Delphi murder suspect Richard Allen reportedly confessed to the brutal 2017 killings of teens Abigail Williams and Liberty German during a series of prison phone calls with his wife — but the defense argued he could be losing his mind behind bars.

“I did it. I killed Abby and Libby,” Allen, 52, said in a phone call played in court Thursday, ABC News reported.

When his wife, Kathy, said he couldn’t have done it, Allen responded “Yes, I did.”

“Why would you say that? I know you didn’t. There’s something wrong,” Kathy reportedly replied.

The conversation was just one of a series of confessions Allen appeared to make to his wife during phone calls from prison — several of which were played to the court.

In each call, Allen insisted he’s guilty, while his wife remained adamant that he’s not.

“I think maybe I’ve lost my mind,” Allen said in another call, adding “I need you to know I did this.”

“No, you haven’t. You’re unwell,” his wife insisted.

In another call, Allen asked whether his wife would stand by him if he was executed for the crimes.

“If I get the electric chair or the death penalty, will you be there for me? I killed Abby and Libby,” he said.

 “I did it, Kathy. I did it. Do you still love me?” Allen said in another call.

“Yes, I do. But you didn’t do it,” she responded.

The victims were just 13 and 14 years old when a man pulled a gun on them as they walked along a train trestle in the woods near their Indiana homes.

One of the girls took out her phone and filmed the man’s approach in now-infamous footage, where their suspected attacker was heard ordering them to go “down the hill.”

During the first week of the trial, jurors were shown graphic photos showing how the girls’ throats had been viscously slashed open during the violent killings.

Despite his confessions — which he also made to prison guards and a psychologist — the court has heard arguments that Allen might be losing his mind after 13 months of solitary confinement and that his claims were false.

One psychologist testified that in her opinion Allen was suffering from “situational psychosis” from his imprisonment and that he was swinging back and forth from lucidity to psychotic episodes, ABC reported.

His behavior during his confinement has been notably alarming.

Allen has been stopped from smashing his head against cell walls, bathing in his toilet, refusing to eat then consuming paper, and covering his face and cell walls in feces, prison guards testified.

“I don’t know what I’m doing. I don’t know if I’ve lost my mind,” he told his wife on one call.

“I feel like I’m already in hell. I don’t understand what’s going on,” he added.