Joseph Sapia was convicted after a jury trial of criminally selling a dangerous drug in the first degree and criminally selling a dangerous drug in the third degree. The charges arose from two separate transactions: one on June 27, 1973, resulting in the sale by defendant of four ounces of heroin, and the second taking place on July 6, 1973, resulting in the sale by defendant of one kilo of heroin.
The sales were made to an undercover police officer who was closely monitored by his backup team. The closely coordinated police work included the taking of tape recordings and videotaping, which resulted in the submission for the consideration of the jury of a case overwhelmingly proving the guilty participation of the defendant.
*526Defendant, however, urges that he was prejudiced in the presentation of his case by his inability to call an undercover informant to testify, which inability constitutes reversible error.
The initial contact by undercover Police Officer Hayward was made through Earl Fodderell, who was known to the police as a major narcotics dealer. Fodderell, already under Federal indictment, acted as an agent of the police and arranged for Hayward to meet one Robert Gardner, who ultimately arranged for the meeting with Sapia.
Fodderell’s only other connection with the case, as presented to the jury, was his making a telephone call to the defendant to arrange for a new meeting. This was because the initial four-ounce sale was scheduled to be made on June 26. When that meeting was aborted due to defendánt’s failure to appear on time, a new meeting had to be arranged.
Fodderell, who was in a Federal prison at the time of this trial, had been brought to court as a potential defense witness. He was interviewed in chambers by the Trial Justice without the presence of defense counsel or the District Attorney. The court then expressed its opinion that Fodderell’s testimony might be beneficial to the defense. However, Fodderell, who had already been sentenced in Federal court to a 12-year term of imprisonment and had an additional Federal indictment pending, declined to testify unless granted immunity, which immunity the District Attorney refused to confer.
The court then informed the jury that Fodderell was available but that he refused to testify, claiming his constitutional right to remain silent.
Defense counsel attempted to introduce alleged exculpatory statements tending to show a defense of entrapment via an interview held between defendant and his attorney. That interview took place after the narcotics sale but before the arrest. The court properly denied the admissibility of those statements since they clearly were self-serving.
My dissenting brother finds it questionable whether Fodderell can claim Fifth Amendment immunity and, furthermore, whether the failure of the District Attorney to confer immunity warrants reversal of the conviction.
It is to be noted that an agent of a governmental authority, when questioned about occurrences related to his official duty, has the right to claim his Fifth Amendment privilege (Gard*527ner v Broderick, 392 US 273; Spevack v Klein, 385 US 511; Malloy v Hogan, 378 US 1). The right to assert this privilege is, as Mr. Justice Brennan stated in Malloy v Hogan (378 US 1, 8): "[T]he right of a person to remain silent unless he chooses to speak in the unfettered exercise of his own will, and to suffer no penalty * * * for such silence.”
A penalty in the context of that statement means imposition of any sanction which makes assertions of the Fifth Amendment privileges "costly” (Spevack v Klein, 385 US 511, 515). Therefore, in the context of the case at bar, Fodderell, though acting as an informer for the police, did not lose his right to claim his Fifth Amendment privilege. Indeed, two immediate reasons for his invoking the privilege come to mind: It is possible that, while Fodderell was performing his duties on behalf of the police, he at the same time, and intertwined in the same transaction, performed acts which were of a criminal nature and which were unauthorized to be performed. He has a right to protect himself against prosecution because of his performance of those acts. In addition, Fodderell had already testified in Federal court regarding this transaction. Defense counsel conceded on the record that the testimony Fodderell would give at the trial was substantially different from the testimony already given in Federal court. He would therefore be exposing himself to a possible perjury indictment which even a grant of transactional immunity, requested by the District Attorney and conferred by the court, could not prevent (CPL 50.30; 50.10, subd 1).
However, the mere right of a witness to assert his Fifth Amendment privilege does not reach the question as to whether defendant was able nonetheless to get a fair trial. We have nothing in the record other than conjecture as to what testimony Fodderell would give had he been granted immunity.
The court, after an in camera interview alone with Fodderell, stated: "As to what the testimony would be, I think it would be a fair summary that if believed by the jury, would be exculpatory. Whether or not the testimony would be completely exculpatory if believed by the jury, is by no means clear to me at this point. I am not at all clear the attorneys who have spoken to him, his attorneys, have a sufficiently detailed understanding of all the aspects of it, lead me to form an opinion on that, but there is no question at all it would, at *528least in part, be exculpatory, would be material evidence in the case, and evidence that a jury ought to hear.”
The court later stated: "I’m not persuaded that if every word he were to say would be believed, it would constitute a complete defense in the case, nor as a factual matter, would avoid a conviction, but it might.”
Clearly, the court felt that further probing by defense counsel would reveal the true value of Fodderell’s testimony. Such probing by defense counsel took place and they found his statements at the interview to be "wholly inconsistent” with statements he made to the Federal Government.
The defense made no offer of proof which would have clearly delineated the parameters of the testimony to be elicited from Fodderell and would have indicated whether or not there could be an evidentiary articulation of the defense of entrapment.
Despite the fact that the prosecution requested defense counsel to make an offer of proof, none was forthcoming. The court’s estimate of the exculpatory nature of the testimony was, as stated by the court, subject to in-depth interview by counsel with greater knowledge of the background facts. Counsel conceded that the gross inconsistency between Fodderell’s proposed testimony at trial (which proposed testimony they did not outline) and the statement given in Federal court could well subject Fodderell to a perjury indictment and, on that basis, they rejected calling him unless he were granted immunity.
In view of the overwhelming evidence against defendant and in view of the conjectural nature of the missing testimony, we cannot hold that the failure to grant immunity constituted reversible error.
This is especially true since there was no affirmative duty upon the prosecution to call Fodderell as a witness. He did not. participate in the sale itself, nor did he act to identify the defendant (cf. People v Goggins, 34 NY2d 163). The People’s duty was fulfilled when Fodderell’s identity was made known and he was made physically available to the defense (United States v La Couture, 495 F2d 1237, cert den 419 US 1053; People v Goggins, supra).
The District Attorney expressed no knowledge of exculpatory statements and, absent an offer of proof, could not formulate their validity or for that matter their existence. Absent *529knowledge of specific exculpatory material or a specific source of such material, the People have no duty to grant immunity based on speculation and conjecture as a pseudo-fulfillment of the rule prohibiting suppression of "evidence favorable to an accused” (cf. Brady v Maryland, 373 US 83, 87).
Accordingly, the judgment of the Supreme Court, New York County, convicting the defendant after jury trial of the crimes of criminal sale of a dangerous drug in the first degree and criminal sale of a dangerous drug in the third degree, should be affirmed.