The Reverend Jesse Jackson and about two dozen other demonstrators have been arrested outside an Oklahoma prison, protesting against the scheduled execution of Wanda Jean Allen, a black woman.
Tracy Rice, Jackson's attorney, said her client planned to stay in Oklahoma Co jail overnight.
She said Mr Jackson hoped to meet with corrections officials about witnessing Thursday's execution by injection of Allen.
Allen was convicted of the fatal shooting of her lover, Gloria Leathers, outside an Oklahoma City police station in 1988.
Allen, 41, didn't see the demonstration. An hour earlier she had been transferred to the Oklahoma State Penitentiary in McAlester, 120 miles away, for her execution.
A federal judge denied a 30-day stay of execution for Allen on Wednesday night.
Allen's lawyers said they planned to appeal against the decision at the US Supreme Court.
Since the 1976 Supreme Court lifting of a moratorium on executions, 685 people have been executed in the United States. Last year, 85 people were put to death.