovered no Legionella bacteria. As far as the 

record reveals, no one else living in the Fitch Street apartment building and no one 

else who visited Bryce Resort during the same time period when Russell was there 

contracted Legionnaires‘ disease. 

As noted above, Russell filed his lawsuit in June 2012. On February 5, 

2013, he served Call/D with a Rule 26 (b)(4) statement in which he designated 

Dr. Steven Zimmet, a pulmonologist who treated Russell when he had 

Legionnaires‘ disease, as an expert who would testify as to ―how Legionnaires‘ 

disease is contracted in general and specifically how Plaintiff contracted it due to 

his exposure to fumes and smells at his apartment building.‖2 No expert report or 

academic articles were attached to the Rule 26 (b)(4) statement. Call/D‘s attorneys 

deposed Dr. Zimmet on April 19, 2013. Although Russell‘s counsel provided Dr. 

Zimmet with two academic articles regarding Legionella bacteria immediately 

before the deposition, Dr. Zimmet testified that he did not rely on these articles in 

 

2

 Dr. Zimmet estimated that, in his clinical practice, he had each year 

evaluated ―one or more‖ patients who had Legionnaires‘ disease. 
6

coming to the opinion about which he planned to testify at trial.3 Dr. Zimmet 

assumed that Russell had regularly walked through sewage water when entering 

the apartment building, and he opined that Russell thereby came into contact with a 

sufficient number of aerosolized Legionella bacteria so as to become infected. 

After the April 30, 2013, close of discovery, Call/D filed a motion in limine

to exclude Dr. Zimmet‘s testimony, arguing that his training and experience as a 

clinician in treating patients diagnosed with Legionnaires‘ disease did not render 

him qualified to pinpoint the source of Russell‘s exposure to Legionella bacteria. 

On October 15, 2013, Judge Combs Greene issued an Omnibus Order in which she 

granted Call/D‘s motion in limine to exclude Dr. Zimmet‘s testimony, reasoning in 

part that his testimony regarding the source of Russell‘s illness was ―entirely 

speculative.‖ That ruling was the premise for Judge Combs Greene‘s additional 

ruling that there was ―no genuine issue of material fact . . . as to [the] proximate 

cause‖ of Russell‘s illness and her granting of Call/D‘s motion for summary 

judgment. 

 

3

 In preparation for his deposition, Dr. Zimmet consulted only an online 

service called UpToDate, which he agreed was a ―quick way for a physician to 

make sure . . . he hasn‘t missed anything current[.]‖ 
7

II. Disregard of the Supplemental Rule 26 (b)(4) Statement and the 

Decision Not to Hear Testimony from Dr. Zimmet

On September 18, 2013, Judge Combs Greene issued an order setting 

September 26, 2013, as the date for a hearing on Call/D‘s motion in limine. She 

asked the parties to be prepared to address ―[t]he basis for Dr. Zimm[e]t‘s opinion 

that sewage is a possible source for Legionella bacteria,‖ the extent of 

Dr. Zimmet‘s ―knowledge concerning the sources of [the] infections‖ of his 

previous patients who had been diagnosed with Legionnaires‘ disease, and ―[a]ny 

and all scholarly literature Dr. Zimm[e]t used to guide or assist him in reaching his 

conclusion that sewage can be a source of the Legionella bacteria.‖ Judge Combs 

Greene also stated that, while she found Dr. Zimmet‘s attendance ―essential,‖ his 

attendance would be excused if the scheduled hearing was inconvenient and if 

Russell could provide sufficient answers and documentation to address the court‘s 

concerns. Alternatively, Judge Combs Greene would ―consider Dr. Zimm[e]t‘s 

appearance by telephone‖ if the parties agreed. Two days before the scheduled 

hearing, apparently while Judge Combs Greene was on leave, Russell‘s counsel 

advised the judge‘s staff that Dr. Zimmet would be unable to attend a hearing on 
8

September 26 and requested a continuance until September 27.4 Staff instructed 

the parties to appear at the scheduled time. During the September 26 hearing, 

Russell‘s counsel gave the court the two academic articles counsel had shown 

Dr. Zimmet prior to his deposition.

On September 30, 2013, four days after the hearing, Russell filed a 

supplemental Rule 26 (b)(4) statement (―the supplemental statement‖). The 

supplemental statement slightly amended the earlier description of Dr. Zimmet‘s 

expected testimony, and attached to it were a number of journal articles and other 

publications. In her October 15, 2013, order granting Call/D‘s motion in limine, 

Judge Combs Greene stated that she ―did not view or consider‖ the supplemental 

statement in ruling on the motion. Russell now contends that Judge Combs Greene 

abused her discretion in ruling on the motion in limine without reading the

supplemental statement and without hearing testimony from Dr. Zimmet. 

This court reviews a trial judge‘s decision whether to accept a supplemental 

Rule 26 (b)(4) statement for abuse of discretion. See Ferrell v. Rosenbaum, 691 

A.2d 641, 646 (D.C. 1997). We ―take into account the reason for the supplement, 

 

4

 Russell thereafter filed a motion to the same effect. 
9

the importance of the proffered testimony and any prejudice to the opposing 

party.‖ Id. at 647. In this case, we can find no abuse of discretion in Judge Combs 

Greene‘s decision not to consider Russell‘s supplemental statement. Russell was 

made aware by (1) the questioning at Dr. Zimmet‘s deposition on April 19, 2013, 

(2) Call/D‘s May 15, 2013, motion in limine, and (3) the affidavits of Call/D‘s 

experts attached to Call/D‘s May 15, 2013, motion for summary judgment (to 

which Russell filed an opposition on May 24, 2013), that Call/D was challenging 

Dr. Zimmet‘s qualifications to testify, but Russell waited until September 30, 2013,

to file the supplemental statement. Russell provided Judge Combs Greene (and he 

has provided this court) with no explanation for the delay; quite the contrary, his 

counsel asserted that Dr. Zimmet‘s deposition was ―very clear[,]‖ never mentioned 

a need to supplement the expert witness statement, and did not request leave to do 

so. 

Nor do we discern that the information provided by the supplemental 

statement was important for appellant‘s case. The supplemental statement slightly 

modified the description of Dr. Zimmet‘s anticipated trial testimony: the earlier 

statement said that he would testify about how Russell contracted Legionnaires‘

disease ―due to his exposure to fumes and smells at his apartment building[,]‖

while the supplemental statement said that Dr. Zimmet would testify about how 
10

Russell contracted Legionnaires‘ disease ―due to his exposure to stagnant water

and their [sic] associated fumes and smells at his apartment building‖ (emphasis 

added). The supplemental statement‘s references to ―stagnant water‖ and 

―longstanding stagnant water‖ were new, but Judge Combs Greene could see, from 

Dr. Zimmet‘s deposition, that his opinion was that ―sewage water was the most 

likely source of [Russell‘s] exposure[,]‖ meaning that Russell cannot establish 

prejudice from the court‘s not having read the revised text.5

The publications attached to the supplemental statement and the citations to 

some of them in the text of the statement did add something new, because some of 

them pertain to investigations of the presence of Legionella bacteria in sewage 

 

5

 Russell‘s Reply Brief draws a distinction between ―stagnant water‖ and 

―sewer water,‖ apparently to suggest that the revised language in the supplemental 

statement did add something different that Judge Combs Greene needed to 

consider. Remarkably, the brief asserts that from the very beginning, ―this case 

has been about [Russell‘s]  ̳exposure to standing water in his apartment 

building[,]‘‖ and that ―[w]hether sewer water is a hospitable breeding ground for 

Legionella is simply not at issue in this litigation and amounts to a straw man 

argument.‖ That assertion cannot be squared with Russell‘s Complaint, which 

avers that his Legionnaires‘ disease was proximately caused by his exposure to raw 

sewage, or with his opposition to Call/D‘s motion for summary judgment, which 

repeats that claim. Moreover, Dr. Zimmet opined at his deposition that the 

apartment building was the most likely source of Russell‘s exposure to Legionella 

bacteria because of the ―contaminated sewer water‖ there. Therefore, if the 

references to ―stagnant water‖ in the supplemental statement were meant to be 

substantively different from the prior claims about sewage-contaminated water, 

that change, in itself, was reason for Judge Combs Greene to decline to consider 

the post-discovery-period supplemental statement. 
11

treatment plants. However, nothing in the supplemental statement indicated that 

Dr. Zimmet had approved the statement or had ever read the articles and 

publications attached to it.

6 Dr. Zimmet testified at his deposition that he arrived at 

his opinion about the source of Russell‘s exposure without relying on journal 

articles,7and, as Judge Combs Greene recognized, Call/D could rightly claim

prejudice from a late supplemental statement that ―would potentially subject them 

 

6

 Call/D may be correct that the court‘s disregard of the publications did 

not prejudice Russell even if Dr. Zimmet had read them. We say that because 

Judge Combs Greene could reasonably have found that the publications provided 

no support for Dr. Zimmet‘s opinion. One of the publications reports that ―the risk 

of legionellosis to sewage workers was considered low.‖ Another of the articles 

explains that L. pneumophila is ―the organism responsible for the majority (80%) 

of legionellosis outbreaks‖ and that the Legionella bacteria found in sewage 

samples were ―predominantly non-L. pneumophila species[.]‖ The article further 

states that using one method, Legionella pneumophila was recovered ―in only 10% 

of primary effluent samples and 5% of secondary effluent samples.‖ Under a 

different method, Legionella pneumophila was detected ―with much greater 

frequency[,]‖ although whether that method ―actually detected L. pneumophila [is 

unclear] since the PCR and plate culture methods did not support the DFA method 

findings.‖ The authors explain that the test results could have been a false reading

explained by antibodies having ―cross-reacted with other organisms in the 

sewage.‖ 

7

 Regarding the publications Russell‘s counsel handed to Judge Combs 

Greene in open court during the September 26 hearing, counsel incorrectly told the 

judge that Dr. Zimmet said at his deposition that he ―was going to rely upon‖ the 

publications. In fact, Dr. Zimmet testified at his deposition that the publications 

would not ―play[] any role in the opinions [he was] going to render in this case[.]‖ 

He further agreed that there was ―no peer-reviewed published literature that [he 

was] citing in support of [his] opinions‖ and that he was not relying on any specific 

literature ―to indicate that sewer water is a vector for distributing Legionnaire‘s 

[sic] disease or Legionella bacteria.‖ 
12

to different allegations . . . at a late stage of the litigation.‖

8

 French v. Levitt, 997 

A.2d 701, 704 (D.C. 2010).

As for the court‘s not hearing testimony from Dr. Zimmet before ruling on 

the motion in limine, Russell highlights Judge Combs Greene‘s statement (in the 

order setting the hearing) that the description of Dr. Zimmet‘s testimony in 

Russell‘s Rule 26 (b)(4) statement was ―very vague.‖ But Judge Combs Greene 

told the parties at the outset of the hearing that she had probably been ―overly 

 

8

 Judge Combs Greene explained at the September 26 hearing that Russell 

had to ―put [the literature he was relying on] out there so the other side knows, can 

question it, can contest that at the deposition and say [ ̳]did you know that this 

source that you relied on has been discredited by every major author, peer 

review,[‘] so on and so forth . . . and let the person say what they have to say about 

it.‖ 

An impetus for Russell‘s submitting the publications attached to the 

supplemental statement was no doubt that in May 2013, Call/D had filed affidavits 

from its experts stating, inter alia, that ―conditions favorable to Legionella are not 

normally found in sewage.‖ Thus, analogous to the situation in Ferrell, a case on 

which Russell relies, in which this court held that the plaintiff‘s supplemental Rule 

26 (b)(4) statement should have been considered by the trial court, ―the need for 

supplementation was caused by new information from‖ Call/D‘s experts. Ferrell, 

691 A.2d at 647. However, in Ferrell, the plaintiff‘s counsel advised defense 

counsel of the proposed expanded testimony of plaintiff‘s expert five days after 

learning certain factual information during defendant‘s deposition and served 

plaintiff‘s formal supplemental Rule 26 (b)(4) submission a few weeks later. Id. at 

645, 645 n.6. Here, by contrast, Russell‘s supplemental statement was served and 

filed over four months after Call/D had filed its experts‘ affidavits and its motions 

in limine and for summary judgment, and after the September 26 hearing on the 

motion in limine.
13

cautious‖ in scheduling the hearing and thought she could rule on the motion after 

rereading Dr. Zimmet‘s deposition, without hearing from him.9 We discern no 

reason to question Judge Combs Greene‘s assessment, especially since we, too, 

think that Dr. Zimmet‘s deposition furnished a sufficiently clear basis for the court 

to rule on the motion in limine.10 Thus, we cannot agree with Russell‘s claim that 

Judge Combs Greene abused her discretion by ruling ―when she lacked the very 

information . . . she needed to make an informed decision[.]‖ 

III. The Ruling on Call/D’s Motion In Limine

Russell contends that Judge Combs Greene also abused her discretion in 

excluding Dr. Zimmet‘s testimony, arguing that Dr. Zimmet‘s ―training and 

experience provided a sufficient foundation to permit his expert opinion testimony 

 

9

 Judge Combs Greene also told counsel at the outset of the hearing that her 

reason for not calling counsel and saying ―don‘t come in‖ was that she thought that 

one or both of the parties had ―wanted to make [her] aware of something‖ and thus 

would have objected to a postponement. 

10

 Russell complains that Dr. Zimmet could have testified regarding his 

experience with previous patients and his knowledge concerning the sources of 

their infections. But Dr. Zimmet had an opportunity to do that at his deposition 

(including during the questioning by Russell‘s counsel, when he simply agreed 

with counsel‘s vague leading question that ―what [he] did in this case‖ was ―tr[y] 

to figure out all of the possibilities that . . . might explain the illness . . . that [he is] 

trying to treat the patient for‖), and did not do so. 
14

on the issue of the source of [Russell‘s] exposure to Legionella bacteria.‖ We 

review a trial court‘s decision about whether to admit expert testimony for abuse of 

discretion. District of Columbia v. Anderson, 597 A.2d 1295, 1299 (D.C. 1991). 

That means that our review is deferential, as ―deference . . . is the hallmark of 

abuse of discretion review.‖ General Elec. Co. v. Joiner, 522 U.S. 136, 143

(1997); see also Girardot v. United States, 92 A.3d 1107, 1113 (D.C. 2014) (―The 

concept of  ̳exercise of discretion‘ is a review-restraining one.‖ (quoting Johnson v. 

United States, 398 A.2d 354, 362 (D.C. 1979))). Accordingly, the trial court‘s 

decision will be ―sustained unless it is manifestly erroneous.‖ Coates v. United 

States, 558 A.2d 1148, 1152 (D.C. 1989). 

To be permitted to testify as an expert, a witness ―must have sufficient skill, 

knowledge, or experience in that field or calling as to make it appear that his 

opinion or inference will probably aid the trier in his search for truth[.]‖ Dyas v. 

United States, 376 A.2d 827, 832 (D.C. 1977) (citation omitted). ―Implicit in that 

requirement is that the expert [must] have a reliable basis for [his] theory steeped 

in fact or adequate data, as opposed to offering a mere guess or conjecture.‖ 

Perkins v. Hansen, 79 A.3d 342, 345 (D.C. 2013) (citation and internal quotation 

marks omitted). ―The purpose of expert opinion testimony is to avoid jury findings 

based on mere speculation or conjecture[,]‖ and thus the court must weigh the 
15

―sufficiency of the foundation for those opinions . . . with this purpose in mind.‖ 

Washington v. Washington Hosp. Ctr., 579 A.2d 177, 181 (D.C. 1990). ―Without 

more than credentials and a subjective opinion, an expert‘s testimony that  ̳it is so‘ 

is not admissible.‖ Wilson Sporting Goods Co. v. Hickox, 59 A.3d 1267, 1273 

(D.C. 2013) (quoting Viterbo v. Dow Chem. Co., 826 F.2d 420, 424 (5th Cir. 

1987)). ―Expert testimony may be excluded when the expert is unable to show a 

reliable basis for their theory.‖ Haidak v. Corso, 841 A.2d 316, 327 (D.C. 2004).

In this case, Judge Combs Greene articulated many reasons for her ruling 

that Dr. Zimmet was ―not qualified to testify as to the source of [Russell‘s] 

disease,‖ among them that Dr. Zimmet had never been trained in or ―involved with 

the identification of the source of exposure‖ of Legionnaires‘ disease, was ―not 

aware of any specific type of bacteria present in sewage water[,]‖ ―did not indicate 

any literature to support his belief that Legionella bacteria could exist in sewage 

water[,]‖ had ―never had responsibility for determining the source of a person‘s

Legionella bacterial exposure as part of his clinical practice[,]‖ did not know ―what 

strains of Legionella bacteria are most commonly associated with Legionnaire‘s

[sic] Disease in humans[,]‖ was not familiar with the temperatures at which or the 

conditions under which Legionella bacteria amplify, and had ―no data to support 

his opinion that Legionella bacteria [were] at sufficient levels [in Apartment 1] to 
16

cause [Russell‘s] Legionnaire‘s [sic] disease.‖ Dr. Zimmet‘s deposition answers

support these findings as well as Judge Combs Greene‘s finding that his opinion 

testimony on causation was ―without factual basis.‖

It is true that, as Russell emphasizes, an expert witness may rely upon his 

experience alone when providing an opinion, see Perkins, 79 A.3d at 345 (―[A] 

physician‘s experience may provide a reliable basis for his or her expert opinion.‖), 

and that an expert witness need not cite a peer-reviewed journal article as the basis 

for every opinion he provides and need not use the ―data that will provide the 

highest degree of certainty[.]‖ Id. at 346. In addition, ―[w]here an expert 

otherwise reliably utilizes scientific methods to reach a conclusion, lack of textual 

support may  ̳go to the weight, not the admissibility‘ of the expert‘s testimony.‖ 

Knight v. Kirby Inland Marine Inc., 482 F.3d 347, 354 (5th Cir. 2007). But, as 

Judge Combs Greene recognized, Dr. Zimmet relied on neither experience in 

investigating the source of a Legionella infection, nor knowledge about what had 

been determined to be the source of his other Legionnaires‘ disease patients‘ 

exposures, nor peer-reviewed journal articles, nor data from testing at the 

apartment building, and he did not utilize a scientific method to conclude that 
17

Legionella bacteria were present in the Fitch Street apartment building.11 Instead, 

as he acknowledged during his deposition, he ―essentially ma[de] the assumption 

. . . that the water in the apartment [building] contained amplified levels of 

Legionella bacteria.‖ He acknowledged that the same logic by which he 

eliminated the environment at the Bryce Resort as a source of Russell‘s infection 

— that ―[n]obody else got sick‖ there — was equally applicable to the Fitch Street 

apartment building (since no one else living in the apartment building got sick), 

and he offered only the ―belie[fs]‖ that ―taking a couple of showers‖ at Bryce 

would not be enough to make the previously healthy Russell sick and that Russell 

―really had no other source of Legionella disease.‖12 

Further, Dr. Zimmet invoked ―common sense‖ and ―intuiti[on]‖ as his basis 

for saying that the Bryce Resort was not a probable source of Russell‘s infection 

 

11

 ―Scientific method‖ refers to ―[t]he process of generating hypotheses and 

testing them through experimentation, publication, and replication.‖ BLACK‘S LAW 

DICTIONARY 1547 (10th ed. 2014).

12

 Dr. Zimmet did not need to rule out every possible alternative source of 

exposure. See Westberry v. Gislaved Gummi AB, 178 F.3d 257, 265 (4th Cir. 

1999). But, to offer an opinion to a reasonable degree of medical certainty, he

needed — and, in Judge Combs Greene‘s reasonable estimation, he lacked — ―an 

objectively well founded conviction that the likelihood of one cause [of Russell‘s 

exposure was] greater than any other[.]‖ Robinson v. Group Health Ass’n, Inc., 

691 A.2d 1147, 1150 (D.C. 1997) (quoting Clifford v. United States, 532 A.2d 628, 

640 n.10 (D.C.1987)). 
18

and that Russell‘s ―walk[ing] through . . . sewer water‖ at the apartment building 

was the likely culprit.13 And, when asked at his deposition about his ―training, 

knowledge and experience with respect to being able to connect a diagnosis of 

Legionnaire‘s [sic] disease to a suspected source[,]‖ Dr. Zimmet answered that the 

basis of his opinion in this case was that ―[y]ou know it when you see it.‖ That 

response — I know it when I see it — was the ―quintessential ipse dixit

justification.‖ TASER Int’l, Inc. v. Karbon Arms, LLC, No. 11–426, 2013 WL 

6773663, at *1 (D. Del. Dec. 19, 2013). Judge Combs Greene was not required to 

admit opinion evidence that was ―connected to existing data only by the ipse dixit

of the expert.‖ Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 157 (1999)

(quoting Joiner, 522 U.S. at 146); cf. Brown v. Bray & Gillespie III Mgmt., LLC, 

No. 6:06-cv-661-Orl-22GJK, 2008 WL 2397601, at *6 (M.D. Fla. June 10, 2008) 

(concluding that an internist‘s opinion that plaintiffs ―contract[ed] an acute 

Legionella infection as a result of [their] hotel stay . . . at the Sea Garden Inn in 

 

13

 We note, too, that although Russell testified that he sometimes checked 

on an elderly woman who was living on the basement level of the apartment 

building, the deposition testimony contains no evidence that Russell actually 

―crossed through‖ or ―walked through‖ any water or did so ―twice a day,‖ as 

Dr. Zimmet assumed. Russell‘s testimony indicated that, upon entering the 

apartment building on the ground floor, he needed to walk up to his apartment 

rather than down to the basement level. He also testified that he at no time entered 

Apartment 1. Judge Combs Greene could reasonably ―conclude that there [was]

simply too great an analytical gap between the data and the opinion [Dr. Zimmet] 

proffered.‖ Joiner, 522 U.S. at 146.
19

Florida‖ ―lack[ed] a substantial basis,‖ and explaining that ―[t]he opinions of an 

expert will not be accepted if based on merely the ipse dixit of the expert‖).14

Russell further contends that Judge Combs Greene ―impermissibly 

demanded that [he] adduce direct (rather than circumstantial) evidence of the 

presence of Legionella bacteria in the building before permitting Dr. Zimmet to 

testify.‖ While we agree that the source of a plaintiff‘s Legionnaires‘ infection can 

be proven by (and perhaps can be proven only by) circumstantial evidence,15 we 

 

14

 We also defer to Judge Combs Greene‘s reasoning that, in light of the 

facts that the sewage-contaminated water in the apartment building had not been 

tested for Legionella bacteria and that Dr. Zimmet had cited no basis in the 

scientific literature for his conclusion that the sewage water was the most likely 

source of exposure, to allow his speculative testimony to that effect would have 

been more prejudicial than probative. 

15

 Epidemiological evidence, which typically is used to prove the source of 

a Legionnaires‘ outbreak, see Brown v. Bray, 2008 WL 2695230 at *2 

(―[E]pidemiologic data indicated that the source of the outbreak was the hotel.‖), is

circumstantial evidence. See In re Hanford Nuclear Reservation Litig., 1998 WL 

775340, at *5 (E.D. Wash. Aug. 21, 1998) (―[P]laintiffs here are forced to rely on 

experts who present circumstantial proof of causation, in particular, 

epidemiological proof.‖); Land v. United States, 37 Fed. Cl. 231, 235 (Fed. Cl. 

1997) (―[T]he two primary forms of circumstantial evidence in a toxic tort case are 

etiological evidence and epidemiological evidence.‖) (citing Renaud v. Martin 

Marietta Corp., 749 F. Supp. 1545, 1553 (D. Colo. 1990)); see also Silivanch v. 

Celebrity Cruises, Inc., 171 F. Supp. 2d 241, 255 (S.D.N.Y. 2001) (describing 

circumstantial evidence that sufficed to prove causation: the Legionella bacteria 

recovered from the sand filters of a cruise ship spa system ―were indistinguishable 

from organisms found in the respiratory system of one of the victims of the 

outbreak‖).
20

reject Russell‘s claim of error, because we do not agree that Judge Combs Greene 

excluded Dr. Zimmet‘s testimony on the ground that he had no direct evidence of 

the presence of Legionella in the building. Judge Combs Greene found it 

―significant[]‖ that Dr. Zimmet ―did not indicate any literature to support his belief 

that Legionella bacteria could exist in sewage water.‖ She reasoned that 

Dr. Zimmet‘s opinion that sewage water was the most likely source of Russell‘s 

exposure was ―not supported by published scholarly data‖ and that Dr. Zimmet 

was ―unfamiliar with several areas of scientific scholarship or clinical work that 

might provide a substantive basis for the conclusion offered‖ (emphasis added). 

She also cited portions of Dr. Zimmet‘s deposition in which he testified that he did 

not regularly read ―published medical or scientific or hygiene literature with 

respect to Legionnaire[s‘] disease‖; that he had formed his opinions in this case 

before seeing, just prior to his deposition, an article Russell‘s counsel had given 

him entitled ―Health Effects of Sewage Aerosols: Additional Serological Surveys 

and Search for Legionella Pneumophila in Sewage‖; that the article would not play 

a role in the opinions he would render in the case; and that he had not reviewed any 

peer-reviewed and published literature discussing the prevalence of Legionella in 

sewage-contaminated water. In addition, Judge Combs Greene explicitly 

recognized that case law has held that ―it is not an abuse of discretion for courts to 

allow expert testimony when the expert did not conduct independent testing‖ and 
21

that ―[a]s long as the expert relied on published data generated by another expert in 

the pertinent field, the opinion is admissible.‖ We read all these statements in the 

Omnibus Order as indicating that even though Dr. Zimmet had no direct evidence 

that Legionella bacteria were in water at the apartment building, Judge Combs 

Greene would likely have permitted him to testify if he had had a basis in the 

scientific literature to say that the sewage-contaminated water in the basement of 

the apartment building was a more likely source of Russell‘s exposure than a 

shower at Bryce Resort or any of the scores of locations Russell had visited 

through his work and other activities during the incubation period.

We next address Russell‘s contention that Judge Combs Greene applied a 

legally erroneous standard in ruling on the motion in limine. He argues that the 

judge held Dr. Zimmet ―to a burden of proof greater than the preponderance of 

evidence (more likely than not) standard[.]‖16 The evidence of this error, he 

asserts, is the following statement on page 9 of Combs Greene‘s Omibus Order: 

―Dr. Zimmet concludes that he  ̳believes‘ that the sewage water was the most 

likely source of exposure as compared to the other possible sources because it 

looked like a  ̳cesspool‘‖ (bold font in the original). We note that Judge Combs 

 

16

 A trial court erroneously exercises its discretion if it applies an incorrect 

legal standard. See Herbin v. United States, 683 A.2d 437, 443 (D.C. 1996).
22

Greene made a similar statement in footnote 6 of the Omnibus Order: ―Dr. 

Zimmet does not, in his deposition, states [sic] that he believes the sewage was the 

actual source of the Legionella bacteria. Rather, . . . he  ̳believes‘ the apartment 

complex was the most likely source‖ (bold font in the original). 

Russell is correct that his burden was to prove the ―most likely‖ source of 

his exposure. See Snyder v. George Washington Univ., 890 A.2d 237, 248 (D.C. 

2006) (―We require only that a causation expert state an opinion, based on a 

reasonable degree of medical certainty, that the defendant‘s conduct was a likely 

cause of the plaintiff‘s injuries.‖). Because it is not clear to us what Judge Combs 

Greene intended to convey through her emphasis on the words ―believes,‖ 

―actual,‖ and ―most likely,‖17 we are skeptical of Russell‘s claim that she 

misapprehended the legal standard or incorrectly applied it. We are, however, 

satisfied that even if Judge Combs Greene erroneously held Russell to a heightened 

standard of proof, the basis for her ruling that Dr. Zimmet was not qualified to 

 

17

 At one point, Judge Combs Greene appeared to be distinguishing 

between Dr. Zimmet‘s opinion that the apartment building ―was the actual and 

only source of [Russell‘s] Legionnaire‘s [sic] Disease‖ and his not opining that the 

sewage ―was the actual source of the Legionella bacteria‖ (emphasis in original). 

At another point, however, she characterized Dr. Zimmet‘s view as an opinion that 

the building ―was the most likely source of exposure as compared to other possible 

sources ([Russell‘s] job and Bryce Resort)‖ because of the contaminated sewer 

water. 
23

testify as an expert on causation was that Dr. Zimmet did not provide ―any real 

basis (based on facts or science) for his opinions.‖ That was a sufficient basis for 

precluding him from testifying as a causation expert regardless of the degree of 

certainty that was required. For that and all the foregoing reasons, we will not 

disturb Judge Combs Greene‘s ruling on the motion in limine. 

Russell argues in the alternative that Dr. Zimmet was entitled to testify about 

the source of Russell‘s exposure to Legionella as a fact witness rather than as an 

expert witness. It is true that ―[i]nsofar as a physician obtains and develops his 

information and opinions in the course of his treatment of a patient, he becomes an 

 ̳actor or viewer‘ who should be treated as an ordinary witness rather than as an 

expert covered under Rule 26 (b) (4).‖ Adkins v. Morton, 494 A.2d 652, 657 (D.C. 

1985) (explaining that ―the crucial inquiry is whether the facts and opinions 

possessed by the expert were obtained for the specific purpose of preparing for the 

litigation in question‖); Gubbins v. Hurson, 885 A.2d 269, 277 (D.C. 2005) 

(quoting Adkins and reasoning that ―Dr. Kelly‘s opinion, which he expressed to 

Gubbins while she still was under his care, that her nerves were injured by the 

medication she received during her surgery‖ ―clearly fell within this  ̳exempt-from-
24

Rule 26 (b) (4)‘ category‖).18 However, ―a witness may be an  ̳expert‘ as to some 

matters and an  ̳actor‘ as to others.‖ Id. (internal quotation marks omitted). The

question here is one of timing: When did Dr. Zimmet reach the opinions about 

which Russell sought to have him opine? If he reached them only ―while 

preparing for his trial appearance[,]‖ id. at 278, he needed to be qualified as an 

expert to be permitted to testify.

What the record reveals is the following: Dr. Zimmet testified that he had 

formulated his opinions as of February 5, 2013 (the date of Russell‘s previous Rule 

26 (b)(4) statement). There was evidence that, as recently as September 2012,

Dr. Zimmet or (much more frequently) his staff had provided care to Russell in 

connection with a blood clot in his leg that stemmed from his being bedridden for 

weeks while recovering from Legionnaires‘ disease. However, Russell testified 

that the last time he went to any doctor for anything relating to the Legionnaires‘

disease itself was in June 2011. In addition, Dr. Zimmet testified that Russell‘s 

diagnosis of Legionnaires‘ disease was made by other doctors prior to 

Dr. Zimmet‘s involvement in Russell‘s treatment, and one of those doctors (―the 

 

18

 See also Folks v. District of Columbia, 93 A.3d 681, 685 (D.C. 2014) 

(―[T]he medical records suggest that the treating physicians would be able to 

testify at trial about their opinions on the issue of causation based on the 

information that they had obtained in their treatment of Mr. Folks.‖).
25

infectious disease doctor‖) wrote in the medical records (apparently incorrectly) 

that Russell reported that he had water leakage in his apartment from a ventilation 

system and attributed the Legionella exposure to that.19 Dr. Zimmet described the 

―grilling‖ about ―[w]hat‘s your exposure‖ that ―we‖ doctors conduct when 

encountering a patient who has Legionnaires‘ disease, but also explained that 

Russell was asked about exposures ―at the time he came in the hospital in his May 

admission,‖ clarified that Russell did not answer such questions to Zimmet 

specifically, and acknowledged he had never ―had the responsibility for 

determining the source of an individual‘s Legionella bacterial exposure as part of 

[his] clinical practice.‖ Further, Dr. Zimmett had never visited the Fitch Street 

apartment building. He relied on what he read in Russell‘s deposition transcript 

and other depositions and on what he saw in the video of Apartment 1 for his 

knowledge of the conditions that existed in the building, and, importantly, he did 

not see the video or any photos of Apartment 1 until the day of his deposition, 

which was April 19, 2013.

20

 In short, the record provides no foundation for a 

 

19

 Russell stated during his deposition that there were no ventilation ducts 

in his apartment and that he had never ―spent any time in a residence where a 

ventilation system leaks,‖ and one of Call/D‘s experts also stated in his expert 

report that ―[t]here is no vent system, no central air system and no air ducting 

system that could have dripped water into [Russell‘s] apartment.‖ 

20

 Russell‘s girlfriend, who made the video of the standing water in 

Apartment 1, testified that she decided to do this on her own after hearing Russell‘s 

(continued...)
26

conclusion that Dr. Zimmet ―formulated the opinions in question while he was 

treating‖ Russell, Gubbins, 885 A.2d at 278, rather than in preparation for his 

deposition and for trial, such that it was error not to permit him to present the 

opinions as a fact witness.

IV. Summary Judgment

Russell‘s final contention is that he presented sufficient circumstantial 

evidence for a reasonable jury to fairly infer that Legionella bacteria were present 

in his apartment building and that he was exposed to the bacteria there. He argues 

that whether sewer water is a hospitable breeding ground for Legionella is a 

disputed issue that could not be resolved on summary judgment. We can agree 

with the latter contention, but the problem for Russell, who bore the burden of 

proof, was that, upon the court‘s ruling on the motion in limine, he was left without

an expert to testify that sewage-contaminated water likely contains a strain or 

strains of Legionella associated with Legionnaires‘ disease and that Russell‘s 

 

(...continued)

doctors say ―that his illness was a result of some sort of bacteria in water.‖ Her 

thinking was that ―maybe this [i.e., the conditions in Apartment 1] contributed to 

[Russell‘s illness].‖ Explaining why he did not go back to Apartment 6 after he 

was discharged from the hospital, Russell testified non-specifically that ―[d]octors‖ 

(he had ―seven doctors‖) told him not to breathe the air in his apartment. He did 

not attribute that advice to Dr. Zimmet.
27

exposure to sewage-contaminated water was the likely source of his illness. 

Russell needed to prove more than the ―bare possibility‖ that the contaminated 

water in the apartment building was the exposure source. Ferrell, 691 A.2d at 650.

Meanwhile, Call/D‘s environmental health expert John David Krause, whose 

affidavit describes his involvement in ―at least 10 investigations involving 

Legionnaires‘ disease‖ and cites his consideration of the ―relevant peer-reviewed 

scientific literature,‖ was poised to testify that ―Legionella are not normally found 

in sewage‖; that Legionella generally ―compete[] poorly with other bacteria in the 

environment[,]‖ which ―typically out compete and may even prey upon 

Legionella‖; and that ―aerosols of water droplets, such as those created by 

showering, are capable of carrying Legionella bacteria[.]‖

21 Call/D‘s expert Tim 

Keane, a water treatment consulting engineer who runs a company called 

Legionella Risk Management, Inc., and whose expert report describes his ―lead 

role in [Legionella] outbreak investigations‖ for state and county health 

departments, was prepared to testify that 24% of Legionnaires‘ outbreaks are 

 

21

 To be sure, Russell filed a motion in limine (on which the court never 

ruled) to strike Krause‘s testimony. However, Russell‘s argument was that Krause 

should not be allowed to testify that Legionnaires‘ disease ―cannot be contracted 

through the respiration of fumes . . . or . . . odors‖ or that ―a specific determination 

of source and exposure pathway is required in order to establish causation with 

regard to Legionella exposure.‖ We cite only other opinions by Krause.
28

associated with travel and that travel-related outbreaks are difficult to detect 

because of the dispersal of persons from the source of the outbreak; and that 

samples of stagnant water taken from Apartment 6, which Russell had vacated, in 

September 2011 were negative for Legionella.

22 In addition, Call/D‘s expert 

Dr. Hung Cheung, a specialist in environmental medicine who had testified as an 

expert in epidemiology and toxicology, was poised to testify, inter alia, that 

Russell‘s visit to Bryce Resort was consistent with the incubation period for 

Legionnaires‘ disease.

23 Reviewing the matter de novo, we conclude that, 

presented with the foregoing and other testimony by Call/D‘s experts and no expert 

causation testimony to the contrary,24 a jury would have had no basis other than 

speculation for finding that sewage-contaminated water or sewage vapors at the 

 

22

 Russell filed a motion in limine (on which the court never ruled) to strike 

Keane‘s testimony, but the specific opinions he asked the court to strike were as to 

other points.

23

 Again, Russell filed a motion in limine (on which the court never ruled) 

to strike Dr. Cheung‘s testimony, but the specific opinions he asked the court to 

strike were as to other points.

24

 In his motion in the trial court to strike Keane‘s testimony, Russell 

suggested that this is a case ―where the jury can make the decision on medical 

causation without expert testimony[,]‖ but in his briefs on appeal he does not 

appear to take issue with Judge Combs Greene‘s finding that ―determining the 

source of contracting Legionnaire[s‘] Disease is beyond the  ̳ken of the average 

layman.‘‖
29

apartment building were the source of Russell‘s Legionella exposure.

25

 

Accordingly, Judge Combs Greene did not err in granting summary judgment in 

favor of Call/D.

For the foregoing reasons, the judgment of the trial court is

Affirmed.

 

25

 Cf. Sudbeck v. Sunstone Hotel Props., Inc., No. 2:04-cv-1535, 2006 WL 

2728624, *8 (D. Ariz. July 26, 2006) (reasoning that even where the evidence 

established that plaintiff contracted Legionnaires‘ disease sometime prior to July 8, 

2002, and stayed at the defendant‘s resort between June 25 and 27, 2002, i.e., 

within the incubation period of the Legionella pneumophila bacteria, and even 

where there was evidence that Legionella bacteria were found in water samples 

collected at the resort in May 2003, ―it would be sheer speculation to say that it is 

more likely than not that the bacteria was present at the resort in June 2002 when 

[plaintiff] was a guest‖).