A Perth police officer cleared after shooting a dog dead on a suburban street in November has been stood down after testing positive to methamphetamine on Monday.

On Wednesday, a WA Police investigation into the dog shooting found the officer was justified in discharging his weapon at the animal based on reports the dog was acting aggressively before its death.

WA Police Commissioner Karl O'Callaghan told Radio 6PR the police officer was not tested for drugs on the day of the Kinross shooting but did pass a random drug test a day later.

He defended WA Police's decision not to name the police officer as one of the people who tested positive for drugs but conceded it was an "extraordinary coincidence".