The time an inmate will spend in the "hole" or the SHU (special housing unit) is entirely up to the disciplinary hearing officer. Depending upon the offense, it could be as little as a couple of days or as long as several months. They can definitely write letters from the SHU.
https://www.inmateaid.com/ask-the-inmate/how-long-do-an-inmate-stay-in-a-hole-when-they-act-up-and-when-theyre-in-the-cell-hole-can-they-write-letters-to-the-outside#answer
Accepted Answer Date Created: May 07,2014