yes i could, especially if they were a person who deliberately hurt a child or molested one. if you are in a situation where self defense is involved then you dont know if your capable untill its upon you. i do however think that people are to soft on some people.
while i dont condone the stupid crap the military did at the prisons, i dont have a problem with them going hard ball on someone they KNOW is somehow involved. hit them with psycological crap first and see if you can make them crack.
can i kill someone..... yes. do i want to.... hell no, and i pray that i never will have to.