If they have substantial information that can lead to the arrest and conviction of another person, they will get a reduction. If they save the life of a prison worker, they will get a reduction. If they get a sentence commutation from the governor or president; and if they are in federal prison and can take the RDAP program, they will get a year off plus up to another year of guaranteed halfway house.
https://www.inmateaid.com/ask-the-inmate/how-can-someone-get-out-of-prison-sooner#answer
Accepted Answer Date Created: April 17,2015