The opinion of the court was delivered by: Smith, J.:
This opinion is uncorrected and subject to revision before publication in the New York Reports.
The lawyer who represented defendant at a pre-trial hearing and at trial was simultaneously representing, in an unrelated matter, a police officer who testified for the People that defendant had confessed to one of the charged crimes. We hold that, because there was no valid waiver of the lawyer's conflict of interest, defendant is entitled to a new trial.
Defendant was charged with raping his daughter, and committing other sex offenses against her, over a four year period beginning when she was 10 years old. The evidence against him included a partial confession, in which defendant told two police detectives, Karen Smith and Larry Kuebler, that he had had sex with his daughter once.
A Huntley hearing was held on the voluntariness of defendant's statements to the detectives. Before the hearing began, defense counsel advised the court that she represented Kuebler "in an unrelated civil matter." She said that she had disclosed this to defendant, and that defendant "respects the nature of my representation of Detective Kuebler . . . and . . . has agreed to waive any conflict in that regard." The judge asked defendant: "Is that correct, Mr. Solomon?" and defendant replied "Yes, sir." The record reflects no other discussion with defendant about the conflict, and discloses nothing further about the nature of counsel's representation of Kuebler.
Kuebler testified at the Huntley hearing and at trial, and was cross-examined by the lawyer who was representing him. According to Kuebler's testimony (which was consistent with Smith's), Smith was the detective in charge of the case and had been the first to interview defendant, while Kuebler sat in a nearby room, listening through an audio system and taking notes.
He testified that defendant first denied to Smith that he had sex with his daughter, but that as the interview went on "his denials kind of weakened . . . [a]nd at one point Detective Smith asked him if he did have sex with his daughter and he stated that he did." After Smith finished her interview, Kuebler conducted his own, in which, Kuebler testified, defendant told Kuebler "that he got drunk one time and had sex with his daughter just one time."
Defendant's motion to suppress his statements was denied, and he was convicted by a jury. He appealed on the ground, among others, that his lawyer's conflict denied him the effective assistance of counsel. The Appellate Division agreed with defendant that the trial court's inquiry into the conflict was insufficient, and that defendant's waiver was therefore invalid. It nevertheless affirmed, holding that defendant "failed to establish that any 'conflict affected the conduct of the defense'" (People v Solomon, 73 AD3d 1440, 1441 [4th Dept 2010], quoting People v Ortiz, 76 NY2d 652, 657 ). A Judge of this Court granted leave to appeal (17 NY3d 801 ), and we now reverse.
We agree with the Appellate Division that defendant did not effectively waive any conflict of interest here -- indeed, the People do not strongly argue otherwise. Our cases make clear that a defendant in a criminal case may waive an attorney's conflict, but only after an inquiry has shown that the defendant "has an awareness of the potential risks involved in that course and has knowingly chosen it" (People v Gomberg, 38 NY2d 307, 313-314 ; see also People v Macerola, 47 NY2d 257, 263 ; People v Wandell, 75 NY2d 951, 952-953 ). The inquiry here, in which not even the nature of defense counsel's simultaneous representation of Kuebler was placed on the record, was simply inadequate.
Thus, the case turns on whether the conflict had such a "substantial relation to the conduct of the defense" as to require reversal (People v McDonald, 68 NY2d 1, 9  [internal quotation marks and citation omitted]). We conclude that it did.
Discussions of the effect of a lawyer's conflict of interest on a defendant's right to the effective assistance of counsel distinguish between a potential conflict and an actual conflict (e.g., Cuyler v Sullivan, 446 US 335, 337, 349-350 ; People v Macerola, 47 NY2d 257, 264-265 ). The distinction can be illustrated by cases in which, as in Cuyler and Macerola, the same lawyer represents more than one defendant. Such a multiple representation carries the potential for conflict, but the potential will not always be realized. In some cases, the interests of co-defendants will be in harmony, as for example when their defense consists of an attempt to show that prosecution witnesses are lying or mistaken. Thus, in Macerola, we rejected a per se rule that simultaneous representation of co-defendants automatically requires reversal in the absence of a valid waiver:
"There may always exist those cases in which joint representation of multiple defendants is, without doubt, justified, and the court's neglect in admonishing co-defendants of the potential risks entailed in joint representation would not deprive, without more, a defendant of his right to the effective assistance of counsel" (47 NY2d at 264).
Similarly, in Cuyler, the Supreme Court, though observing that "a possible conflict inheres in almost every instance of multiple representation" (446 US at 348), held that the mere "possibility of conflict is ...