You can't guarantee anything to anyone in prison. The following is from a CBC News story on what Russell Williams could expect when he was sentenced to prison. Of course, it's referring to Paul Bernardo. I also read somewhere that Bernardo is/was even harassed by the guards.
"Bernardo has been attacked and harassed at the prison. He was punched in the face by another inmate while returning from a shower in 1996. In June 1999, five convicts tried to storm the segregation range where he lives and a riot squad had to use gas to disperse them."