A former D.C. police officer pleaded guilty yesterday to distributing drugs while on duty and in uniform, admitting that he regularly shook down dealers and sold drugs while he was under the influence of them himself.

Shawn P. Verbeke originally faced up to 20 years in prison on a charge of conspiracy to distribute ecstasy and methamphetamine. But after prosecutors added a firearms count yesterday, Verbeke could be sent to prison for life when he is sentenced Oct 29.

Verbeke, 30, pleaded guilty to both charges in U.S. District Court in Alexandria. Wearing a gray and white prison uniform and speaking in a firm voice, he said he routinely shook down dealers at nightclubs in the District and engaged in about 30 illegal drug transactions in Northern Virginia. Court documents said he worked with a group of co-conspirators.

Law enforcement sources said that the investigation is continuing and that others could face charges. Court documents indicated that Verbeke is cooperating with the probe. A Virginia-based task force of the federal Drug Enforcement Administration began investigating Verbeke after he was named by a trafficker who had pleaded guilty in Alexandria.

Verbeke, a former U.S. Capitol Police officer, joined the D.C. police in 1999 and left in June 2002. He was a patrol officer in the 3rd Police District. Police officials have declined to comment on the case.

Authorities arrested Verbeke, a former Marine, June 8 in Ohio, where he was living with his mother. The arrest came days before he was scheduled to move to Kuwait to work for a contracting firm aiding the U.S. military.

Verbeke did not make a statement at yesterday's hearing, and his attorney, David W. O'Brien, declined to comment afterward.

Asked by U.S. District Judge Leonie M. Brinkema what he hoped to gain from the drug dealers he approached at nightclubs in the District, Verbeke said: "Drugs and currency, your honor.'' He then acknowledged that he often was under the influence of methamphetamine during the shakedowns.

Court papers filed with Verbeke's plea said he routinely distributed methamphetamine and ecstasy "while on duty and in uniform" and "regularly carried a firearm during these narcotics transactions.''

In one instance, according to court papers and law enforcement sources, Verbeke pulled over a car at 22nd and P streets NW for what was supposed to be a traffic stop. He approached the car in uniform, clipboard in hand. But a bag of drugs was on the clipboard, and Verbeke acknowledged yesterday that he sold the driver about 3.5 grams of methamphetamine for $400.

Court papers said Verbeke had supplied the driver with drugs "regularly."

Verbeke also admitted that he distributed ecstasy and methamphetamine at an apartment in Ashburn and at "other locations within the Eastern District of Virginia.''

Shawn P. Verbeke joined the D.C. police in 1999 and left in 2002.