Federal prosecutors charged yesterday that four defendants arrested last Saturday in a large-scale drug distribution case allegedly sought in the last few days to hire someone to kill the government's key witness against them.

D.C. police Lt. Ronald Harvey testified in a federal magistrate's court that a confidential source, whom he identified only as "S-1," told him Thursday that the four men allegedly hd pooled their financial resources to raise $25,000 and taken out a contract for delivery of the witness' "head."

Law enforcement sources said yesterday that the witness, identified as John Henry Tate, is currently in protective custody of the government. A source siad it was not known whether anyone had actually been hired as the would-be killer.

In a sworn statement submitted to the court, Harvey said that S-1 told him that the four men allegedly intended to "take certain steps" so that they could find Tate before he had a chance to testify against them.

In the same sworn statement, Harvey said he was told on Wednesday by the detective under his command that one of the defendants, Joseph Lester Brown, had stated the day before that he would "trade his life for the life of the witness, John Henry Tate." t

U.S. Magistrate Lawrence S. Margolis ordered that the four men, arrested last Saturday and then released after posting high money bonds, be held in jail without bond pending a further hearing on the case Monday.

The four defendants, Ronald Hinton, 36, Clarence Watts Jr., 38, and his brother, Thomas Watts, 37, and Brown, 41, are all charged with distribution of Preludin, known on the streets as "Bam" and used as a stimulant and a heroin booster. Hinton and Thomas Watts are also charged with possession with intent to distribute Preludin. No charged have been filed in the alleged murder plot.

Law enforcement officials allege that the four men have been major suppliers of amphetamines on the streets for the past eight years. They were arrested after undercover police staged a discount sale in which they displayed 22,000 Preludin tablets -- borrowed from the manufacturer -- and offered them at cut rates. A fifth man arrested Saturday, Marvin Lee Cobb, 30, was not implicated in the alleged murder-for-hire scheme.

Preludin, actually a diet pill, is considered one of the most commonly abused drugs in Washington. Most of the drug is brought to the District from out-of-town suppliers.

Assistant U.S. Attorney George J. Terwilliger III asked Margolis to revoke the bonds for all four men based on the information that Harvey had received this week from his informant, who claimed in his statement to the police that he had a face-to-face conversation with one of the defendants about the alleged murder contract. Neither Harvey's source nor the defendant he spoke to was identified.

Defense lawyers for the drug suspects vigorously protested that they were unable to challenge the credibility of the source's information without knowing his identity, but Margolis repeatedly refused to order the government or Harvey to provide the informant's name.

Margolis said the defense lawyers could presnet witnesses in their clients' behalf at the Monday hearing.

Harvey, who supervised the 10-month investigation that led to the arrests last weekend, testified that the informant known as S-1 telephoned him at his office Thursday and told him about the alleged murder-for-hire scheme. Harvey testified that S-1 is a paid informant he has known for 6 to 10 months, but that he was not paid for the information about the alleged plot.

Later the same day, Harvey said S-1 told him during a second telephone call that a person described only as "very close" to one of the defendants told S-1 that the alleged amount of the contract was $25,000 and that in return the defendants allegedly wanted Tate's head.

When prosecutor Terwilliger asked Harvey if that allegation meant the defendants "literally" wanted Tate's head, the detective said that they did.

Harvey said during the conversation, S-1 referred to the nicknames "Jo-Jo," "Heavy," "Ruggie" and "Mother." Harvey said it was made clear to him that S-1 was referring to the Watts brothers, Hinton and Brown.

Under cross-examination by defense lawyer William J. Garber, Harvey testified that he had not asked Tate whether he had received any threats since the four defendants were arrested. Harvey said he did not know where Tate was being held in protective custody.

Margolis issued bench warrants for all four men Thursday after he became aware of the information Harvey said he received from S-1. Hinton, Brown and Clarence Watts has been free on #25,000 bond, while Thomas Watts had been released on $35,000 bond.