Defendant was convicted of illegal importation and possession of a controlled substance with intent to distribute. At trial he denied any knowledge that the heroin was in the car. On appeal, he claims primarily that his due process rights were violated by the prosecutor’s use of post-arrest silence to impeach his trial testimony. We affirm.
I. Post-Arrest Silence
On December 15, 1980, defendant drove into the San Ysidro Port of Entry. Responding to the customs inspector’s questions, he said he had visited Mexico for fun and had been there for two or three hours. He said that the car belonged to a friend.
The heroin was discovered following inspection in the secondary inspection area, to which the customs inspector had directed him. He was arrested and advised of his rights. Upon questioning by Drug Enforcement Administration special agent Murray, he claimed he knew nothing of the heroin. He told the agent that the car belonged to a white man, a “gabacho,” that he had driven into Mexico that morning, and that his purpose was to visit a friend. Although he first claimed not to know the identity of the car’s owner, he later explained that he borrowed the car from his friend, who was a friend of the owner.
Agent Murray’s first question about the identity of the friend from whom defendant borrowed the car was unanswered. But defendant later identified the friend as Angel Ortega. Responding to questioning designed to discover where Ortega could be found, defendant told the agent that he lived in an apartment complex in Santa Ana. Although he asserted that he did not know the street address, he revealed the name of the street and the apartment number of Ortega’s residence. He did not know the telephone number.
Defendant testified at trial.1 Claiming that defendant’s trial testimony was *1285inconsistent with his statements at the time of arrest, the prosecutor conducted the following cross-examination of the defendant:
BY PROSECUTING ATTORNEY:
Q. [Y]ou didn’t tell Agent Murray, did you, that you had been set up by Jose Angel Ortega?
A. Because he didn’t let me speak. He told me, “You have a right to remain silent. Don’t speak.” That’s why I didn’t speak.
Q. Well, he asked you where Jose Angel Ortego lived, didn’t he?
A. Yes.
Q. And you didn’t tell Agent Murray, did you, that, “I just left a bar in Tijuana with the owner of this car”?
A. Because he didn’t let me explain everything to him.
Q. So you mean there was no opportunity for you to tell Agent Murray where you had been before coming to the Port of Entry?
A. No.
Q. There was no opportunity for you to tell Agent Murray where you had come from?
A. He didn’t let me speak.
Q. But he let you tell him the address of Jose Angel Ortega, didn’t he?
A. I told him where he could find him.
Q. And you said an address in Santa Ana, didn’t you?
A. Yes.
Q. But you didn’t tell him that you had just been with Mr. Jose Angel Ortega a half — a short time before you were arrested; you didn’t tell him that, did you?
A. Because he told me to be quiet.
Q. Now, you also told Agent Murray, didn’t you, that you had left Santa Ana and had come to Tijuana to see a friend or have some fun, didn’t you?
A. He didn’t understand me. I told him with a friend.
Q. So you had time to tell him you had come with a friend, didn’t you? You had an opportunity to tell him that, didn’t you?
A. Because he asked me.
Q. During the entire time that you were being questioned by the agent, you never told them [sic ] that you could lead them to Jose Angel Ortega right then, did you?
A. No, because he asked me, “Who is the owner of the car,” and I told him.
Q. And you didn’t tell him where he was right at that minute, did you?
A. I told him where he lived.
*1286Q. And you didn’t tell him where he was right then, did you? You didn’t tell him that he was in a bar in Tijuana right then, did you?
A. No. It’s that he didn’t let me speak. He told me, “You have the right to remain silent and be quiet.” So I remained silent
If defendant had invoked his right to remain silent in response to Miranda warnings, questioning that asked why certain information had not been revealed would have been improper. Doyle v. Ohio, 426 U.S. 610, 96 S.Ct. 2240, 49 L.Ed.2d 91 (1976); United States v. Hale, 422 U.S. 171, 95 S.Ct. 2133, 45 L.Ed.2d 99 (1975); Bradford v. Stone, 594 F.2d 1294 (9th Cir. 1979) (per curiam).
The Supreme Court, in Hale and Doyle, held that due process prohibits impeaching a defendant’s testimony at trial by using his silence following Miranda warnings. In these cases, the defendants had elected to remain silent and said nothing to the officers who attempted to interrogate them. The Court noted that “[sjilence in the wake of these warnings may be nothing more than the arrestee’s exercise of these Miranda rights.” Doyle v. Ohio, 426 U.S. at 617, 96 S.Ct. at 2244.
Ochoa-Sanchez did not remain silent in response to Miranda warnings. He waived his right to remain silent and responded to the agent’s questions. In such a situation, we believe the controlling authority to be Anderson v. Charles, 447 U.S. 404, 100 S.Ct. 2180, 65 L.Ed.2d 222 (1980), in which the Court distinguished Doyle as follows:
But Doyle does not apply to cross-examination that merely inquires into prior inconsistent statements. Such questioning makes no unfair use of silence, because a defendant who voluntarily speaks after receiving Miranda warnings has not been induced to remain silent. As to the subject matter of his statements, the defendant has not remained silent at all.
Id. at 408, 100 S.Ct. at 2182.
In Charles the Court held permissible cross-examination about prior inconsistent statements. The prosecutor several times asked the defendant why he did not reveal to the police the version of events to which he testified at trial. The questions, taken as a whole, did not focus on the defendant’s exercise of the right to remain silent, but instead focused on why he had failed to tell the police he took the victim’s car from a parking lot, as he testified at trial, rather than from the street as he stated upon his arrest. Id. at 408-09, 100 S.Ct. at 2182.
In Grieco v. Hall, 641 F.2d 1029 (1st Cir. 1981), the First Circuit accurately construed the Charles case. It wrote:
[Ojnce a defendant makes post-arrest statements that may arguably be inconsistent with the trial story, inquiry into what was not said at arrest may be designed not “to draw meaning from silence, but to elicit an explanation for a prior inconsistent statement .... Each of two inconsistent descriptions of events may be said to involve ‘silence’ insofar as it omits facts included in the other version. But Doyle does not require any such formalistic understanding of silence . . . . ”
Id. at 1034 (quoting Anderson v. Charles, 447 U.S. at 409, 100 S.Ct. at 2182).
When the defendant offers testimony at trial that differs from his post-arrest statement, he raises a question of credibility. The jury must determine whether to believe the version of events to which the defendant testifies at trial or the version he revealed to the police when arrested. In such a situation, the jury is entitled to all the relevant evidence bearing on credibility. The prosecutor, to provide this evidence, may probe all post-arrest statements and the surrounding circumstances under which they were made, including defendant’s failure to provide critical details. See Lofton v. Wainwright, 620 F.2d 74, 78-79 (5th Cir. 1980).
The trial transcript reveals that defendant’s version of the events of his trip into and return from Mexico is quite different from the version he proposed to agent Murray upon his arrest. When he was arrested he claimed that he had borrowed the car *1287from a friend who lived in Santa Ana, that he had driven to Tijuana to visit a friend, and that he was returning. At trial, he asserted that he had hesitatingly accompanied two specific acquaintances to a bar in Tijuana and had assumed control of the car only a short time before. Several other portions of his trial testimony arguably are inconsistent with his post-arrest statements, but they need not be described in detail. It is sufficient if the statements, taken as a whole, reveal an inconsistency. See Anderson v. Charles, 447 U.S. at 408-09, 100 S.Ct. at 2182.
Moreover, we do not believe the prosecutor was .attempting to draw meaning from the defendant’s silence. The questioning clearly related specifically to details that defendant offered at trial but failed to reveal at the time of his arrest. As in Charles, the questions, by focusing on agent Murray’s testimony, resolved any potential ambiguity. “The questions were not designed to draw meaning from silence, but to elicit an explanation for a prior inconsistent statement.” Id. at 409, 100 S.Ct. at 2182.
For these reasons, we hold that defendant’s due process rights were not violated by the prosecutor’s cross-examination. Our resolution of his contention regarding the cross-examination also precludes defendant’s success on his other claims. He asserts similar arguments about the prosecutor’s direct examination of agent Murray and his closing argument.
Because defendant’s trial testimony raised an issue of credibility, which opened to the prosecutor the circumstances of his post-arrest statement, the prosecutor’s examination of agent Murray2 properly revealed the limits of defendant’s statement at time of arrest. Similarly, the prosecutor argued vigorously in closing argument about the credibility of defendant’s trial testimony,3 but stopped short of inviting a conviction from his silence.
*1288II. The Defense Subpoena
On the morning of the trial, the district court quashed a defense subpoena that requested all information about all past cases in which a prosecution witness, an informant, had provided information to the police. The judge refused an in camera inspection and refused to seal the records for appellate review. The defendant claims a Sixth Amendment violation.
The government offered testimony that the informant began providing information about the defendant about a month after the defendant’s arrest and that he was not paid for the information. The witness revealed that the informant had worked for the police department for a year, receiving about $500 for his services.
The defendant fails to identify any potentially relevant use for the files and acknowledges that the request was designed to “determine what materials could be used to impeach the witness.” The court properly quashed the subpoena because the files were irrelevant and disclosure could destroy their confidentiality. See United States v. MacKey, 647 F.2d 898, 901 (9th Cir. 1981); United States v. McGrady, 508 F.2d 13, 18 (8th Cir. 1974), cert. denied, 420 U.S. 979, 95 S.Ct. 1408, 43 L.Ed.2d 661 (1975). Moreover, by asking for all information in all cases, the subpoena was overbroad. United States v. Wencke, 604 F.2d 607, 612 (9th Cir. 1979).
The cases cited by defendant are inapposite. They relate to situations in which, without the requested information, the defense was completely unable to cross-examine a government witness about potentially impeaching events and circumstances. See, e.g., Davis v. Alaska, 415 U.S. 308, 94 S.Ct. 1105, 39 L.Ed.2d 347 (1974); Smith v. Illinois, 390 U.S. 129, 88 S.Ct. 748, 19 L.Ed.2d 956 (1968); United States v. Alvarez-Lopez, 559 F.2d 1155 (9th Cir. 1977). In contrast, defendant conducted a meaningful cross-examination using impeaching information that the witness was an informant and had assisted the government in other cases.
The trial court acts in its discretion in deciding whether to quash a subpoena. United States v. Nixon, 418 U.S. 683, 94 S.Ct. 3090, 41 L.Ed.2d 1039 (1974). Presumably, in camera inspection of the files and sealing them for appellate review would have been the preferable practice. But the court’s failure to do so is not fatal. See United States v. Lyons, 567 F.2d 777, 783 (8th Cir. 1977), cert. denied, 435 U.S. 918, 98 S.Ct. 1476, 55 L.Ed.2d 510 (1978).
*1289III. Addict-Witness Instruction
The defendant claims error in the trial court’s refusal to instruct the jury concerning its evaluation of testimony of an addict.
The informant testified that he had been addicted to heroin, but that he last had used the drug four weeks before trial. The defense counsel adequately cross-examined about the drug use and directed him to reveal to the jury his arms, which contained needle marks.
An addict instruction is appropriate when a witness is a heroin addict, People of the Territory of Guam v. Dela Rosa, 644 F.2d 1257, 1261 (9th Cir. 1980); United States v. Bernard, 625 F.2d 854, 858 (9th Cir. 1980), but is unnecessary in several situations, including: (1) when the addiction is disputed, United States v. Gregorio, 497 F.2d 1253, 1262 (4th Cir.), cert. denied, 419 U.S. 1024, 95 S.Ct. 501, 42 L.Ed.2d 298 (1974); when the defense adequately cross-examines the witness about the addiction, United States v. Cook, 608 F.2d 1175, 1182 (9th Cir. 1979), cert. denied, 444 U.S. 1034, 100 S.Ct. 706, 62 L.Ed.2d 760 (1980); and (3) when another cautionary instruction is given, United States v. Tousant, 619 F.2d 810, 812 (9th Cir. 1980). See generally United States v. Hoppe, 645 F.2d 630, 633 (8th Cir.), cert. denied, - U.S. -, 102 S.Ct. 170, 70 L.Ed.2d 138 (1981).
At trial in this case, present addiction was not established, the defense conducted a vigorous cross-examination, and the judge gave other cautionary instructions. The court did not abuse its discretion in refusing the requested instruction. See United States v. Cook, 608 F.2d 1175, 1182 (9th Cir. 1979), cert. denied, 444 U.S. 1034, 100 S.Ct. 706, 62 L.Ed.2d 760 (1980).
IV. Prosecutorial Misconduct
The government attempted to elicit from defendant’s former attorney that he withdrew from the case because he believed the defendant would lie on the stand. The government acknowledges the attempt.
Although the defendant probably is correct in asserting that the question was improper, the court did not abuse its discretion in refusing to grant a mistrial. Prosecutorial misconduct must be evaluated in the context of the entire trial. It justifies reversal only when it denies the defendant a fair trial. United States v. Ford, 632 F.2d 1354, 1381 (9th Cir. 1980), cert. denied, 450 U.S. 934, 101 S.Ct. 1399, 67 L.Ed.2d 369 (1981).
The improper question was an isolated incident in a trial lasting several days. The answer was favorable to the defendant, and defendant makes no assertion that the question was offered in bad faith. He fails to identify any prejudice.
In such a posture, any misconduct that did occur does not require reversal. See United States v. Tham, 665 F.2d 855, 860 (9th Cir. 1981); United States v. Berry, 627 F.2d 193, 196-97 (9th Cir. 1980), cert. denied, 449 U.S. 1113, 101 S.Ct. 925, 66 L.Ed.2d 843 (1981).
CONCLUSION
The prosecutor commenced this case with ample evidence. A conservative trial strategy would have resulted in a conviction, presenting the defendant with none of the difficult issues he has raised for our consideration. Instead, the prosecutor engaged in overkill. Nevertheless, defendant received a fair trial, and none of his rights were violated.
The convictions are AFFIRMED.