Tim O’Brien, a broadcast journalist and lawyer who covered the Supreme Court for ABC-TV for 22 years and co-wrote a book on its notable capital cases, died Nov. 30 in Ponte Vedra Beach, Fla. He was 77.

He had been riding a bicycle and waiting on a sidewalk for a traffic light to change when he was struck by a truck that had veered off the road after an accident, Florida Highway Patrol officials told local media outlets.

Early in his career, Mr. O’Brien was weekend anchor and a general assignment reporter for Washington’s WTOP-TV from 1969 to 1972. He was then a television anchor in New Orleans until 1977, when he returned to Washington and began covering the high court for ABC.

After retiring from the network in 2000, he was a CNN journalist and participated in the coverage of the 9/11 terrorist attacks in New York and Washington. Later he was a regular contributor to a religion and ethics program on PBS.

Timothy Andrew O’Brien was born in New York City on July 11, 1943. His mother was an artist and his father a businessman. He graduated from Michigan State University in 1965 and received a law degree from Loyola University in New Orleans in 1976.

With longtime ABC News colleague Martin Clancy, Mr. O’Brien was author in 2013 of “Murder at the Supreme Court: Lethal Crimes and Landmark Cases,” a book that examined the court’s handling of death penalty cases, including the details of the crimes that led to the death penalty. As part of their research, they visited execution chambers and sat in electric chairs (with the electricity turned off).

“Unsparing journalistic prose grounds accompanying events in stark, gruesome facts underlying these precedent-setting cases,” a Publisher’s Weekly critic wrote in a review. “The result is an odd but effective mix of stomach-turning true crime stories and sophisticated analyses of Supreme Court decisions.”

Mr. O’Brien was said by colleagues to have been a fastidious dresser and smooth talker. On a research trip to an Oklahoma prison for their book, Clancy recalled, Mr. O’Brien was stopped twice by state highway patrollers for speeding, but he managed to talk his way out of a ticket both times.

During his years as a Supreme Court reporter, Mr. O’Brien was often detached to help cover other major news events, including the trial of President Ronald Reagan’s would-be assassin, John W. Hinckley Jr., and congressional hearings into the Iran-contra scandal.

A resident of Kensington, Md., Mr. O’Brien spent winters in recent years in Ponte Vedra Beach. Survivors include his wife of 49 years, Guadalupe “Petie” Moreno O’Brien; two children, Tracey McGee of Shrewsbury, N.J., and Timothy A. O’Brien of Washington; a twin brother; and five grandchildren.

In retirement, Mr. O’Brien was an enthusiastic bicyclist. He led week-long biking tours, with overnight stays covering routes that took him through New England.