As digital forensics experts analyzed the cellphone of Bryan Kohberger, the 30-year-old failed criminologist turned convicted murderer, they drew similarities between him and the fictional main character of the book and movie, “American Psycho,” the narcissistic banker Patrick Bateman – and they discovered that he spent Christmas night a month after the slayings reading dozens of articles about serial killers.

“I watched ‘American Psycho’ back in the day, and how vain he was, where he would always take like naked photos of himself flexing, similar to that, like with him just in pants, but topless from the waist up, flexing [in] a mirror forward, backward, making different expressions, but just for himself,” said Heather Barnhart, the senior director of forensics research with the internationally known digital investigations firm, Cellebrite. “It was like he admired his body.”

Her husband, Jared Barnhart, a former Maryland police officer who also works at Cellebrite, also worked the case.

A watchman parked outside 1122 King Road on Dec. 11, 2022, four weeks after four students were stabbed to death inside. The house has since been demolished, and Bryan Kohberger pleaded guilty to the slayings. (Michael Ruiz/Fox News Digital)

His search history included searches for the term “psychopath,” which his lawyers didn’t want used at trial, and about serial killers. Prior to his arrest but after reading a news report about how police had identified a white Hyundai Elantra as the suspect vehicle in the student murders, Kohberger appeared to panic and searched auto detailers and for a replacement car, according to the Barnharts. He also spent a lot of time streaming videos on YouTube and TikTok, they said.

“On his PC [personal computer], ‘psychopath’ was a normal word that he typed into a browser, but he could have said it was for his major or research,” Heather Barnhart told Fox News Digital.

However, he cleared his browsing history for roughly a month leading up to the murders, from Oct. 12, 2022 to Nov. 16.

Bryan Kohberger is seen in a selfie that was taken on Dec. 28, 2022. (Dateline)

He carried out the slayings on Nov. 13, in a 4 a.m. home invasion attack, stabbing all four victims repeatedly. They were Madison Mogen, 21, Kaylee Goncalves, 21, Xana Kernodle, 20, and Ethan Chapin, 20. All but Kernodle are believed to have been asleep at the start of the attack.

Kohberger pleaded guilty to four counts of first-degree murder and one of felony burglary last month. He received four consecutive sentences of life with no parole, plus another 10 years. The plea deal required him to waive his right to appeal and his right to seek a sentence reduction.

While Kohberger is being held in isolation at the Idaho Maximum Security Institute, a state prison near Boise, he is already reportedly the target of harassment and mockery from fellow inmates.