A 29-year-old man was convicted in federal court here today of participating with his brother and a Washington prostitute in the bludgeon slaying of another prostitute in a secluded wooded area just off the Baltimore-Washington Parkway.

The weeklong trial, which provided a rare glimpse into the seamy life of prostitution and massage parlor operations along Washington's 14th Street Strip, was interrupted yesterday when the defendant's brother slashed his left wrist with a razor blade in a holding cell behind the courtroom moments before he was to testify.

Deputy U.S. marshals struggled briefly with the man, Gilbert (Champ) Hill, 30, snatching the razor blade from him. One of the deputies then rushed into the courtroom to tell Judge James R. Miller that Hill apparently had tried to kill himself.

The jury was not present at the time, but Miller suspended court until the situation was under control again. Hill, subdued by marshals, was taken to a local hospital and later reported in good condition. He did not testify at the trial.

Today, the jury convicted his brother, Carlos Ricardo Hill, of kidnaping and second degree murder in the slaying of Pamela Mae Shipman, 24, a 14th Street prostitute whose battered and partly nude body was discovered just off the Baltimore-Washington Parkway near Powder Mill Road in February 1982. He will be sentenced later.

Both Carlos and Champ Hill, along with Sherri Webb, 22, an acknowledged prostitute and $200-a-day heroin addict, were indicted on murder and kidnaping charges in Shipman's death.

Webb, who said she earned up to $6,000 a week "turning tricks" in a massage parlor after leaving her suburban Baltimore home at the age of 16, pleaded guilty earlier this year to slaying Shipman with a 3 1/2-foot-long tire jack and was sentenced to 25 years in prison. Champ Hill was convicted last March of aiding and abetting the slaying and received a 35-year sentence.

Prosecutors Ty Cobb and David B. Irwin contended at the trial that the slaying stemmed from a feud between the two prostitutes. Webb testified that Shipman had set her apartment on fire in a dispute over a mutual male friend.

In retaliation, she said, she enlisted her current boyfriend, Champ Hill, and his brother, Carlos, to find Shipman on the night of Feb. 12, 1982.

She said they found her coming out of a house of prostitution just off 14th Street NW, forced her into Webb's red Lincoln and drove her into Maryland along the Baltimore-Washington Parkway and stopped.

Testifying in a husky, emotionless voice, Webb said the Hill brothers dragged Shipman into the woods and Webb took a tire jack from her car.

"Carlos said, 'We don't want any kidnaping charge,' and Champ told me to take the jack and get it over with," Webb testified. "Then I hit her over the head." she said.

"Several times?" asked prosecutor Cobb. "Yes sir," she said.

Defense attorney Leslie Gladstone attacked Webb's credibility, contending she lied about Carlos Hill's alleged role in the slaying to get a reduced prison sentence in the case.