Florida cannibal did not have bath salts in his system "The problem today is that there is an almost an infinite number of chemical substances out there that can trigger unusual behaviour," said Dr Bruce Goldberger, Professor and Director of Toxicology at the University of Florida, US. Dr Goldberger said that the medical examiner's office in Miami is known for doing thorough work and that he's confident they and the independent lab covered as much ground as possible. But it's nearly impossible for toxicology testing to keep pace with new formulations of 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. The challenge today for the toxicology lab is to stay on top of these new chemicals and develop methodologies for them, but it's very difficult and very expensive. Dr Goldberger said. There is no one test or combination of tests that can detect every possible substance out there. An addiction expert said she wouldn't rule out marijuana causing the agitation. "It could have been the strain of marijuana that increases the dopamine in the brain, such as sativa," said Dr Patricia Junquera, assistant professor at the Department of Psychiatry at the University of Miami Miller School of Medicine. There are two strains of marijuana called sativa and indica. The sativa increases dopamine and gives you energy while decreasing pain threshold. Indica is a "sleepy high," she explained. "People don't really know what the amount of either is in each little packet of marijuana," she explained. And we can't differentiate between the two in the blood, much less in a dead person. She also suggested that if Eugene had a mental disorder, "the marijuana could have increased even further the dopamine levels and aggravated the situation. So that can't be ruled out. It's not clear what led to the May 26 attack on Ronald Poppo, a 65-year-old homeless man who remains in hospital. Eugene's friends and family have said he was religious, not violent and that he didn't drink or do drugs harder than marijuana. "There's no answer for it, not really," Eugene's younger brother, Marckenson Charles, said in an interview. Anybody who knew him knows this wasn't the person we knew him to be. Whatever triggered him, there is no answer for this. Surveillance video from a nearby building shows Eugene stripping Mr Poppo and pummeling him, before appearing to hunch over and lie on top of him. The police officer who shot Eugene to death said he growled at the officer when he told him to stop. Charles, Eugene's brother, said the family does not plan to pursue any legal action against the police for shooting Eugene. They used the force they felt was necessary, even if we don't agree with that,' he said. He said that Eugene has been buried. Shortly before the attack, a person driving on the MacArthur Causeway told an emergency services dispatcher that a "completely naked man" was on top of one of the light poles on the causeway and "acting like Tarzan." Still, police have said little about what may prompted Eugene to attack Mr Poppo. Mr Poppo has undergone several surgeries and remains in hospital. His left eye was removed, but doctors said earlier this month they were trying to find a way to restore vision in his right eye. He will need more surgeries before he can explore the options for reconstructing his face, doctors have said. A message left with the hospital was not immediately returned. Mr Poppo's family has said it had no contact with him for more than 30 years and thought he was dead. Eugene's girlfriend, meanwhile, has said he never showed any signs of violence. Yovonka Bryant said she and Eugene often read the Bible and the Koran together, and often watched a religious television program in the mornings. She said she never saw Eugene drink and only saw him smoke marijuana once at a party.