Shapeshifter (2005)

A dishonorably discharged female soldier is hired as a prison guard at an old prison.  This turns out to be the place where they assign the guards that aren't very good.  The guards stand amidst the prisoners discussing the convicts mental disorders. So much for discretion, but the prisoners don't seem to mind as they're all sitting on huge leather couches, waiting to be transferred to the new portion of hte jail.

When a new prisoner with no ID is admitted, he has an unidentifiable accent and a strange tattoo on his chest. After watching the prisoner on closed circuit television as he chews into his forearm and pulls out a pendent, the new guard suggests that maybe they should check on him since he's now performing a ritual of some sort.

Well they should have done that sooner because as they're carrying the trance like prisoner out of the cell, he transforms into a monster with a meaty head and a body that looks like a ratty old gorilla suit. Honestly, it looks like something right out of the 1950s film, Robot Monster.

After kicking the female guard and chowing down on the other one, we cut back to the female guard with the prisoners and she's wearing a wife beater. Wait... where did her prison guard uniform go? Did the monster kick it right off her?  There's no explanation offered.

With a monster on the loose, their brilliant plan of escape is to lock themselves in one cell and then rip open the ceiling to crawl into which leads to a convenient human sized opening into an old office. Seriously?  From here on it is all monster vs. everyone else.  Overall it's pretty stupid.