ST. LOUIS (AP) — A man who was with Anthony Lamar Smith on the day he was killed by a St. Louis police officer says he believes Smith was unarmed.

Jason Stockley’s first-degree murder trial began Tuesday. The white former officer is accused of fatally shooting Smith, who was black, in December 2011.

Stockley and his partner witnessed what they thought was a drug transaction outside a fast-food restaurant. Smith sped away, prompting a chase. After the chase, Stockley shot Smith five times.

Prosecutors say Stockley planted a gun in Smith’s car after shooting him. Stockley’s attorney, Neil Bruntrager, said in an opening statement that Smith had a gun in the car and Stockley shot him in self-defense.

But Smith’s longtime friend, Kirkwin Taylor, testified that he rode with Smith to the restaurant. He said he didn’t see a gun and didn’t believe Smith had one in the car.