Dear Ms. Cathey,
Thank you for posting your request on History Hub!
The location of his prison records, if they were retained, depends on when he was incarcerated and which institution incarcerated him. If he was in a state prison, you should begin by contacting the Department of Corrections for that state. Depending on the age and retention schedule of the records, they may refer you to their state archives.
If he was in a federal civilian or military prison, please reply with further details about which prison he was in and the time period when he was incarcerated. If you prefer, you may submit your inquiry privately via NARA’s Contact Us form. Please note that not all federal inmate case files were scheduled for permanent retention.
Recent records of federal inmates still may be in the custody of the Federal Bureau of Prisons.
We hope this information is helpful. Best of luck with your research!