ST. PAUL, Minn. (AP) -- A toxicology expert says he believes a black motorist who was shot to death during a traffic stop in Minnesota was under the influence of marijuana.

Glenn Hardin, a former supervisor of Minnesota's state toxicology lab,
testified Thursday as a witness for Officer Jeronimo Yanez. Yanez is charged
with manslaughter in the death of 32-year-old Philando Castile last July in a
St. Paul suburb.

Defense attorneys have argued Castile was stoned at the time of the shooting,
which happened in the seconds after he informed Yanez that he was carrying a
gun. Hardin said he examined autopsy reports showing Castile's blood levels of
THC, the substance in marijuana that gives a high.

Prosecutor Jeff Paulsen attacked Hardin's testimony by citing studies he said
show there's no way to determine marijuana intoxication from blood samples.