The D.C. Court of Appeals yesterday overturned the burglary conviction of a 29-year-old District of Columbia man and ordered a new trial for him because the prosecutor told the jury that convicted him that the man was a liar.

The court also ruled that the prosecutor, an assistant U.S. attorney, acted improperly when he suggested that the defendant's presence at the trial "facilitated his ability to fabricate his testimony" in that he took the stand after testimony adverse to his case had been given. The prosecutor also improperly commented on the defense's failure to call witnesses to corroborate his account, the court said.

Writing for the court, Associate Judge Julia Cooper Mack said the court is "concerned by the frequency with which" prosecutors violate "standards of permissible argument."

The unanimous opinion cited 18 cases dating from 1968 and indicated that these were a representatives sampling involving improper conduct by prosecutors.

The case yesterday arose from last year's trial of Phillip P. Dyson, who was charged with second-degree burglary and destruction of private property at a northeast drug wholesale warehouse.

During closing arguments, the prosecutor, Michael Lehr, who no longer is with the U.S. Attorney's office, told the jury that the defendant and his only witness, a juvenile, both had lied.

"It is for the jury to decide whether a witness is truthful and an attorney may not inject personal evaluations and opinions as to the witness's veracity," the appeals court said.

Since the evidence against Dyson "was not particularly strong," the jury's decision would have been based primarily on whether they believed the defendant or the police, the court sid. Therefore, the prosecutor's improper comments might have prejudiced the jury against the defendant,

The court also criticized the prosecutor for questioning Dyson's constitutional right to be present at his trial and for improperly questioning the lack of corroborating witnesses.