(Reuters) - A federal appeals court on Friday threw out the death sentence for a man forced to wear a “stun belt” during the penalty phase of his trial for a 1996 triple murder in Indiana.

The 7th U.S. Circuit Court of Appeals in Chicago said John Stephenson, 54, was prejudiced by his lawyer’s failure to object to the belt, which lets an officer administer an electric charge to prevent a prisoner from misbehaving in the courtroom.

A box on the belt that contained electric wires had been hidden under Stephenson’s shirt but visible as a bulge to jurors, four of whom had been aware of the belt.

Stephenson had also worn the belt during his eight-month trial, but never acted up.

Though the appeals court upheld Stephenson’s conviction, Circuit Judge Richard Posner said the belt “contaminated” the penalty phase of his trial.

“The fault is certainly not Stephenson’s; it’s his lawyer’s, for failing to object to his client’s having to wear a stun belt, given the absence of any reason to think his client would go berserk in the courtroom,” Posner wrote.

A spokesman for Indiana Attorney General Curtis Hill did not immediately respond to requests for comment. Stephenson’s lawyers did not immediately respond to requests for comment.

The appeals court said Indiana can ask a jury to reimpose the death penalty if Stephenson does not wear the stun belt, or ask a judge to impose a lesser penalty.

Stephenson was convicted of murdering three people inside a pickup truck at a rural intersection in March 1996.

The case is Stephenson v Neal, 7th U.S. Circuit Court of Appeals, No. 16-1312.