Is Hypnosis Testimony Valid? How The Hillside Strangler Case Was Involved In This Debate

There’s a longstanding difference of opinion when it comes to the reliability of testimony of individuals while under hypnosis.

Proponents maintain it’s a “valuable tool which often produces evidence unobtainable by other methods,” according to a 1981 MacNeil/Lehrer Report — although the same report noted, “Opponents say hypnosis is unreliable and it may produce tainted evidence.” 

 “The Hillside Strangler: Devil in Disguise”, a new Peacock docuseries streaming now, takes a deep dive onto how Kenneth Bianchi was convicted for committing a series of murders in Los Angeles in the late 1970s — and how a glaring spotlight was shone on hypnosis because of the case.

 Ken Bianchi was implicated in the murders of 10 girls and young women in L.A. between October 1977 and February 1978 following his arrest for a double murder in Bellingham, Washington in 1979. He had an unusual excuse when he was caught.

 “Bianchi, supposedly under hypnosis, had told psychiatrists in Bellingham, Wash., that he had an evil alter-ego named Steve Walker,” UPI reported in 1982.

In those taped conversations he also named his adoptive cousin Angelo Buono as his accomplice in the slayings.

 Bianchi, who, along with Buono, posed as law enforcement when they abducted victims, was hypnotized nine times from March to June in 1979, according to another UPI report.

 Dr. John Watkins, from the University of Montana, and Dr. Ralph Allison each interviewed Bianchi while he was purportedly under hypnosis.  Each expert supported the theory that Bianchi had multiple personality disorder, according to “The Hillside Strangler.”

Experts recruited by prosecutors, however, concluded that Bianchi was faking his hypnotic state, as well as the alternate personalities of Steve and Billy, who also emerged during the sessions. 

Dr. Martin Orne, an expert on hypnosis and multiple personality disorder, gave Bianchi tests to verify the veracity of his claims, as seen in the Peacock series, tests that Bianchi failed.

One telltale sign that he was apparently pretending to be under hypnosis was the way Bianchi responded to prompts. He would rise and pretend that he was greeting and shaking hands with another person. The behavior gave him away as a fake, Orne thought, according to the docuseries.

After a series of interviews with Bianchi, Orne “helped convince a judge” that his claim of multiple personalities given while supposedly under hypnosis “was a fabrication,” the New York Times reported in 2000. 

Bianchi eventually admitted in court that he made up his alter-egos, UPI reported. He ultimately pleaded guilty to murders in both Washington and California, which allowed him to avoid the possibility of the death penalty if convicted.

To learn more about the case and the role of hypnosis in it, watch “The Hillside Strangler: Devil in Disguise” streaming now on Peacock.