[5] Prosecutors have said that Alcala "toyed" with his victims, strangling them until they lost consciousness then waiting until they revived, sometimes repeating this process several times before finally killing them.

In 1964, after what was described as a nervous breakdown—during which he went AWOL and hitchhiked from Fort Bragg, North Carolina, to his mother's house in California—Alcala was diagnosed with antisocial personality disorder,[13] and estimated to have an IQ of 135 by a military psychiatrist.

[5] On September 25, 1968, a passing motorist named Donald Haines called police after witnessing Alcala lure Tali Shapiro, aged eight, into his Hollywood apartment.

Shapiro, who was residing at the Chateau Marmont with her family, was approached by Alcala on her way to school when he pulled up beside her in his car and asked if she needed a ride.

When the police arrived, Shapiro was found alive in a pool of her own blood, having been raped and beaten with a steel bar; Alcala had fled.

To evade the arrest warrant stemming from the Shapiro assault, Alcala left California and enrolled at NYU, using the name "John Berger.

"[16] Cornelia Crilley, a 23-year-old Trans World Airlines flight attendant, was found raped and murdered in her Manhattan apartment on June 12, 1971.

[24] After Alcala's second release in 1977, his Los Angeles parole officer made the unusual choice of permitting a repeat offender— and known flight risk — to travel to New York City.

Her remains were discovered in 1978 buried under heavy rocks on a hillside overlooking the Hudson River, near a location on the John D. Rockefeller Estate where an aspiring model would later report that "Berger" had taken photos of her.

[26] In 1977, Alcala worked briefly at the Los Angeles Times as a typesetter, and was interviewed by members of the Hillside Strangler task force as part of their investigation of known sex offenders.

[38][39] That decision was upheld in 2003 by a Ninth Circuit Court of Appeals panel, in part because a witness was not allowed to support Alcala's contention that the park ranger who found Samsoe's body had been "hypnotized by police investigators".

[40][14] While preparing for their third prosecution in 2003, Orange County investigators learned that Alcala's DNA, sampled under a new state law[41] over his objections, matched semen left at the rape-murder scenes of two women in Los Angeles.

[14] During his incarceration between the second and third trials, Alcala wrote and self-published a book, You, the Jury, in which he claimed innocence in the Samsoe case and suggested a different suspect.

[44] He took the stand in his own defense, and for five hours played the roles of both interrogator and witness, asking himself questions and addressing himself as "Mr. Alcala" in a deeper-than-normal voice, followed by answering them.

[43] During this self-questioning and answering session, he told jurors, often in a rambling monotone, that he was at Knott's Berry Farm applying for a job as a photographer at the time Samsoe was kidnapped.

[32] He showed the jury a portion of his 1978 appearance on The Dating Game in an attempt to prove that the earrings found in his Seattle locker were his, not Samsoe's.

[45] Jed Mills, the actor who competed against Alcala on the show, told a reporter that earrings were not yet a socially acceptable accoutrement for men in 1978.

[9] As part of his closing argument, he played the Arlo Guthrie song "Alice's Restaurant", in which the protagonist tells a psychiatrist that he wants to "kill".

[51] In December 2012, he changed both pleas to guilty, citing a desire to return to California to pursue appeals of his death penalty conviction.

[55] In the first few weeks, police reported that approximately 21 women had come forward to identify themselves,[56][57] and "at least six families" said they believed they recognized loved ones who "disappeared years ago and were never found".

[60] Rowan claimed that while she was living in Hollywood, she was approached by Alcala at a teen nightclub on the Sunset Strip and entered his car believing he would be driving to an IHOP restaurant.

[62] In March 2011, investigators in Marin County, California, north of San Francisco, announced that they were "confident" that Alcala was responsible for the October 9, 1977, murder of 19-year-old Pamela Jean "Pam" Lambson, who disappeared after making a trip to Fisherman's Wharf to meet a man who had offered to photograph her.

With no fingerprints or usable DNA, charges were never filed, but police claimed that there was sufficient evidence to convince them that Alcala committed the crime.

In 2013, an image made public by Huntington Beach PD and NYPD of a dark-haired woman riding a motorcycle while wearing a yellow shirt was recognised by Thornton's sister.

Her body was found in Sweetwater County, Wyoming, along Interstate 80, in 1982, but was not identified until 2015 when DNA supplied by Thornton's relatives matched tissue samples from her remains.

[76] In 2017, the true crime series Murder Made Me Famous broadcast on Reelz did an episode about Alcala called The Dating Game Killer.

[78][79][80] In 2017, a biographical film about Alcala's life titled The Dating Game Killer was directed by Peter Medak and broadcast on the American television network Investigation Discovery.