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A mysterious man who died of cyanide poisoning inside an Idaho church more than four decades ago has finally been identified, and investigators say his past raises questions about a possible connection to the still-unsolved 1982 Chicago Tylenol murders.
The man known for decades as the “Unknown Wanderer” was Dr. Mathew Francis Betkouski, an organic chemist with a history of discussing cyanide and poison, the Ada County Sheriff’s Office in Boise announced Wednesday.
Investigators said they couldn’t place Betkouski in Chicago during the final week of September 1982, when seven people died after taking Tylenol capsules laced with cyanide, and they are not naming him as a suspect.
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Dr. Park Dietz, a forensic psychiatrist who was consulted during the original Tylenol investigation and reviewed the evidence gathered on Betkouski, offered a stronger assessment.
“It’s an extraordinary thing to have been around at the beginning in 1982, and now today in 2026, to see very likely closure,” Dietz said.
Dietz said groups of forensic psychiatrists, psychologists and criminal profilers who were anonymously presented with information about Betkouski overwhelmingly considered him a viable suspect.
Betkouski died on Dec. 4, 1982, after walking into Sacred Heart Catholic Church in Boise. Authorities determined he died from cyanide poisoning, but he carried no identification, and his fingerprints produced no match.
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The mystery endured for decades until investigators traced one of nearly 30 keys found on him to Jacksonville, Florida, where Betkouski had lived. DNA recovered from his wallet and later compared with a sample from his brother helped establish his identity.
Investigators subsequently uncovered several details that drew their attention to the Tylenol case.
A former colleague recalled Betkouski discussing the “perfect crime” and cyanide, while another scientist recalled him saying poison could be introduced into over-the-counter capsules, according to investigators.
Authorities also found a map of Chicago and a bottle of sodium cyanide among belongings kept at his family’s Los Angeles home. Investigators stressed that the poison was not the potassium cyanide used in the Tylenol murders.
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Photos showed Betkouski had visited Chicago, but investigators determined they were likely taken in December 1981 and said they cannot establish that he returned when the Tylenol poisonings occurred.
Betkouski disappeared from his New Mexico home on Oct. 15, 1982, and turned up dead in Boise seven weeks later after apparently changing his appearance.
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Authorities have turned their findings over to investigators in the Chicago area and are seeking information about Betkouski’s movements and communications in 1982.
“This isn’t over,” Ada County Sheriff Matt Clifford said.
