A key witness to a Georgetown bank robbery last November, who had complained to D.C. police when the holdup suspects were freed on personal bond, refused yesterday to testify as a prosecution witness in the case and was held in contempt of court.

Vincent Dorsey, a tow-truck driver for the city's Department of Transportation, gave no reason for his silence in U.S. District Court here yesterday. But in a letter to robbery detectives after the holdup last November, Dorsey's complaint was clear.

"He didn't think it was right for those people to be back on the street," Sgt. Edward Dory, head of the bank robbery squad, said, summarizing the letter yesterday.

In an interview, the detective said Dorsey also appeared concerned about his own safety because two of the suspects live near the Northeast Washington neighborhood where Dorsey picks up his tow truck on workdays.

On the morning of the robbery last Nov. 14, Dorsey chased three men wearing ski masks as they fled from the National Savings and Trust building at 2929 M St. NW, watched them get into a car and then radioed the vehicle's license number to his Transportation Department dispatcher. Dorsey continued his pursuit but lost sight of the getaway car. Police arrested three suspects sometimes later.

Dorsey gave a complete statement to police about what he had seen. Yesterday, however, Assistant U.S. Attorney William Collins told Judge Gerhard Gesell that Dorsey had torn up his subpoena and would not come to court to testify.

Gesell then ordered Dorsey taken into custody. He was picked up and brought to court by four deputy U.S. marshals and held briefly in the courthouse cellblock. Dorsey still refused to testify, giving no explanation. cAfter letting him consult with a lawyer, Gesell then held him in contempt of court.

Dorsey was next taken before U.S. Magistrate Jean Dwyer on the contempt charge and released from court custody pending a further hearing before Gesell on Feb. 20.

It was Dwyer who last November released the three bank robbery suspects on personal bond, with the standard requirements such as maintaining regular contact with the court's pretrial services agency.

The suspects -- Lewis Blakeney of 1815 Q St. SE and twin brothers Stanley and Bradley Holmes of 4404 Quarles St. NE -- were all legally eligible for personal release since they had local addresses and no prior history of failure to appear for court appointments.

Describing the "angry tone" of Dorsey's letter to the police robbery squad, Sgt. Dory said yesterday that Dorsey "felt he had done a good deed for the city and then you turn around and they [the suspects] are back out on the street." Dorsey could not be reached for comment yesterday.

Because Dorsey refused to testify, the eyewitness statement he had given police about the holdup scene, cannot be admitted into evidence at the bank robbery trail, which could be a significant blow to the government's case.

Prosecutor Collins had told the jury in his opening statement that Dorsey would be a witness, but yesterday Collins wound up resting the prosecution without Dorsey's testimony. The defense also completed its presentation of evidence.

The jury is expected to hear closing arguments in the case today and begin deliberations.