User blog comment:Blood Reaper/Skyrim Patch Now Out!/@comment-4534710-20111129205849/@comment-108.41.196.20-20111129212407

Technically, all companions can die, when they run low on health, they collapse and beg for mercy from their foe. The enemy should stop assaulting the downed companion, but she/he can still die if the player misses in melee and hits him or her.