All prisoners are supposed to have the collar on. That's the point. So yes, if the guards see you, your only choices are to go to prison or to fight them. That's normal.
All inmates who leaving the prison, on the other hand, are flagged as kill-on-sight even if you used the teleport statues to literally only leave the prison for 3 seconds and came back in. That's intentional, but a pretty stupid design decision and should be changed.
Also because the guards are really REALLY hard to kill! I tried to defeat them with cheats (only offline don't worry) for this reason i doubt whether it is a normal thing ...
