More than 200 drug cases in Prince George's County could be dismissed from court, state prosecutors say, because of cocaine use allegations against a key prosecution witness -- the county police officer assigned to handle narcotics that are seized as evidence from defendants.

The officer, now suspended without pay, is a 14-year veteran whose job was to transport drug evidence from the county police property warehouse to the Maryland State Police crime laboratory. If requested by a defendant's attorney, his testimony would be required to establish exactly what evidence was found with the defendant and that the evidence had not been tampered with.

Without the testimony of all persons who have had custody of a confiscated drug and drug-related evidence, the drug and its chemical analysis cannot be admitted as evidence.

In a 1983 decision, the Maryland Court of Special Appeals granted a new trial for a man who had been convicted of conspiracy to distribute heroin because prosecutors failed to produce all persons who had had custody of the drug and other drug evidence.

The officer currently in question has been unavailable to testify in court since the beginning of July because he is being treated for a psychiatric problem, police sources said. County police suspended the officer without pay almost two weeks ago after his urine tested positive for cocaine. The officer has not been charged with a criminal offense but is to have a hearing before a police trial board next month on administrative charges relating to the cocaine.

Circuit Court judges have been postponing trials in which the officer was a state witness, most recently on Friday when Judge Jacob Levin postponed for the second time the trials of two men charged with possession with intent to distribute PCP because the officer "was unable to testify."

Assistant State's Attorney Sheila Tillerson had subpoenaed the officer in Thursday's case, but he failed to appear. On Friday, the officer showed up in court with his attorney, Alan J. Goldstein, who told Levin that he would advise the officer not to answer questions from the defense attorney concerning allegations of drug use or tampering with drug evidence.

Bruce Marcus, attorney for the two men, said he "objected vehemently" to the postponement. Marcus said one of the defendants has been waiting trial in the county detention center since December. "That is a lengthy and oppressive pretrial detention," Marcus said, "especially where the integrity of evidence is questionable."

Levin released the two men from custody on personal recognizance.

The status of the cases will not be resolved until a trial judge determines how broad the officer's Fifth Amendment rights are, prosecutors and defense attorneys said, and that decision will likely be appealed.

State's Attorney Arthur A. Marshall Jr. acknowledged in a letter last week to Police Chief Michael J. Flaherty that the allegation against the officer "well could lead to a dismissal of a number of drug cases."

Deputy State's Attorney Michael Whalen said in an interview that the officer could be an essential witness in "well over 200" drug cases in circuit and district court. Whalen said police first notified his office that the officer was ill "two or three weeks ago" but was not told about the drug allegations until July 15.

Alex Williams, Marshall's opponent in the Sept. 9 Democratic primary for state's attorney, said that the confusion about the 200 drug cases "is a clear indication of what I've been saying all along about Marshall's lack of attention to the prosecution of drug cases."

"He's the chief law enforcement officer in the county," Williams said. "He should know about the problems in the police department. But he is not concentrating on what he should be doing."