convicted murderer doing life down to a low level drug user?
The type of security prison which holds a mix of people as described in the question is; Maximum security prisons.
Security prisons for Convicted Murderers
Supermax prisons otherwise termed Maximum security prisons are the highest-level security prisons, whose objective is to hold inmates that pose extreme security threats.
Inmates in such prisons have little to no time outside of their cells, very few activities and very little contact with other humans as they pose a threat to the society.
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