Kansas v. Ventris

Ventris, charged with murder and aggravated robbery, made incriminating statements to a jailhouse informant the police had planted, and the state conceded this probably violated his Sixth Amendment right to counsel. At trial, Ventris testified and pinned the murder and robbery on his partner instead, so the state sought to introduce his earlier incriminating statements solely to impeach that trial testimony, and the trial court allowed the informant to testify for that purpose; the jury convicted Ventris. The state supreme court reversed, holding that evidence obtained in violation of the Sixth Amendment can never be admitted for any purpose, and the U.S. Supreme Court granted certiorari.