An Allegheny County Common Pleas judge granted a mistrial Wednesday in the case of a man accused of killing his girlfriend’s ex during a custody exchange in Pittsburgh three years ago.

Ambrose Sample Jr., 45, is charged with killing Corey Washington in the Family Dollar parking lot on Brighton Road on Dec. 26, 2022.

During testimony on Wednesday, a Pittsburgh police officer inadvertently revealed to the jury that Sample had a previous homicide on his record. The officer referenced a conversation in which Sample said he’d “caught another body.”

Defense attorney Ryan Tutera requested a mistrial, and Judge Bruce Beemer granted the request.

Sample has a previous conviction from 1999 for third-degree murder in Westmoreland County. In that case, he was found guilty for killing Phillip Williams in Arnold with a shotgun.

Sample was ordered to serve 12 to 25 years in state prison. He was paroled on July 25, 2016.

While out on state parole in June 2017, Sample was charged by the U.S. Attorney’s Office in federal court with being a felon in possession of ammunition after Pittsburgh police said he pulled a firearm from his waistband and fired into the air after a dispute with neighbors.

Sample was found guilty following a bench trial in that case and in July 2019 was ordered to serve 4½ years in federal prison to be followed by three years of supervised release.

Sample was released from federal prison on Jan. 25, 2022.

He was arrested in the current homicide case less than a year later.

During opening statements on Monday, Sample’s attorney told the jury that his client was acting that day to defend his girlfriend after she had been attacked.

According to trial testimony, Washington had driven to the Family Dollar Parking lot that afternoon to exchange custody of his 4-year-old son with the boy’s mother, Tanisha Turner.

Washington and Turner began arguing, she testified Tuesday, when Washington struck her in the face.

After at least one more strike, Washington’s sister attacked Turner and started beating her in the parking lot.

In the meantime, police said, Sample, who had been waiting in the car, got out and fired at least three shots, killing Washington.

Video surveillance cameras from a nearby library captured the incident.

Sample is also accused of threatening Washington’s sister with the gun.

Prosecutors had about a half dozen witnesses to go in the case when Beemer granted the mistrial request.

“I have to protect my client at all times,” said Tutera, Sample’s attorney.

Prior to the start of trial, Tutera said he had filed motions to prevent his client’s previous criminal history from being referenced at all in the case.

“That whole sequence of events doesn’t need to be addressed,” Tutera said. But now, “here we are with the exact issue I was concerned about.”