Toxicology experts and law-enforcement officials have questioned the results of toxicology tests which appear to show that Rudy Eugene, the so-called "Causeway Cannibal," had no other drugs besides marijuana in his system the day he attacked elderly homeless man Ronald Poppo on Miami's MacArthur Causeway.

"We are not testing for everything that may be out there," leading toxicologist Dr. Barry Logan told the Sun Sentinel. According to Logan, toxicology labs are only capable of testing for some 17 out of a 100 possible chemical compounds currently used to produce synthetic cannabis, AKA K2 or Spice.

The designer drug known as "bath salts" is similarly difficult to detect. Out of hundreds of possible chemicals, toxicologists only test for 40.

"This is always a moving target," said Logan. "As soon as a test exists for something, there are new compounds waiting in the wings. We are always a step behind." Asked his opinion on Eugene, Logan said his delusional state was "consistent with bath salts."

University of Florida toxicology professor Dr. Bruce Goldberger concurs with Logan. "To say marijuana could have induced this behavior is simply outrageous," he told the Sentinel. "No matter how sick mentally or physically a person is, they don't go around eating people's faces, or barking at police, or eating a dog, like what happened recently in Texas."

Synthetic drugs are popular among their users for two reasons: They can generally be obtained over-the-counter, and most are undetectable by standard drug tests.

"These are the guinea pig drugs of 2012," said Jim Hall of Nova Southeastern University's Center for the Study and Prevention of Substance Abuse. "The people using these drugs are risking their lives, their minds and their kidneys. Some of these people have had to be put on dialysis for the rest of their lives."

[photo via AP]