With a special hitscript maybe. The guards currently use the default hitscript (somwhere in the pkg/combat section I think). There's bound to be a way to write a hitscript so that each time a guard connects with her halberd that it immediately kills the target and destroys its body. This, of course, should probably not be applied if the target is a player character, but if you're feeling especially evil, you might apply it to them too.
I'm sure someone with a little more coding experience can give you some more specific advice, but I'm pretty sure that's a good place to start looking.