he once stabbed an inmate nine times and spent the last 7 1/2 years in the idu. after a period of good behavior, he's requested a move to the chronic care unit. a steppingstone toward general population. >> you've done a lot of time in seg, and i don't know, maybe it's inevitable that you'll end up having to do more time in seg. >> i hope not. >> i keep trying to create situations for you so that it can be different. >> i've done a lot of violent things. in prison when you do violent things, it comes back to you. can't get away from it. >> dr. matias fears that if collins makes the move he might run into at least one of his old enemies. >> the situation on the side you'll probably end up on where the guy is pretty testy and not in real good control and i don't want him to confront you and then you feel like you have to defend it. and again, with the majority of -- >> is it somebody that i've already done somebody to or beat somebody up? >> well, i don't know. you have quite a list. let me think for a minute. i don't think so. i don't think so. all right. i will -

. >> before an inmate is sent to ad seg, he must first serve time in the i-detention unit or idu. in this highly secure cellblock offenders have even fewer privileges and almost no contact with each other. >> kind of like the prisoner jail inside the prison. they're not allowed to have hot pots up here or anything they can cook with. they have limited property they're allowed to have up here. anytime they come out of their cell they have to be restrained behind their back with an escort. the offenders that are up here are the most violent offenders in the prison so at any time, i mean, they might try to reach out and stab you through the bars. if you're on the catwalk, if they have a homemade weapon they can try to stab you that way. an offender who is good can slip the handcuffs if you're not careful and assault you that way. >> nicholas corbin was sentenced to one year in idu, the maximum amount of time. a fight went down in my cell house and i was accused of being involved with it. the individual needed to be taken to an outside hospital and because of that, i was sent up here.