People v. DePallo
Court of Appeals of New York
96 N.Y. 2d 437 (2001)
After DePallo (defendant) admitted his involvement in a murder during pretrial proceedings, his attorney advised him not to testify and, if he did, to testify truthfully; DePallo nonetheless testified falsely at trial that he was home all night, and after both sides rested, his attorney privately told the judge, outside DePallo's and the prosecutor's presence, that DePallo had perjured himself, without otherwise addressing the testimony in closing arguments. DePallo was convicted, and the appellate division rejected his claim that this disclosure denied him effective assistance of counsel; he appealed.
Whether, under state ethics rules, a lawyer may assist or participate in the presentation of a client's perjured testimony.