A surveillance photo of victim Paula Prince purchasing cyanide-tampered Tylenol at a Walgreens drugstore in Chicago. Credit: Chicago Police Department
For nearly four decades, he was known only as the Unknown Wanderer. Now, the Ada County Sheriff’s Office (ACSO) announced the identity of the man who died inside a Boise Catholic church in December 1982 — and revealed that the same case has identified a possible connection in one of the most infamous unsolved crimes in American history: the 1982 Tylenol poisonings.
ACSO investigators have identified the man as Dr. Mathew Betkouski.
Background
On Dec. 4, 1982, an unidentified man died by suicide inside Sacred Heart Catholic Church in Boise. He carried no identification—only a large sum of cash and a typed note signed “Wm. L. Toomey.” The Ada County Coroner determined the cause of death to be cyanide poisoning. Despite national media coverage, including sketches distributed to newspapers across the country and a 1990 “Church Doe” segment on the second season of Unsolved Mysteries that generated thousands of tips, the man remained unidentified for nearly 40 years.
In 2019, Ada County Sheriff’s Office Cold Case Detective Tim Cooper reopened the investigation, cross-referencing the case against more than 17,000 missing persons records. The break came from a single engraved key found among the man’s belongings, which led investigators to a residential street in Jacksonville, Florida. There, detectives identified a property owner who had disappeared in 1982 and was later declared deceased in absentia. Photo comparison and familial DNA confirmed his identity: Dr. Mathew Betkouski.
Identifying the Unknown Wanderer opened an unexpected door. Investigators found that Betkouski had worked in two drugstores during his undergraduate studies, giving him working knowledge of pharmacy operations. Those who knew him described a history of volatility, including a documented fascination with explosives. Cooper’s investigation grew to include numerous interviews with people who had known Betkouski throughout his life, along with a review of thousands of pages of documents and more than a dozen personal letters. Among the details that emerged: colleagues recalled Betkouski discussing the idea of a “perfect crime” and describing cyanide as a means to kill without detection.
Based on this body of evidence, ACSO has identified a possible connection between Betkouski and the 1982 Tylenol poisonings — an unsolved case that claimed seven lives in the Chicago area and remains one of the most significant unsolved crimes in U.S. history. ACSO has shared its findings with the Chicago Police Department.
“Knowing I’d consulted with the FBI on the Tylenol murders in 1982 and had studied product tampering, Detective Tim Cooper called me in July of 2021 and began sharing data from his investigation. By December 2021, Tim’s findings convinced me he’d identified a viable suspect for the 1982 Chicago Tylenol murders,” said Dr. Park Dietz, MD, PhD, forensic psychiatrist. “Without identifying the unknown wanderer or the location of his death, I presented Tim’s findings to large audiences of forensic psychiatrists and forensic psychologists, and Tim and I jointly presented them to a large gathering of law enforcement criminal behavior analysts. Polls of each audience showed overwhelming agreement that the wanderer was a viable suspect for the 1982 Chicago Tylenol murders, and many were as convinced as I that Tim had solved the crime.”
Additional details of the possible connection between the Unknown Wanderer and the Tylenol poisonings will be presented in an upcoming, brand-new Unsolved Mysteries documentary: Unmasking the Tylenol Killer. The Ada County Sheriff’s Office worked closely with the Unsolved Mysteries team throughout the course of this investigation, and the full account—including evidence not detailed yet—will be revealed when the documentary premieres on Oct. 9, 2026 on The Roku Channel.
“Our goal in partnering with Unsolved Mysteries was simple—we wanted more tips, and we wanted more evidence to come forward,” said Ada County Sheriff Matt Clifford. “Detective Cooper has done incredible work on this case, but there are still a lot of questions we don’t have answers to, and we’re hopeful this documentary helps us get there.”
What’s Next
The Ada County Sheriff’s Office has shared its findings with the Chicago Police Department. The Ada County Sheriff’s Office is not releasing the full body of supporting evidence at this time.
“Mathew Betkouski lived in five states over the course of his life — California, Texas, New Mexico, Ohio and Florida,” said Cooper. “We’re hoping that getting his story out generates new leads, not just for this case, but for others we may not even know about yet. I’m especially interested in learning more about his movements between October 15 and December 4, 1982.”
Republished courtesy of Ada County Sheriff's Office