From the 17-year-old D.C. sniper to a disgraced state politician, the new attorney for a 15-year-old Cockeysville youth who police say confessed to fatally shooting his family last weekend has had his share of high-visibility clients.

Joshua R. Treem, a Baltimore defense attorney and a former federal prosecutor, has been hired by Dulaney High School sophomore Nicholas Browning's court-appointed guardians to represent the teen. Browning is accused of four counts of first-degree murder in the deaths of his parents and two younger brothers.

"He fights like a dog for his clients," said Gerard P. Martin, who worked with Treem in the Maryland U.S. Attorney's office and paired with him for a time to represent former state Sen. Thomas L. Bromwell on charges of bribery.

"He'll raise every issue that can be raised," Martin said. "This kid's not going to be without a lot of help from Josh, and from what I knew about his father, he'd want him to have the best lawyer that he can have."

His father, John Browning, 45, was a real estate and corporate lawyer in Towson.

Treem was selected in 2002 from a pool of 100 lawyers who do federal criminal defense work to represent Lee Boyd Malvo, half of the sniper pair who terrorized the Washington region. In a New York Times profile, Treem was described as a "a successful private defense lawyer with a waterfront office, a reputation for being crafty and a whole bunch of awards after his name."

A graduate of the Johns Hopkins University and Duke Law School, Treem, 60, started his law career in the U.S. Attorney General's Honors Program and then worked in the Civil Rights Division of the Justice Department and as a federal prosecutor.

He is a founding partner of the Baltimore firm of Schulman, Treem, Kaminkow, Gilden & Ravenell, which has offices in the World Trade Center in the Inner Harbor, and has been named one of Maryland's top criminal lawyers by Baltimore magazine.

In 2001, he was recognized with the John Adams Award, given by Maryland's federal court system to honor attorneys for their work with indigent defendants in unpopular cases.

Despite his prominent clientele, those who know Treem say he is not one to steal the spotlight. He did not return a phone call yesterday for comment.

Treem represented Malvo in federal court, where a 20-count criminal complaint was dropped before going to trial. Malvo was then tried in a Virginia state court, where a judge ruled that the lawyers in the dropped federal case had no authority.

In a similar but less-celebrated case, Treem argued that a 22-year-old murder accomplice should be spared the death penalty because he was under the influence of the older co-defendant. The accomplice, Willis Mark Haynes of Bowie, received life in prison.

Treem's white-collar clients have included Bromwell, whom he represented for several years during a corruption probe until dropping out because of a conflict of interest about a week before jury selection was to begin. He also represented Annapolis lobbyist Bruce C. Bereano, who was convicted of mail fraud 1994.

"He's an incredibly talented defense attorney, and the child [Browning] is lucky to have him," said Maureen Essex, president of the Maryland Criminal Defense Attorneys' Association.

Treem replaces Steven D. Silverman as Browning's lawyer. Browning had personally contacted Silverman over the weekend, but after a Baltimore County Circuit Court judge appointed Browning's aunt and uncle from Virginia as his guardians, they contacted Treem.

Silverman, who defended heavyweight boxing champion Riddick Bowe against assault charges in Prince George's County, questioned in court Monday whether Browning's confession could be considered legitimate. Silverman confirmed yesterday that he was no longer associated with the case.

Police say Browning confessed to fatally shooting his father, then killing his mother, Tamara Browning, 44, and younger brothers Gregory, 14, and Benjamin, 11 at their Cockeysville home. Police say he used his father's handgun, then stashed it in a bush and spent the next day hanging out with friends.

He returned the next day, staging the discovery of the bodies and calling 911 himself, police say.

Bill Toohey, a spokesman for the Baltimore County Police Department, said police know of no motive for the shooting.

Though Toohey has said that Browning had a disagreement with his father, he said yesterday that it was not a specific complaint and that detectives do not know of any apparent "triggering incident."