The official autopsy also confirmed that tissue from Brown was found on the exterior of the driver’s side of Wilson’s vehicle.

“Someone got an injury that tore off skin and left it on the car,” Graham said. “That fits with everything else that came out. There’s blood in the car, now skin on the car, that shows something happened right there.”

The toxicology test, performed by a St. Louis University laboratory, revealed tetrahydrocannabinol, THC for short, in Brown’s blood and urine.

Alfred Staubus, a consultant in forensic toxicology at the Ohio State University College of Pharmacy, said that THC could impair judgment or slow reaction times but that there was no reliable measurement to make those conclusions.

States that have legalized marijuana have struggled with the issue of how to measure impairment.

“The detection of THC in the postmortem blood of Michael Brown really indicates his recent use of marijuana (within a few hours) and that he may or may not have been impaired at the time of his death,” Staubus wrote in an email.

Editor's note: