An 18-year-old Washington man charged with murder in the shooting death of a cabdriver last January had robbed the driver shortly before the shooting occurred, an assistant state's attorney told a Prince George's County Circuti Court jury yesterday.

The remarks of the prosecutor, Michael Whalen, came shortly after the murder trial of Eugene Banks began in Upper Marlboro. If convicted, Banks could face the death penalty.

However, Banks' attorney, Fred Warren Bennett, contended in court that the Killing was "an accident" that occurred when Banks saw a police officer near the cab and panicked.

Banks and Raymond White, 25, of 4336 V St., NW, are accused of killing two cab drivers within 12 hours in early January. The men are being tried separately in both murder cases.

In the case which opened yesterday, Banks is accused of killing part-time cab driver Robert McNeil, 37, in his cab as they rode along Route 1 in Hyattsville.

McNeil had picked the pair up at the intersection of Georgia and Florida avenues NW at 1 a.m. on Jan. 20, prosecutor Whalen said. As McNeil drove into Maryland on Rhode Island Avenue, Whalen said, Banks "produced a handgun" and forced him to pull to the side of the road.

"Raymond White jumped into the driver's seat, pushed McNeil over and took money," Whalen said. Shortly thereafter, after White had started driving the cab to Hyattsville, a county police officer noticed the cab was being driven erratically and pursued it.

When the pair noticed the flashing red lights of the police car, Whalen told the jury, Banks shot McNeil in the back of the head.

Bennett did not contest the basic facts as presented by Whalen, saying, "The issue is not only what occurred, but why it occurred."

When Banks "saw the police car coming [he] panicked and accidentally shot Mr. McNeil in the back of the head," Bennett said.

"At best, that's second-degree murder or manslaughter," he added.

The maximum sentence for second-degree murder is 30 years imprisonment. Ten years is the maximum for involuntary manslaughter.

A few hours before McNeil was slain, Prince George's County police discovered the body of cab driver Flora L. Washington, 41, behind a Landover warehouse. She had been shot to death.

A later investigation disclosed that Washington, like McNeil, had picked up her last fare at the intersection of Florida and Georgia avenues.

Both Banks and White have been charged with murder, kidnaping, and armed robbery in the two slayings.

However, White does not face the death penalty. Prince George's County Circuit Court Judge David Gray Ross, who is presiding at Banks trial, ruled that White should not face the death penalty since he did not kill either driver "with his own hand."