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DISTRICT OF COLUMBIA COURT OF APPEALS

No. 13-CT-128

CYNTHIA SANCHEZ, APPELLANT,

V.

DISTRICT OF COLUMBIA, APPELLEE.

Appeal from the Superior Court of the

District of Columbia

(CTF-9146-12)

(Hon. Heidi M. Pasichow, Trial Judge)

(Argued September 30, 2014 November 6, 2014)

Grey Gardner for appellant. 

John J. Woykovsky, Assistant Attorney General, with whom Irvin B. Nathan, 

Attorney General for the District of Columbia, Todd S. Kim, Solicitor General, and 

Rosalyn C. Groce, Deputy Solicitor General, were on the brief, for appellee.

Before BECKWITH and MCLEESE, Associate Judges, and NEWMAN, Senior 

Judge.

NEWMAN, Senior Judge: In this appeal, we are confronted with the

contention that a trial judge abused her discretion in sua sponte invoking the “rule 

on witnesses” to exclude an expert witness called by the defense from hearing a 

portion of the testimony of the principal fact and expert witness called by the 
2

government. We find an “erroneous exercise of discretion,” and the prejudice 

required to constitute an “abuse” thereof.1 Thus, we reverse.

In a bench trial, Sanchez was tried for driving under the influence, D.C. 

Code § 50-2201.05 (b)(1) (2009). The government‟s chief witness, Carll, a 

uniformed member of the U.S. Capitol Police, testified both as a fact witness and 

as an expert. On direct examination, he testified to the events leading to his 

stopping the vehicle that Sanchez was driving and that caused him to order her out 

of the vehicle. He testified that he administered three sobriety tests: the horizontal 

gaze nystagmus (HGN); the walk and turn; and the one-leg stand.2 He described

 

1

 (James W.) Johnson v. United States, 398 A.2d 354, 365-66 & n.9 (D.C. 

1979).

2

 In Pennsylvania v. Muniz, 496 U.S. 582, 585 n.1 (1990), the Supreme 

Court explained: 

The “horizontal gaze nystagmus” test measures the extent 

to which a person‟s eyes jerk as they follow an object 

moving from one side of the person‟s field of vision to 

the other. The test is premised on the understanding that, 

whereas everyone‟s eyes exhibit some jerking while 

turning to the side, when the subject is intoxicated “the 

onset of the jerking occurs after fewer degrees of turning, 

and the jerking at more extreme angles becomes more

distinct.” 1 R. Erwin et al., Defense of Drunk Driving 

Cases § 8A.99, pp. 8A-43, 8A-45 (1989). The “walk and 

turn” test requires the subject to walk heel to toe along a 

straight line for nine paces, pivot, and then walk back 

(continued...)
3

Sanchez‟s performances on these tests, which, coupled with the odor of alcohol on 

her breath, led him to conclude that she was operating her vehicle while under the 

influence. He arrested her. At the police station, Sanchez was advised by the 

officer who had transported her, Fleming, of the Implied Consent Act. She 

declined to be tested. The form reflecting her so declining was admitted into 

evidence.

After Carll testified on direct examination, counsel for Sanchez commenced 

cross-examination concerning his methodology in administering the field sobriety 

tests. He was soon interrupted when the trial judge summoned both counsel to the 

bench and stated:

At this point, I don‟t think that your expert should be in 

the courtroom. He‟s heard the direct examination, and I 

don‟t really think it‟s appropriate for him to hear the 

cross, so I‟m going to ask him to wait outside, because --

if the Government had objected to him hearing the direct, 

I might have considered excluding him, because it seems 

to me that the questions that you ask him must be based 

on the documents provided, could be based upon any CV 

that was provided or any discovery that was provided.

 

(...continued)

heel to toe along the line for another nine paces. The 

subject is required to count each pace aloud from one to 

nine. The “one leg stand” test requires the subject to 

stand on one leg with the other leg extended in the air for 

30 seconds, while counting aloud from 1 to 30. 
4

At this point, I don‟t see that it‟s appropriate for 

him to be in here for your cross examination. 

Counsel informed the court that he intended to have Carll demonstrate in as 

accurate and minute detail as possible exactly how he administered the three tests; 

that direct examination had not done so; that there was no video recordation of the 

testing; and that the defense expert, Palacios, needed to see Carll‟s demonstrations 

and further testimony in order to opine thereafter whether the tests had been 

performed in the proper manner. Counsel further attempted to inform the court of 

his need for the presence of the defense expert to assist him in formulating further 

cross-examination based on Carll‟s answers. This trial judge cut off the attempt to 

proffer and ruled:

I don‟t think he should be here to hear the witness‟s 

answers to your cross. You can ask him on direct. I 

think it gives you a completely unfair tactical advantage 

to have him sitting here on cross-examination when you 

can ask him questions on direct and the Government 

would get to cross him and determine what his answers 

will be. 

Counsel‟s subsequent attempts to have the trial judge reconsider this ruling were 

equally futile. As she informed counsel, “you‟re just going to have to make do 

with those circumstances the best way you can.” 
5

Palacios testified. He described the proper methodology for administering 

each of the tests. He opined that there were a number of defects with Carll‟s 

methodology. He further opined that based on the other testimony in the 

government‟s case—including the testimony of Fleming (the transport officer) that 

he observed no signs of impairment during the twenty or so minutes he interacted

with Sanchez—Carll “misinterpreted or mis-scored” the vertical nystagmus portion 

of the HGN test. He stated he could not be one hundred percent sure because of 

“not being able to see the officer administer the test.” However, if the tests are not 

administered properly “the validity of the test is compromised.” 

The defense presented a number of fact witnesses, including Sanchez, all of 

whose testimony was exculpatory. In addition, the defense called a second expert 

witness, Lappas, a forensic toxicologist who testified on a “common” and 

“accepted methodology” of retrograde extrapolation, which he described as a 

“method of estimating what a blood alcohol level concentration in blood was at 

some time prior to the time the analysis was conducted.” Given a hypothetical fact 

pattern tracking the defense evidence, he opined that the blood alcohol level of 

such a person at the time of Sanchez‟s arrest would have been between 0 and 0.04. 
6

As early as 1943, we held that a trial judge has discretion to exclude nonparty witnesses from hearing testimony at trial before testifying themselves, 

Bedrosian v. Wong Kok Chung, 33 A.2d 811, 812 (D.C. 1943)—the so-called “rule 

on witnesses.” We have reaffirmed this ruling repeatedly. See, e.g., Garmon v. 

United States, 684 A.2d 327, 328-29 (D.C. 1996); (James) Johnson v. District of 

Columbia, 655 A.2d 316, 317-18 (D.C. 1995) (per curiam); Matthews v. United 

States, 267 A.2d 826, 829 (D.C. 1970). We will reverse that decision only upon a 

showing of an “abuse of discretion.” Garmon, 684 A.2d at 328-29. See generally 

(James W.) Johnson, supra, 398 A.2d at 365-66 (delineating our abuse of 

discretion analysis).

We have also distinguished the testimony of “expert” witnesses and “fact” 

witnesses. (James) Johnson, supra, 655 A.2d at 318-19; compare Fed. R. Evid. 

615 (articulating the “rule on witnesses”), with Fed. R. Evid. 703 (1972) (“The 

facts or data in a particular case upon which an expert bases and opinion . . . may 

be those perceived by . . . the expert at or before the hearing.”). Our cases are in 

accord with this portion of Rule 703. See, e.g., In re Amey, 40 A.3d 902, 910 (D.C. 

2012) (relying on this portion of the rule); In re M.L., 28 A.3d 520, 530 n.21 (D.C. 

2011) (same). What we said in (James) Johnson, supra, about excluding expert 

witnesses bears repeating at length:
7

Nevertheless, while we find no abuse of discretion here, 

it is worth pointing out that in applying Rule 615 of the 

FEDERAL RULES OF EVIDENCE (discussing the exclusion 

of witnesses), federal courts have relied upon a wellestablished distinction between factual witnesses and 

expert witnesses: “We perceive little, if any, reason for 

sequestering a witness who is to testify in an expert 

capacity only and not to the facts of the case. . . . [T]he 

presence in the courtroom of an expert witness who does 

not testify to the facts . . . hardly seems suspect and will 

in most cases be beneficial, for he will be more likely to 

base his expert opinion on a more accurate understanding 

of the testimony as it evolves before the jury.” Morvant 

v. Construction Aggregates Corp., 570 F.2d 626, 629-30 

(6th Cir.), cert. dismissed, 439 U.S. 801 (1978); 

Polythane Systems v. Marina Ventures Int’l, 993 F.2d 

1201, 1209-10 (5th Cir. 1993), cert. denied, [510] U.S. 

[1116] (1994) (quoting Morvant, supra, 570 F.2d at 629-

30); United States v. Lussier, 929 F.2d 25, 30 (1st Cir. 

1991) (citing Morvant, supra, 570 F.2d at 629-30); 

United States v. Burgess, 691 F.2d 1146, 1157 (4th Cir. 

1982) (same); see also Malek [v. Fed. Ins. Co.], 994 F.2d

[49,] 54 [(2d Cir. 1993)] (the expert, whose assistance 

was important to plaintiff‟s case, was “not a „fact witness 

whose recollection might have been colored‟ by the 

testimony of other witnesses” and should have been 

allowed to remain in the courtroom) (citation omitted). 

Furthermore, under Rule 615, a party is entitled to show 

that his expert is “essential to the presentation of the 

party‟s cause” and therefore should not be excluded from 

the courtroom: “[W]here a fair showing has been made 

that the expert witness is in fact required for the 

management of the case, . . . we believe that the trial 

court is bound to accept any reasonable, substantiated 

representation to this effect by counsel.” Malek, supra, 

994 F.2d at 53-54 (discussing the Rule 615(3) exemption 

to witness exclusion and quoting Morvant, supra, 570 

F.2d at 630).
8

In the future, therefore, it would seem prudent for the 

trial court to consider the appropriate distinctions 

between factual witnesses and expert witnesses in 

deciding whether to exclude witnesses from the 

courtroom. In particular, the trial court should allow 

parties the opportunity to show any potential prejudice 

they may endure by the exclusion of their expert—i.e., 

why the expert‟s presence in the courtroom is “essential 

to the presentation of the party‟s cause.” 

655 A.2d at 318-19 (alterations in original) (footnotes omitted) (parallel citations 

omitted).

We reiterated this in Garmon, supra, 684 A.2d at 328-29 & n.2. We repeat 

it yet again here.

Here, the trial judge‟s reasons for excluding the defense expert are at odds 

with the rationale of permitting an expert to base an opinion on “facts made known 

to the expert at . . . the hearing.” Fed. R. Evid. 703 (1972). This is particularly so

in cases, including this case, in which the trial was a bench trial. See McKenzie v. 

United States, 659 A.2d 838, 841 (D.C. 1995) (presuming that, in a bench trial, the 

trial judge does not make improper use of evidence); (Melvyn A.) Johnson v. 

United States, 636 A.2d 978, 981 (D.C. 1994) (“[A] trial judge is presumed to 

know of the proper use of evidence.”). The proper exercise of discretion requires 
9

that a valid reason be given or be discernable from the record. (James W.) 

Johnson, supra, 398 A.2d at 367. The Federal Rules of Evidence and our prior 

decisions have established that the presence in the courtroom of expert witnesses is 

the norm, subject to exceptions. Here, the trial judge articulated no valid basis for 

the exclusion and none is discernable from the record. Considering the record 

before us, we have no hesitation in ruling that there was an erroneous exercise of 

discretion. 

In determining whether the erroneous exercise of discretion mandates 

reversal, and thus constitutes an abuse of discretion, we are mindful of the right of 

the defendant to present a defense. Chambers v. Mississippi, 410 U.S. 284, 302 

(1973); accord Taylor v. Illinois, 484 U.S. 400 (1988) (affirming the defendant‟s 

right to present witnesses in his defense). This right includes the right to confront 

witnesses and the right to introduce expert testimony. See, e.g., Benn v. United 

States, 978 A.2d 1257, 1269-70 (D.C. 2009); Robinson v. United States, 50 A.3d 

508, 523 (D.C. 2012). The right to present expert witnesses perforce includes the 

need to afford the expert appropriate means of gathering the “facts and data” upon 

which to base an opinion. In furtherance thereof, the defendant has a right to have 

his attorney consult with the expert during cross-examination of the government‟s 

expert so as to enable defense counsel to conduct meaningful cross-examination. 
10

While these rights, as with others, are subject to reasonable judicial limitations, 

those limitations must be imposed with the nature of the right in mind.

Here, the defense sought to have the expert, Palacios, observe Carll 

demonstrate in detail how he performed the three sobriety tests to provide Palacios 

the “facts and data” as foundation for his expert opinion on whether the tests were 

properly administered. Deprived of this opportunity by the trial court‟s ruling, the 

defendant had to rely on the ability of counsel to give a second hand description of 

the demonstration that Carll gave on cross-examination. The unsatisfactory nature 

of this as a substitute is perhaps highlighted by the government‟s closing argument, 

in which it urged the trial court to give limited weight to Palacios‟s testimony since 

he “was unable to see how [Sanchez] did on the test, to hear what she said, to see 

the position that they were done in.” The trial court did so, stating that Palacios 

“listened to the direct examination [of Carll] and he formulated some concerns 

based upon what he heard of the direct, but he also indicated, based upon what he 

didn‟t say, that the officer in some significant ways also conducted the tests in 

appropriate fashion.” 

In evaluating the issue of prejudice, we are mindful that Palacios was able to 

opine, based on what he heard on the direct examination of Carll and buttressed by 
11

the “facts” recited by the defense counsel from Carll‟s cross-examination, that 

Carll had not properly administered at least some of the tests. However, we are 

also mindful that the defendant was deprived of further opportunity to evaluate 

Carll‟s methodology directly and to point out any additional flaws as Palacios 

testified. In addition, the defendant was deprived of the use of her expert to 

meaningfully assist counsel in the conduct of the cross-examination of Carll. The 

trial court was left with, and credited, Carll‟s self-assurance that he had basically 

used proper methodology.

As the trial court recognized, the government‟s proof was far from 

compelling. It is with all these considerations in mind that we turn to the task of 

evaluating prejudice.

In doing so, we must look at the “totality of the 

circumstances” and decide whether we can say, “with fair 

assurance, after pondering all that happened without 

stripping the erroneous action from the whole, that the 

judgment was not substantially swayed by the error.” 

Kotteakos v. United States, 328 U.S. 750, 765 (1946). 

Only if the error “jeopardized the fairness of the 

proceeding as a whole,” or had a “substantial impact 

upon the outcome” of the case, may we reverse the 

judgment. [James W.] Johnson[, supra], 398 A.2d [at]

366.
12

Goines v. United States, 905 A.2d 795, 802 (D.C. 2006) (parallel citation omitted); 

accord In re L.C., 92 A.3d 290, 299-300 (D.C. 2014); King v. United States, 75 

A.3d 113, 120 (D.C. 2013); Heath v. United States, 26 A.3d 266, 281 (D.C. 2011); 

Russell v. United States, 17 A.3d 581, 588-89 (D.C. 2011); In re L.L., 974 A.2d 

859, 865 (D.C. 2009); Pannu v. Jacobson, 909 A.2d 178, 199 (D.C. 2006); Mercer

v. United States, 724 A.2d 1176, 1194 (D.C. 1999). 

Having done so, we reverse.3

So ordered.

 

3

 Sanchez also asserts that the trial judge‟s “apparent advocacy” violated her 

due process rights. See Haughton v. Byers, 398 A.2d 18, 20-21 (D.C. 1979); see 

also Knapp v. Kinsey, 232 F.2d 458, 465-66 (6th Cir. 1956). In addition to the sua 

sponte sequestration of Palacios, Sanchez points to what she claims was excess 

questioning of defense witnesses. See Haughton, supra, 398 A.2d at 21. Likewise, 

she complains about the judge‟s comments about the utility, or lack thereof, of 

Lappas‟s testimony on “retrograde extrapolation,” as well as her suggestion to 

Palacios that he was merely “second guessing” Carll. We need not decide, and do 

not decide, whether these matters provide independent grounds for reversal. 

Likewise, we need not decide, and do not decide, Sanchez‟s Confrontation Clause 

claim arising from the court‟s sua sponte limitation of her cross-examination of 

Carll for bias.