After a daylong preliminary hearing in Milford, Pa., District Judge Shannon Muir ordered Frein, 31, held for trial on murder and other charges that could bring the death penalty if he is convicted.
A packed courtroom watched surveillance video of the attack that showed the fatal shooting of Cpl. Bryon Dickson and the wounding of Trooper Alex Douglass outside their rural barracks in Blooming Grove, Pa., on Sept. 12.
Frein, restrained by shackles on his hands and feet and with a fresh haircut and new glasses, made no comment as the videos were played. He has been held since his capture on Oct. 30 at an abandoned hangar in the Pocono Mountains.
In addition to the murder charges, Frein is accused of terrorism, based on a call for revolution in a letter found on his laptop and for comments he is alleged to have made to authorities after his capture. Prosecutors have said they will seek the death penalty in the case.
The ambush at Blooming Grove drew national attention. Hundreds of law enforcement personnel joined the search for Frein as fear spread through the region. A team of federal marshals finally arrested him about 30 miles from the scene of the shooting.
The audience at Monday's hearing included some members of the family of the slain officer, according to reports from regional news outlets, including the Morning Call, Citizens' Voice and Philadelphia Inquirer. Spectators watched silently, the media reported, and one woman held the hand of a woman seated in front of her. Some in the audience reportedly cried.
Cpl. Warren Grabher testified that the surveillance video showed views from three cameras: one of the barracks entrance lobby and two of outdoor parking areas.
Dickson is seen opening the barracks door during a night shift change. Almost immediately, he collapses and falls to the ground. Douglass enters the scene from a parking lot and also falls after the shooter, who is hiding in the nearby woods, fires another round.
Douglass can be seen dragging himself into the barracks lobby. Others inside help pull him in.
Another trooper then crouches in the lobby, with gun drawn, apparently looking out the front door.
Dickson died and Douglass was seriously wounded in the ambush, which authorities have called an assassination.
Frein, of Canadensis, Pa., was identified as a suspect shortly after the shootings when a passerby found his vehicle partially submerged in a small pond near the state police station.
In addition to the video, Pike County prosecutors presented several witnesses. One trooper testified that bullets from the shooting were fired from a gun recovered at the site where marshals arrested Frein.
The defense did not offer any witnesses or evidence, a common procedure at this stage of the case.
John Schaaf, a deputy with the U.S. Marshals Service, testified about the capture, according to media reports.
Schaaf said he handcuffed Frein, who was on his knees, and searched him, finding a pocketknife but no other weapons. He said he also spotted a green nylon cord attached to "different metal devices."