With its tinted windows, dark-blue paint and white interior, the 1990 Chevrolet Caprice attracted little attention as it glided through the region in that awful fall of 2002.

But the car -- in which police arrested John Allen Muhammad and Lee Boyd Malvo early one morning as they slept at a highway rest stop -- had been skillfully converted into what prosecutors allege was a roving killing machine.

Jurors are expected to see the Caprice -- one of the most damning pieces of evidence against Muhammad -- today when the judge leads them to a secured loading dock connected to the courthouse here where Muhammad is on trial for the six sniper shootings that occurred in Montgomery County.

They have heard about the car for three weeks, and its picture was the first image Montgomery County Deputy State's Attorney Katherine Winfree flashed on an overhead projector, referring to "that deadly Caprice" during her opening statements at the beginning of the trial.

The car, and a facsimile of the trunk brought into the courtroom by prosecutors, riveted jurors in Virginia, where Muhammad was convicted in 2003 of a single sniper murder and sentenced to death. The facsimile is not expected to be shown to the Montgomery County jurors.

"The car was one of the more compelling pieces of evidence," said Paul B. Ebert, the chief prosecutor of Prince William County, Va., where Muhammad was convicted.

Jurors in the Virginia case were fascinated by the modifications made to the car and scrutinized both the original and the reproduction of the trunk that was rolled into the courtroom, Ebert said.

When police stormed the Caprice early in the morning of Oct. 24, 2002, at an Interstate 70 rest stop in Frederick County, not only did they find Muhammad and Malvo asleep inside, but they discovered a trove of evidence, including a .223-caliber Bushmaster rifle tucked behind the back seat. The car, too, had modifications that prosecutors allege permitted the killers to roam suburban streets for three weeks and shoot 13 people without being detected.

The windows were tinted. A section of the firewall between the trunk and passenger compartment had been cut away, and the back seat of the sedan was hinged at the top so it could be lifted. This, prosecutors say, permitted a gunman to wiggle quickly in and out of the trunk while the vehicle was on the road.

A hole had been cut out of the metal above the license plate. The rectangular opening was beveled, or sloped, in such a way as to permit someone inside the car to see out without others seeing inside. It was big enough to accommodate the barrel of a gun, such as the Bushmaster.

Blue paint, matching the car's exterior, had been sprayed on the interior of the trunk lid. This, prosecutors theorized, permitted a shooter to lift the trunk lid slightly and peer out without being seen by passers-by.

The spacious trunk -- long a selling point for the Caprice, once Chevrolet's most popular luxury sedan -- was one of the features of the car that seemed to catch Muhammad's attention as he examined the vehicle on the sales lot of Sure Shot Auto in Trenton, N.J., salesman Chris Okupski testified yesterday.

Muhammad leaned into the trunk to inspect it before paying $250 and driving away with the car, Okupski said.

Chevrolet manufactured the Caprice from 1966 to 1996 and the model's popularity peaked in the late 1970s. It was the most popular make of police car for years, said Mark Clawson, a marketing manager with Chevrolet. In 1990, Chevrolet sold 38,000 Caprices to police, equipping them with heavy duty transmissions, suspensions, brakes and wheels, and thicker, heavier seats that prevent stabbing from behind, Clawson said.

Muhammad's Caprice had previously been owned by a township police department in New Jersey, Ebert said.

Muhammad knew how to work on cars and had once owned an auto repair business in Tacoma, Wash., according to testimony introduced in Virginia, Ebert said.

The modifications enabled the Caprice to elude authorities for 22 days, although numerous officers ran checks on the tags and several witnesses spotted the car at or near the scenes of the killings. The Caprice and Muhammad passed all checks.

Until a description of Muhammad's car was made public Oct. 23, 2002, authorities had said that they were looking for a white box truck. Hours after hearing about the Caprice with New Jersey tags, a refrigeration repairman spotted Muhammad's car and called police.

After taking Muhammad and Malvo into custody, officers searched the car and found a voice recorder with a threatening recorded message that had been previously played to authorities and a glove crammed in the hole above the license plate -- the mate to a glove found near the scene of bus driver Conrad Johnson's murder. They also discovered a stolen laptop computer with a saved map on which victims were marked by skulls and crossbones.

Although terrorists in other countries have modified cars into sniping vehicles, no other car in this country has achieved such notoriety, Ebert said.

"You can probably not find another car like this in history, at least in this country," Ebert said.

julie.scharper@baltsun.com