Prosecutors' paid use-of-force expert says a Cleveland police officer acted unreasonably when he climbed onto a police cruiser and then the hood of a car to fire shots at two suspects after a high-speed chase in November 2012.

The expert testified Monday at the voluntary manslaughter trial in Cleveland of patrolman Michael Brelo, who prosecutors say fired the final 15 rounds of a 137-shot barrage and killed two unarmed suspects.

The expert says officers had reason to think their lives were in danger after the sound of the suspects' car backfiring was mistaken for a gunshot, prompting the chase. But he says the car had stopped and no longer posed a threat when Brelo fired his final rounds.

Brelo's attorneys will question the expert Monday afternoon.