More than 30 years after 19-year-old Colleen Slemmer was tortured, mutilated and murdered in Tennessee, former Knoxville Police Chief Phil Keith says the “satanic” crime scene still haunts him.

“I’ll remember this case to the day I die,” Keith told News Outlet on Thursday. He served as Knoxville’s police chief from 1988 to 2004 and spent decades in law enforcement.

The attack was led by Christa Pike, who was 18 at the time. Pike and three classmates from the Knoxville Job Corps Center, a vocational program for troubled young people, lured Slemmer away by saying they planned to visit a music store and retrieve marijuana they had hidden in a park.

“She represents pure evil,” Keith said of Pike.

Keith said Slemmer endured nearly an hour of torture. Her attackers beat and cut her, gagged her and ultimately crushed her skull against the ground with a piece of broken asphalt.

When Slemmer attempted to flee, the group restrained her. When she pleaded for her life, they cut her with blades. And when she cried out, they used a hair tie to gag her. Pike, now 50, allegedly kept a piece of Slemmer’s skull as a trophy and displayed it to classmates before her arrest. Pike’s boyfriend, who was also convicted, carved pentagrams into Slemmer’s chest and face. Because he was 17 at the time, he was not eligible for the death penalty.

A trial expert testified that the killing contained “satanic elements” and reflected “the phenomenon of collective aggression,” in which a group becomes emotionally charged and ultimately engages in “some kind of violent, extremely violent activity,” according to court records.

The University of Tennessee groundskeeper who discovered Slemmer’s remains testified that he first believed he had found an animal carcass. He realized otherwise only after seeing the victim’s clothing amid the blood, court records show.

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“The images are as vivid today as the day I saw them,” Keith said. “All I have to do is shut my eyes, and I can see everything.”

Thirty-one years later, Keith said he wishes the Knoxville Police Department had offered modern trauma counseling to officers who handled the case.

“We didn’t have therapy services or counseling or anything at that time, and I wish we had, because these images will never be erased,” Keith said.

Pike was scheduled to be executed Wednesday. The U.S. Sixth Circuit Court of Appeals issued a brief stay after a last-minute appeal, but the Supreme Court lifted it, clearing the way for the lethal injection.

After two doses of the execution drug, Pike remained alive. She was taken to an undisclosed hospital Thursday in critical condition for “lifesaving care,” according to her attorneys. On Friday, they said she was unconscious and on a ventilator.

“Christa remains critically ill and is receiving medical care for the devastating effects of Wednesday night’s events,” attorneys Stephen Ferrell and Luke Ihnen said in a statement Friday. “As detailed in today’s filing, Christa remains hospitalized following Wednesday night’s failed execution attempt.

“She is critically ill, unconscious, intubated and receiving breathing assistance through a ventilator,” they said. “She is being treated for the serious effects of the pentobarbital administered during the execution attempt, including significant injuries to both arms.”

It remained unclear what would happen to Pike next.

During a news briefing Thursday, one of Pike’s attorneys, Randy Spivey, said Slemmer’s mother had been on Pike’s mind in the hours before the scheduled execution.

“I cannot imagine what this was like for the family of Ms. Slemmer, or anyone who loves that family or is close to that family — or anyone who loves Christa or is close to Christa,” he said. “This is awful, and this kind of thing should never happen again.”