Frein avoided capture for 48 days before USA marshals caught him at an abandoned airplane hangar more than 20 miles from the Blooming Grove barracks in northeastern Pennsylvania, where authorities say he killed Cpl. It spoke of revolution and said "the time seems right for a spark to ignite a fire in the hearts of men".
Frein faces charges including murder of a law enforcement officer and terrorism.
The defense will take over when the prosecution wraps later this week. He killed Cpl. Bryon Dickson, a 38-year-old Marine veteran who left behind a wife and two young sons, and critically wounded Trooper Alex Douglass, who was shot through both hips as he came to the aid of his mortally wounded comrade and suffers from a range of health problems. A Chester County jury of 12 jurors and five alternates is hearing the case, which began April 4.
As the verdict was read, Frein, standing with his hands clasped, puffy circles under his eyes, stared blankly at the jury.
The trial moves into a penalty phase today, with the same jury deciding whether Frein deserves the death penalty or life in prison without parole.
After the prosecution finished its case Tuesday morning, the defense called no witnesses and presented no evidence.
The letter was found on a computer thumb drive at the abandoned airplane hangar where Eric Frein was captured 48 days after the sniper attack in Blooming Grove.More news: Republicans Take First Congressional Election of Trump Era
Pike County District Attorney Ray Tonkin called Frein a terrorist and told reporters after the guilty verdict that he intends to seek "full justice" for the victims and their families.
In 10 days, prosecutors presented 54 witnesses and introduced almost 540 pieces of evidence, including pages detailing the shooting from a journal Frein wrote while on the run, DNA analysis linking Frein to the Norinco rifle used during the shooting, pipe bombs found at a campsite Frein used, a letter to his parents about the need for a revolution and his videotaped confession from the night of his capture.
Wednesday was the 11th day of trial. However, court filings show they hired two expert witnesses: Carol Armstrong, a neuropsychologist, and Louise Luck, who specializes in developing mitigating evidence for death penalty cases.
The focus now shifts to the impact of Frein's crimes.
Defense attorney Michael Weinstein in 7-minute long closing remarks: acknowledged mountain of evidence points to Frein. Inside, investigators found shell casings matching those found at the barracks and Frein's driver's license. He had been on the run for 48 days, sparking a costly, intense manhunt.
Frein ended: "And as time goes by, if circumstances change, if my spark has good tinder, then I may be able to return one day".