Aрpellant Gonzalez, a native of El Salvador, was convicted of distributing cocaine. 1 At trial he was assisted by a court-appointed interpreter. On appeal he contends (1) that the trial court erred in failing to make a preliminary determination that the interpreter was competent to translate the proceedings for him; (2) that the court impermissi-bly allowed an expert government witness to testify beyond the scope of his expertise; and (3) that a photograph taken at the time of his arrest should not have been admittеd into evidence. As to the first contention, we agree that the court erred but hold that the error was harmless. The second and third arguments are without merit. Accordingly, we affirm appellant’s conviction.
I
On the early evening of December 2, 1993, Metropolitan Police Officers Collis Timlick and Michelle Green set up an undercover narcotics operation in the 3100 block of Mount Pleasant Street, N.W. They entered the area wearing plain clothes and driving an unmarked car. While Green remained in the car, Timlick got out and walked over tо a man who was standing on the east side of the street. He told this man that he was looking for a “twenty,” meaning a $20 rock of crack cocaine. The man signaled Timlick to follow him across the street. There they met appellant Gonzalez, who was sitting on a bicycle in front of a pool hall. After Gonzalez and the unknown man had a conversation in Spanish, the three of them proceeded a short distance up the street to a bus stop in front of 3102 Mount Pleasant Street. When they reached the bus stop, Gonzalez and the other man again conversed in Spanish. Gonzalez then pulled three ziplock bags from inside the waistband of his trousers and gave all of them to the unknown man, who in turn gave two of them to Timlick. Each of the two bags contained a small rock-like object. Timlick then handed the unidentified man two pre-recorded $10 bills, 2 which he gave to Gonzalez.
*821 Officer Green testified that she watched the entire transaction from the car. She was able to discern Gonzalez on his red bicycle and could see that the three men were engaged in conversation. She also saw “arms moving back and forth” among the three men, but from her vantage point she could not tell whether any objects were passed from one to another.
When the transaction ended, Timlick returned to the car, while Officer Green broadcast a description of the two men she had seen engaged in an apparent drug transaction with her partner. 3 The two officers then followed Gonzalez, who was riding away on his bicycle, in order to keep the arrest team apprised of his whereabouts. After a few moments, Detective David Stroud, a member of the arrest team, radioed Timlick and Green and informed them that the team had stopped a suspect (Gonzalez) who matched the description and who had in his possession the two pre-recorded $10 bills. 4 Timlick and Green then drove their car past the point where the arrest team had stopped Gonzalez, and both of them positively identified him. 5 A later chemical analysis established that both of the rocks Timlick bought from Gonzalez were crack cocaine.
The government also presented, without objection, the expert testimony of Detective Charles Culver, who described to the jury the methods commonly used by drug sellers to distribute cocaine. He testified about the roles of “runners” and “holders” in the sale of drugs on the street, and explained that the runner sometimes receives drugs from the holder as compensation for his services. Detective Culver also outlined the procedures followed by the police department and the Drug Enforcement Administration in handling and sealing evidence recovered in narcotics cases. On direct examination Culver testified that the two roсks of cocaine in this ease had been properly heat-sealed and that the sealed envelopes showed no signs of tampering; however, he was not asked whether the envelopes containing the money seized from Gonzalez had been tampered with, or whether the proper chain of custody had been followed with respect to them. 6 Defense counsel elicited testimony from Detective Culver on cross-examination about the handling and processing of the two envelopes containing the monetary evidence.
Gonzalez was the sole defense witness. He testified that around 6:30 p.m. on the evening of December 2, he left his home to buy drugs and rode his bicycle to the 3100 block of Mount Pleasant Street. There he met his Mend and main drug supplier, “Carlos,” at a Seven-Eleven store. 7 When Gonzalez asked Carlos if he had any drugs to sell, Carlos told him to wait at a pool hall near the Seven-Eleven. Gonzalez then stood, *822 at the bus stop where Officers Timlick and Green had said the drug transaction occurred. Five minutes later Carlos arrived with a man that Gonzalez did not know, who turned out to be Officer Timlick.
Gonzalez then reached into his waistband, pulled out a $20 bill, and asked Carlos for drugs. Carlos took the money and, according to Gonzalez, engaged in a transaction with Timlick. When that was completed, Carlos turned back to Gonzalez, handed Gonzalez his $20 back, and told him that he had no more drugs to sell. 8 Gonzalez then left the bus stop and went to call his wife from a pay phone. 'While he was making the call, two police officers stopped him and said he was being detained. Gonzalez admitted that he had two $10 bills on him when he was stopped.
II
Gonzalez cоntends that the trial judge committed error by failing to ensure at the beginning of the trial that the court-appointed interpreter was competent. The government maintains that the issue of translator competence was not preserved for appellate review because defense counsel never objected at trial to the interpreter’s translations. Thus the government argues that the trial court did not commit plain error, see Watts v. United States, 362 A.2d 706, 709 (D.C.1976) (en banc), when it failed to interrupt the proceedings sua sponte and determine the competence of the interpreter.
The District of Columbia Interpreter Act, D.C.Code §§ 31-2701 et seq. (1993), provides in part:
Bеfore appointing an interpreter, an appointing authority shall make a preliminary determination that the interpreter is able to accurately communicate with and translate information to and from the communication-impaired person involved.
D.C.Code § 31-2704.
9
Because no such preliminary determination was made, Gonzalez argues that both his “statutory and constitutional due process rights to participate fully in his defense” were violated.
See Redman v. United States,
Before considering the merits of Gonzalez’s claim, there are two preliminary matters that we must address: whether Gonzalez sufficiently preserved this issue for appellate review, and if so, whether his claim should be reviewed for constitutional or non-constitutional harmless error. As to the first point, although a defendant has the right to an interpreter who is “competent to render accurate translations,”
United States v. Villegas,
Only if the defendant makes any difficulty with the interpreter known to the court can the judge take corrective measures. To allow a defendant to remain silent throughout the tñal and then, upon being found guilty, to assert a claim of inadequate translation would be an open invitation to abuse.
Id.
(quoting
Valladares, supra,
As the government acknowledges in its brief, at one point during the trial Gonzalez alerted the court to a problem with the interpreter’s translation. 13 On direct examination, defense counsel asked Gonzalez to describe how he had been stopped and arrested by the two police officers. The fоllowing exchange then took place:
THE WITNESS (through interpreter): When the car stopped in the middle of the street, a white woman got out and a black guy, a tall black guy, and they said, “You are detained,” and right away they got out of the car. I was on my bicycle. I didn’t think anything bad because I hadn’t done anything bad and they were just detaining me.
They asked me — they cheeked me out and the white woman said, “You are under arrest. You are not just detained. You are under arrest.”
You haven’t understood me well.
Mr. GEORGE [defense counsel]: Okay. Now—
THE COURT: Well, let me go back.
THE WITNESS (through interpreter): The interpreter hasn’t understood me well.
THE COURT: Okay. I want you to— Mr. Gonzalez, I wаnt you to restate what happened when the two people got out of the car.
THE WITNESS (through interpreter): When the two people got out of the car, they said to me, “Stop. Don’t move. You are not under arrest. You are just being stopped. We are going to search you.” I said okay, and she searched me and they took the money off of me, and then they handcuffed me there and they put me into the car.
In asserting that the issue was not adequately preserved, the government makes much of the fact that Gonzalez, rather thаn his counsel, brought this mistranslation to the court’s attention. However, we have never indicated
how
interpreter competence must be challenged in order to preserve the issue for appeal.
Cf. United States v. Urena,
The question that remains, then, is whether his claim should be reviewed for constitutional or non-constitutional error. Gonzalez assumes that his right to a competent interpreter is both statutorily and constitutionally mandated. The District of Columbia Interpreter Act, like its federal counterpart, 28 U.S.C. § 1827(d)(1) (1994), makes clear that the right to a competent interpreter is statutorily prescribed. No District of Columbia court has ever squarely decided whether the right to a translator is also guaranteed under the Constitution, but this court in a recent case has strongly suggested that the right at least has constitutional overtones.
See Kim Long Ko v. United States, supra,
note 14,
Turning to the substance of Gonzalez’s complaint, we begin by observing that
*825
the determination of the competence of an interpreter is a matter entrusted to the sound discretion of the trial court, and its decision will not be disturbed on appeal unless that discretion has been abused.
17
See, e.g., United States v. Urena, supra,
Applying this standard to the instant case, we observe,
first
of all, that the government’s case was “largely uncontradicted” and, “if credited by the jury, was compelling.”
Redman, supra,
was identified as one of the sellers, within minutes of the sale, by the undercover officer who had just bought the drugs, and who had an excellent opportunity to observe him. The force of the officer’s identification was enhanced by the recovery from [appellant’s] person of the two [prerecorded] bills ... which the officer had used to purchase the cocaine.
Id.
Second, it is obvious that Gonzalez himself, by pointing out the mistranslation to the court, had “some ability himself to monitor the questions and answers as conveyed by the interpreter.”
United States v. Urena, supra,
Although the government presented no formalized evidence of the interpreter’s competence, such as language degrees or certifications, the fact that the interpreter continued in that role ... suggests that the translation must have been competent enough to allow communications between the parties.
Thus, on the record before us, there is no indication of translator incompetence
18
which would justify a holding that the trial court abused its discretion or committed an error of constitutional magnitude.
See United States v. Urena, supra,
Ill
For the first time on appeal, Gonzalez contends that Dеtective Culver impermissi-bly testified outside the scope of his expertise by offering an opinion on cross-examination regarding the chain of custody of the monetary evidence. According to Gonzalez, the trial court committed plain error when it allowed the jury to hear this “highly prejudicial” testimony. This claim is without merit because the only error cited by Gonzalez is one of his own making, and it surely does not rise to the level of substantial prejudice which is required to show plain error. See Watts v. United States, supra.
Detective Culver was qualified as an expert on methods оf drug distribution and on police procedures used for handling and safeguarding narcotics evidence. This court has repeatedly upheld the admission of testimony from such an expert.
See, e.g., Griggs v. United States,
“The decision to admit expert testimony is within the broad discretion of the trial court, and a ruling either admitting or excluding such evidencе will not be disturbed unless manifestly erroneous.”
Gant v. United States,
[Tjhis court must determine, from the record on appeal, whether the trial court failed to exercise its discretion with reference to all the necessary criteria in admitting or excluding expert testimony.... “Otherwise the very reason for such defer ence — i.e., the trial court’s opportunity to observe, hear and otherwise evaluate the witness — will be compromised.”
Id.
at 110 (citations and footnote omitted). The “necessary criteria” to which
Gant
rеfers include “evaluating the competence of the proffered expert witness ...
assuring that the witness’ testimony does not exceed the scope of the expert’s qualifications approved by the court,
[and] ... preventing] an expert witness from preempting the function of the jury.”
Id.
(emphasis added);
see also United States v. Alonso,
The testimony that Gonzalez characterizes as being “highly prejudicial” was elicited not by the prosecutor but by defense counsel during his cross-examination of the expert witness. Thus the error that occurred, if any, was invited by defense counsel.
See Brown v. United States,
IV
Gonzalez finally contends that a photograph taken of him shortly after his arrest should not have been admitted into evidence. Because he admitted that he was the person arrested, Gonzalez maintains that his identity was never in dispute and, therefore, that the photograph wаs cumulative, irrelevant, and unduly prejudicial. This argument is merit-less because Gonzalez has failed to show any *827 prejudice that may have resulted from the photograph’s admission. We can discern no prejudice whatever.
When the government introduced the photograph at trial, defense counsel did not initially object. A few moments later, however, defense counsel approached the bench and objected because he had a notion there was a “mug shot rule” that barred the photograph’s admission. After consulting his trial manual, counsel apparently withdrew his objection. Nevertheless, when the court reconvened after a recess, the judge said that although he had previously admitted the photograph without objection, he was “currently admitting it over objection.” The court agreed with defense counsel that the mug shot rule was inapplicable because the evidence in question was an arrest photograph, not a mug shot. The purpose of the mug shot rule, the court explained, is to prevent undue prejudice by suggesting that a criminal defendant has a prior criminal record; 19 this photograph, however, conveyed no such suggestion because it was “incident to the arrest in this case ” (emphasis added).
It is well settled that a decision to admit or exclude photographs as demonstrative evidence is within the trial court’s sound discretion.
Clark v. United States,
Appellant’s conviction is therefore
Affirmed.
Notes
. D.C.Code § 33-541(a)(1) (1993).
. Earlier that day, Officer Green had obtained $50 in police funds for use in the undercover *821 operation. After recording their serial numbers, she gave two $ 10 bills to Officer Timlick for him to use in a potential undercover buy.
. After Timlick got back in the car, Green repeated to him the lookout she had given. Tim-lick confirmed her description.
. The arrest team seized two $ 10 bills from Gonzalez's hand. Detective Stroud, who was in radio communication with Officer Green, asked Officer Timlick to read from his buy card the last four digits of the serial numbers of the bills he had used in the undercover buy; they matched those on the bills that appellant had in his hand.
The officers also found an additional $21 in Gonzalez's pockеt. Detective Stroud gave this money, along with the $20 seized from Gonzalez's hand, to Officer Milton Norris for processing. Officer Norris put the two pre-recorded $10 bills in one envelope, signed the envelope, sealed it, and gave it to the police department property clerk. The $21 was similarly sealed in a separate envelope and turned over to the property clerk.
. The officers estimated that they were between thirty-five and fifty feet away from Gonzalez at the time of their drive-by identification.
. On cross-examination, dеfense counsel sought to ask Detective Culver whether the money evidence showed signs of tampering, but the court curtailed this line of questioning because Culver had never testified on direct examination that there had been any tampering. What he had said on direct was that the envelope containing the $21 from Gonzalez’s pocket had a seal on it. After being asked by the prosecutor why monetary evidence would be heat-sealed, Culver explained that seals prevent tampering and protect the chain of custody.
. Gоnzalez said that he had been purchasing drugs every day from Carlos for the past four and a half years. On cross-examination, however, he said he did not know Carlos’ last name or where he lived.
. Gonzalez testified that Carlos gave him two $10 bills, not the $20 bill that he had originally given to Carlos.
. A "communication-impaired person” includes a person who does not speak English. D.C.Code § 31-2701(2). A “non-English speaking person” is defined, in turn, as:
a person who is unable to readily understand oral and written communications in the English language or who cannot communicate effectively in the spоken English language. D.C.Code § 31-2701(4). “Appointing authority" is defined to include a judge of any court of the District of Columbia "or any other person presiding at any hearing or other proceeding in which a qualified interpreter is required pursuant to this chapter [the Interpreter Act].” D.C.Code § 31-2701(1).
For a more detailed discussion of the Interpreter Act, see Barrera v. United States, 599 A.2d 1119, 1130-1133 (D.C.1991).
. See also United States v. Huang,
. State court decisions are to the same effect.
See, e.g., People v. Aranda,
. There may, of course, be cases in which difficulties with the interpreter are not known either to the defendant or to counsel until after the trial has ended. In such a case, the defendant could not be accused of remaining silent and wagering on the jury's verdict. That situation, however, is not presented here, and thus we do not address it.
. Gonzalez claims that the competence of the interpreter was also questioned on two other occasions. The portions of the transcript which he cites, however, merely show that the interpreter was having trouble finishing his simultaneous translations when counsel were repeatedly interrupting to make objections.
. We recognize that a distinction can be drawn between a challenge to the competence of a translator during the course of a trial and a claim that the court failed to make a preliminary determination, before trial, of an interpreter's qualifications.
See Kim Long Ko v. United States,
.
See, e.g., State v. Natividad,
.
See, e.g., United States
v.
Mayans,
As the court explained in Joshi:
The Court Interpreters Act, while underscoring the importance of ensuring the highest quality translations for non-English speaking defendants, does not create new constitutional rights for defendants or expand existing constitutional safeguards. Rather, the purpose of the Act is to mandate the appointment of interpreters under certain conditions and to establish statutory guidance for the use of translators in order to ensure that the quality of the translation does not fall below a constitutionally permissible threshold. The basic constitutional inquiry remains unchanged: whether any inadequacy in the interpretation made the trial fundamentally unfair.
. For clarity, we note that the trial court’s discretion to determine the competence of the interpreter refers only to the factual questions of whether an interpreter is needed and whether the appointed interpreter meets the statutory requirements. "[A] trial court does not have discretion to decide whether a defendant who needs an interpreter has a legal entitlement to one."
State v. Gonzalez-Gongora, supra
note 15,
. We note that appellate counsel has not pointed out any other alleged mistranslation at trial.
. For a discussion of the mug shot rule,
see, e.g., Williams v. United States,
. There was no dispute that Gonzalez was the person arrested, i.e., the person depicted in the arrest photograph. The issue before the jury, however, was whether Gonzalez was the person who sold drugs, through an intermediary, to Officer Timlick. Gonzalez did not deny that he was arrested or even that he was involved in an attempted drug transaction with a third person (Carlos); his defense was simply that he was a prospective buyer, not a seller. The photograph was of no help to the jury in deciding whether to accept or reject that defense.