A Maryland man admitted yesterday that, while driving with a suspended license last year, he smashed into an unmarked patrol car on Route 50 in Anne Arundel County, killing a decorated officer with the Maryland Transportation Authority.

Albert G. Antonelli, 33, of Queenstown, Md., pleaded guilty to vehicular manslaughter. Under the terms of a plea agreement, he is expected to be sentenced to five years in prison, which will be suspended after three years, and five years of probation.

Antonelli, driving more than 70 miles an hour, slammed into the patrol car July 20, 2004, as Cpl. Duke G. Aaron III completed paperwork after a traffic stop. Aaron, 29, of Pasadena, who had won his department's Officer of the Year award three times, suffered severe head injuries and was pronounced dead later that day.

"Nothing will ever be enough," the officer's widow, Jennifer Aaron, said of yesterday's plea. "He is alive, and my husband is dead. He can go home and tell his family he loves them. I have to say it to a grave, and don't get to hear it back."

According to a factual summary presented by the prosecution, witnesses said that Antonelli was driving erratically before the crash and that his speech was slurred and slow afterward. He tested positive for several prescription drugs, including the tranquilizer commonly known as Valium, but prosecutors said those drugs had been prescribed to him.

A small bag containing cocaine residue was found under a seat in Antonelli's truck, and six syringes were found elsewhere in the vehicle. Blood tests suggested that he had used cocaine, according to the summary, but experts did not agree on when or on what influence, if any, the drug may have had on Antonelli at the time of the crash.

Duke G. Aaron III was a decorated state officer.