A unanimous U.S. Supreme Court on Wednesday ruled that prosecutors may use evidence from a court-ordered mental evaluation against a capital defendant to rebut the defendant’s own psychiatric testimony.

Justice Sonia Sotomayor, writing for the court in Kansas v. Cheever, reaffirmed Buchanan v. Kentucky, a 1987 ruling that allowed prosecutors to use that evidence for the limited purpose of rebutting a “mental-status” defense.

“The state permissibly followed where the defense led,” Sotomayor wrote. “Excluding this testimony would have undermined Buchanan and the core truth-seeking function of the trial.”

The court sent the case back to Kansas courts, where lawyers for convicted murderer Scott Cheever will still be able to make a constitutional argument that the prosecutors’ use of the disputed testimony exceeded the scope permitted under the Fifth Amendment.

Cheever’s lawyer, Neal Katyal, declined to comment until he could speak with his client. Katyal, the former acting U.S. solicitor general, is a partner at Hogan Lovells, where he took on the Cheever matter—his first death penalty case—on a pro bono basis.

Kent Scheidegger, legal director of the Criminal Justice Legal Foundation, applauded the Supreme Court ruling. “If the defendant chooses to open the door with his own psychological expert, this evidence must be available to both sides,” Scheidegger said.

Cheever shot and killed a Greenwood County sheriff in 2005 while high on methamphetamines. He was charged with murder, and the case was tried at first in federal court during a period when the Kansas death penalty had been found unconstitutional.

Lawyers for Cheever notified the court they would introduce evidence that his drug use left him unable to “form specific intent” to commit murder. Under Rule 12 of the Federal Rule of Criminal Procedure, the judge ordered a psychiatric evaluation of Cheever, which determined that he shot the sheriff because of his “antisocial personality,” not his drug use.

The case ultimately returned to state court, where Cheever’s lawyers presented expert testimony that his drug use had damaged his brain and influenced his actions on the day of the murder. The state tried to introduce the court-ordered examination, but the defense objected, claiming that because the exam was not voluntary, using it at trial would violate Cheever’s Fifth Amendment right not to be compelled to incriminate himself. The trial judge allowed the testimony and Cheever was found guilty and sentenced to death.

But on appeal, the Kansas Supreme Court ruled for Cheever, finding he had not waived his Fifth Amendment rights by submitting to the court-ordered examination. It also ruled that under Kansas law, voluntary intoxication was not a mental-state defense that would trigger the state’s right to rebut Cheever’s expert testimony.

Sotomayor said that was too narrow a reading of the high court’s precedents, and that preventing the state from using the earlier interview at trial would “undermine the adversarial process, allowing a defendant to provide the jury, through an expert operating as proxy, with a one-sided and potentially inaccurate view of his mental state at the time of the alleged crime.”

The ruling does leave one potential defense open for Cheever on remand, on whether the state’s actual use of the court-ordered examination went beyond the “limited rebuttal purpose” allowed under Buchanan. Since the Kansas Supreme Court did not rule on that point, Sotomayor said the issue should be left to state courts.

Contact Tony Mauro at tmauro@alm.com.