The actor, sentenced in October to 40 months behind bars for vehicular manslaughter, could be released as early as January 2009 thanks to good behavior credits, a source close to Garrison exclusively tells E! News.
When sentenced, Garrison was credited for 91 days he had already served and, combining that with California's early release program for good behavior, was looking at a possible 20-month stretch.
Garrison, who upon sentencing apologized profusely for the Dec. 2, 2006, car crash that resulted in the death of 17-year-old Beverly Hills High School student Vahagn Setian, is said to be in better spirits since being installed at the medium-security Golden State Correctional Facility near Bakersfield, Calif., after at least three transfers.
He has also begun to write again, having optioned six scripts before being cast on Prison Break in 2005.
"He is an incredible writer, and he is focusing on that now that he can," the source said.
"He said he reached the darkest depths he could imagine and could barely move his body, let alone write something," the insider continued, explaining how Garrison was too distraught to even pen letters, let alone scripts, from behind bars. "For the first time now, he has been able to actually see beyond and look into the future."
At his new facility, inmates are able to play basketball and check out books from the prison library, making it "by far the most comfortable" place Garrison has been since being locked up in August to undergo presentencing diagnostic treatment at the California Institute for Men in Chino.
However, the insider says the former Prison Break star remains very distraught over what he did, adding, "It is depressing, but he is holding on."
A police investigation revealed that Garrison's blood-alcohol level was 0.20 percent and he had cocaine in his system when, while driving in Beverly Hills, his SUV jumped a curb and hit a tree, killing Setjian and injuring two 15-year-old passengers. He had met the high-schoolers at a nearby supermarket and had accepted their invitation to accompany them to a party.
They had just left the gathering, where Garrison's attorney said he had one drink, when the accident occurred. The actor suffered minor injuries.
"I just want to say how sorry I am to the Setian family," Garrison said in court in October before he was sentenced. "I am sickened by my behavior on that night. My thoughts keep coming back to that night.
"I want to show that my walk with sobriety will be very easy. I want to help other kids not make the same mistake I did."