A federal judge has set an April 10 trial date for Carl Derek Cooper, who was charged in a triple slaying at a Starbucks coffeehouse, and prosecutors said they hope to decide by year's end whether to seek the death penalty in the case.

Cooper, 30, waived his right to a speedy trial at a hearing yesterday in U.S. District Court. Judge Joyce Hens Green said Cooper's decision will give attorneys on both sides ample time to prepare for a "complex case."

A federal grand jury returned a 48-count indictment against Cooper last month, charging him with racketeering, murder and other offenses in a series of crimes culminating in the July 1997 slayings of three employees at the Starbucks coffee shop at 1810 Wisconsin Ave. NW. By pursuing the federal indictment, prosecutors cleared the way to seek the death penalty against Cooper, who has been in custody since March. D.C. law does not provide for the death penalty, but federal law does.

Attorney General Janet Reno will have the final say on whether to seek capital punishment. She will act after getting input from U.S. Attorney Wilma A. Lewis and a special Justice Department review panel. Cooper's attorneys also have the opportunity to present materials for study.

Prosecutors said Cooper led a small but violent robbery ring for several years. He allegedly acted alone in the slayings of Starbucks manager Mary Caitrin Mahoney and employees Emory Evans and Aaron David Goodrich in what authorities described as a botched robbery attempt. Cooper also is accused of killing Sandy Griffin, a security officer, at a Northwest Washington apartment building in May 1993 and shooting off-duty Prince George's County police officer Bruce Howard at a Hyattsville park in August 1996.

Steven R. Kiersh, Cooper's court-appointed attorney, said he intends to challenge prosecutors' plans to use statements Cooper made to police as evidence against him. After his arrest, police questioned Cooper for 54 hours, eliciting written statements from him in which he said he was the Starbucks killer.

Kiersh said that Cooper was under duress and that his statements are unreliable. That issue likely will consume several days of pretrial hearings. Green has appointed defense lawyer Francis D. Carter to assist Kiersh in the case.