Linus F Phillip, 30, was shot and killed on March 23 at a Wawa gas station in Florida, after the police said he tried to drive away when an officer was about to search him, the Tampa Bay Times reported late on Monday.
Investigators arrived at Sylvan Abbey Funeral Home in Clearwater within 72 hours of the death, to take the the dead man's fingerprints. However, the attempt was unsuccessful.
Lt. Randall Chaney said it was done to access and preserve data on the phone to help them in the investigation of his death and a separate inquiry into drugs that involved him.
Chaney said detectives didn't think they would need a warrant because there is no expectation of privacy after death and this was affirmed by several other legal experts. However, Phillip's family said it was unethical.
"I just felt so disrespected and violated," Victoria Armstrong, Phillip's fiance, was quoted as saying.
"There's a ghoulish component to it that's troubling to most people," Mr Rose added.
While it is not clear what type of smartphone is at issue, Apple is the most widely-adopted phone that features fingerprint-unlocking technology.
Other companies including models from Google's Pixel and Samsung's Galaxy lines also offer similar bio-metric security.
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