A police corporal in Maryland was charged with second-degree murder on Tuesday in the fatal shooting of a suspect who had been handcuffed in the front passenger seat of his patrol car the previous night, the authorities said.

The corporal, Michael Owen Jr., a 10-year veteran of the Prince George’s Police Department, shot William H. Green seven times after a traffic stop on Monday night in Temple Hills, Md., on the outskirts of Washington, Henry P. Stawinski III, the county police chief, said Tuesday evening at a news conference.

Corporal Owen and another officer had been responding to a series of motor vehicle accidents in which Mr. Green, 43, had hit several cars and was suspected of being under the influence of an unknown substance, the chief said.

The officers had been waiting for another officer to arrive to evaluate Mr. Green for drugs when Corporal Owen opened fire, according to the chief, who said Mr. Green’s hands were cuffed behind his back at the time.