Barry F. Kowalski, a Justice Department lawyer who prosecuted high-profile civil rights cases, most notably winning the convictions of two white Los Angeles police officers in 1993 for the beating of Rodney G. King — an episode that touched off one of the nation’s worst urban riots — died on Sunday at his home in Arlington, Va. He was 74.

His wife, Katie Zimmerman Kowalski, said the cause was complications of two strokes.

Mr. Kowalski was the assistant chief of the Justice Department’s criminal section in its civil rights division in 1991 when Mr. King’s car was stopped on a March night by four white police officers, who pulled him over for speeding.

A man in an apartment overlooking the scene captured images of the officers beating Mr. King with their batons, kicking him and shocking him with stun guns while he was on the ground. He sold the video to a Los Angeles television station for $500, and it was soon seen throughout the nation.

An all-white jury in state court found the officers not guilty of using excessive force. The trial was held in Simi Valley, a largely white suburb, out of concern that the officers might not get a fair hearing by a Los Angeles jury. The officers testified that their use of force was justified, and their lawyers maintained that the video did not prove otherwise. Mr. King, who had been on parole from a robbery conviction when he was arrested, did not testify.