On a show I watch, a prisoner (minimum security, if it makes a difference) is suspected of a murder and interrogated by a guard. I know that you give up many of your constitutional rights in prison, but AFAIK prisoners still get something akin to due process when they’re accused of crimes once they’re already in prison.
So anyway, could the inmate have refused to speak without an attorney? What could the guards have done to her (legally, that is, not extra-judicially) if not? Could they remove privileges, up to an including segregation, if she didn’t talk?
The right to remain silent applies to criminal procedure used by the police and judicial branch, not administrative procedure used by the prison. When prison officials decide to put someone in segregation because of something they did in prison, they’re not doing it because it’s a crime but because it breaks prison rules. An act may do both.
Any statements a prisoner makes to prison officials cannot be used as evidence in court unless we Mirandize them first - which virtually never happens. If a prisoner commits a serious crime that’s going to be taken to court, we call in the state police and they conduct the investigation for that purpose. We conduct our own investigation for internal purposes like MichaelEmouse described. If you’re a prisoner, for example, and you assault another prisoner, the police will charge you with assault, the DA will prosecute you, and the judge will sentence you to five more years in prison. Meanwhile, we’ll charge you with violation of the prison rules against assault and take away your TV privileges for five years.
It makes our system sound trivial but many prisoners are more upset by the prison charges than they are by the criminal charges. If you’re already doing a long term sentence in prison, adding five more years to the end of it is largely a gesture, especially when most of these sentences are given concurrently as part of a plea bargain. But losing his TV watching privileges is something that affects his daily living.