Nine years later, Douglas T. Cummins still can recall the cold metal of the loaded revolver pressed against his head by one of two masked gunmen during an early morning robbery at the W. Bell Co. in White Oak.

Cummins, the sole survivor of what a prosecutor described as a "cold-blooded, deadly ambush" that ended in the slaying of a Montgomery County police officer and an alarm system technician, had failed twice to open a jewelry safe for the robbers.

"I didn't know the combination to the safe," Cummins told a Montgomery County jury yesterday in the opening day of a trial to decide for the second time whether convicted murderer James A. Calhoun should be sentenced to death. Cummins, already shot in the chest, said Calhoun "hit me on the side of the head with the pistol. He then cocked the gun, put it to my head, and told me if I didn't open it on the third try, I was dead. The third time it opened."

During two hours of testimony yesterday, Cummins told his story in a calm, straightforward manner. But the trial, expected to last two weeks before Circuit Court Judge L. Leonard Ruben, has big stakes for Calhoun and indirectly, many of the 12 other prisoners on death row in Maryland.

"This is not an exercise in data processing," Roger Galvin, one of three attorneys for Calhoun, said in his opening statement. "This is not an exercise in filling out a form. This is a process in deciding whether a man will live or die."

Calhoun's resentencing trial is only the third for a Maryland death row inmate since a June 1988 U.S. Supreme Court decision. In that case, Mills v. Maryland, the court said a form previously used by jurors in capital punishment cases was unconstitutional because it failed to give enough weight to mitigating circumstances. Under the corrected procedure with a revised form, jurors are instructed to consider any mitigating circumstances that they believe exist, regardless of what is presented at trial.

The Calhoun death penalty trial is being closely monitored by state officials. "For each year of delay, the perception is that the death penalty is futile," said Roger Rosenblatt, the assistant attorney general who handles Maryland death penalty appeals. Rosenblatt, who listened to yesterday's opening statements in Rockville, said the Mills decision "pushed us back to square one for executions."

The appeals process can take up to seven years for death row inmates to exhaust appeals in state and federal courts. Congress is considering legislation to streamline the federal appeals process. There has been no execution in Maryland since 1961.

No distinct pattern has surfaced yet in death penalty resentencings in Maryland, Rosenblatt said. In the two previous cases, one inmate received a life sentence, and the other was sentenced to death, he said.

Yesterday, Assistant State's Attorney Robert Dean asked the jury to reinstitute Calhoun's death sentence. "This procedure is not a bloodthirsty search for vengeance," Dean said. "A finding for the death penalty will show that justice is finally done."

Calhoun was found guilty by a Montgomery County jury of the murder of Montgomery County police Officer Philip C. Metz during the March 27, 1981, robbery at the store on New Hampshire Avenue. The slaying occurred 10 weeks after Calhoun had escaped from the Lorton prison, where he was serving a 20-year sentence for armed robbery, Dean said.

In opening statements yesterday, defense attorneys portrayed Calhoun, now 37, as a reformed man who was a "calming influence" at the Maryland Penitentiary in Baltimore. "He keeps people from doing things that would make the place unmanageable," Galvin said. "He is a bit of the glue that holds that place together."

Also yesterday, codefendant Herbert Smallwood, the lookout and getaway driver, testified that the robbers escaped with about $6,000. Smallwood, who is incarcerated in the D.C. jail on drug and bail-jumping charges, was given a reduced sentence in 1981 in exchange for his testimony against Calhoun and a second gunman, Curtis W. Monroe, who was sentenced to life in prison.