A Miami man shot dead by police as he chewed the face off a homeless person only had marijuana in his system, a coroner has found.
A police union official speculated at the time that Rudy Eugene, 31, had been under the influence of a category of street drugs known as "bath salts".
After stripping naked, Eugene attacked Ronald Poppo on a causeway in May.
Toxicology results found no alcohol, prescription drugs or adulterants often mixed with street drugs in his body.
An outside forensic toxicology lab also looked at the results and came up negative for bath salts, synthetic marijuana and LSD.
"Within the limits of current technology by both laboratories, marijuana is the only drug identified in the body of Mr Rudy Eugene," the Miami medical examiner's office said in a statement.
Eugene was shot and killed by a police officer after he ignored warnings to stop eating Mr Poppo's face.
Armando Aguilar, of Miami's Fraternal Order of Police, told a CNN affiliate at the time he believed the suspect could have taken a type of drug known as bath salts, citing four past overdoses in the Miami area where people had also removed their clothes and gone berserk.
Eugene's family told the Associated Press that he was not violent and did not drink or do drugs other than marijuana.
"There's no answer for it, not really," Eugene's younger brother, Marckenson Charles, said. "Anybody who knew him knows this wasn't the person we knew him to be. Whatever triggered him, there is no answer for this."
Dr Bruce Goldberger, director of toxicology at the University of Miami, said while the coroner's office is known for its thorough work, it would be a challenge to keep up with the pace of new formulations for synthetic drugs.
"There are many of these synthetic drugs that we currently don't have the methodology to test on, and that is not the fault of the toxicology lab," Dr Goldberger said.
"There is no one test or combination of tests that can detect every possible substance out there."
Rikkia Cross, Eugene's girlfriend, told the Miami Herald she is convinced the attack was the result of something "supernatural".
"Somebody did something to him, somebody put something on him. I know for sure that wasn't Rudy," she said.
Mr Poppo is recovering from the attack in a local hospital but will need additional surgery before he can consider reconstructing his face, doctors have said.