A letter indicating a chief government witness may have lied under oath has prompted an attorney for a death-row inmate, convicted of killing a Montgomery County police officer and a store security guard, to ask for a new trial.

Courtland K. Townsend Jr., attorney for James A. Calhoun, said a recently discovered letter written by an admitted lookout in the March 1981 robbery and shooting at the W. Bell & Co. store in White Oak names another accomplice as the true gunman.

In a letter to Curtis Wayne Monroe, Calhoun's convicted accomplice in the double slaying, the witness, Herbert Smallwood Jr., admitted he lied while testifying during the trial, the attorney said.

Monroe also filed a motion for a new trial in Montgomery County Circuit Court, citing the letter as evidence, according to his attorney, Barry Helfand.

Smallwood's letter identifies codefendant Burl Courtney as the gunman, directly contradicting his own testimony, Townsend said. In court, Smallwood identified Courtney as the second lookout and said he saw Calhoun and Monroe running from the store directly after the shooting.

Monroe was found guilty of murder in June in the shooting deaths of Officer Phillip Metz and security guard David Myers and is awaiting sentencing.

The state's attorneys office declined comment.