You can peruse the
NIJ Stab Resistance Standard if you want, but a corrections officer I know puts no faith in this stuff, just in huge numbers of huge guys throwing everything they have at one inmate with any sharp, pointy object, because anything can and will happen. Hopefully you already have a skeptical view of the effectiveness of handgun-round resistant vests. You already know that you don't want to get hit nearer than three inches from the edge of any panel, that even wearing a vest, most of your frontal area is still unprotected, and so on. OK, take that uncertainty to the umpteenth power with stab-resistant armor.