A New Zealand-born hacker found dead in his San Francisco home in July died from an accidental overdose of heroin, cocaine and other drugs, according to a coroner's report.
Barnaby Jack, 36, a director of security consulting firm IOActive Inc, achieved cult status after demonstrating ways to hack ATM machines.
A toxicology screen found evidence of "acute mixed drug ... intoxication" from heroin, cocaine, the antihistamine diphenhydramine and Xanax, which combined to cause Mr Jack's death, AFP reported, citing a report by the San Francisco Medical Examiner.
An autopsy found no visible or palpable evidence of trauma on the body.
In 2010, Mr Jack famously demonstrated at the annual Black Hat security conference in Las Vegas how he could make ATM machines spit out cash.
He was scheduled to demonstrate techniques for remotely attacking implanted heart devices when he died.
He is survived by his mother and sister in New Zealand and girlfriend in California.