Appellant contends the trial court erred: (1) by not exempting appellant’s expert witness from the trial court’s sequestration of all witnesses; (2) by allowing appellee’s counsel, over objection, to assert in his opening statement that appellant was contributorily negligent; and (3) by denying appellant’s motion for a new trial. We affirm the decision of the trial court.
On January 17, 1990, appellant, while being arrested during a domestic conflict, sustained a severe eye injury that resulted in the removal of his right eye. Appellant filed a complaint on July 3, 1990, alleging that excessive force was used during his arrest. During trial, the court made two rulings that are involved in this appeal: the rule on witnesses was invoked (witnesses were excluded from the courtroom, including an expert witness, except when testifying) and appellee’s counsel, over objection, was permitted to assert in his opening statement that appellant was contributorily negligent. The jury returned a verdict in favor of the District of Columbia. Appellant’s motion for a new trial was denied.
The exclusion of witnesses from the courtroom during trial is a matter within the discretion of the trial court.
See Matthews v. United States,
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 well-established 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.,
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. 2 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 ex *319 pert’s presence in the courtroom is “essential to the presentation of the party’s cause.” 3
Appellant’s next contention that the trial court committed prejudicial error by allowing a reference during opening argument to appellant’s alleged contributory negligence is without merit. Appellant fails to cite any supporting authority or show any specific prejudice suffered by the trial court’s ruling concerning appellee’s opening statement. Moreover, in reviewing the case cited by appellant upon his objection to the statement and subsequently instructing appellee’s counsel to eliminate all future references to issues concerning contributory negligence, it is clear from the record that the trial court actions were appropriate. 4
Finally, the trial court did not abuse its discretion in denying appellant’s motion for a new trial based,
inter alia,
on a claim that the jury verdict was against the weight of the evidence. A party has a right to a new trial only if an error at trial denied the party substantial justice.
See
Super.Ct.Civ.R. 59. Furthermore, a trial court’s denial of a motion for a new trial will not be reversed absent an abuse of discretion.
See, e.g., Queen v. District of Columbia Transit System, Inc.,
We conclude there was no error of law requiring reversal.
Affirmed
Notes
. Specifically, our review of the record reveals that the in-court testimony regarding the use of excessive force did not differ significantly from the reports and other documents available to appellant’s expert prior to trial.
Compare Malek v. Federal Ins. Co.,
. It is clear, however, that expert witnesses are not automatically exempted from a witness sequestration order.
See, e.g., Morvant, supra,
. The record before us reveals that appellant was not given the opportunity to explain why his expert should not be excluded from the courtroom. However, as stated, appellant has failed to demonstrate a clear abuse of discretion in this case. Nonetheless, given that experts often derive their opinions from many sources — including facts or data presented for the first time at trial — and that experts often advise counsel concerning important issues that develop throughout the course of litigation, the trial court should give parties a reasonable opportunity to explain the necessity of their expert's presence in the courtroom, and this was absent here.
. The case cited by appellant was
District of Columbia
v.
Peters,
