It's a bug in and of itself that his corpse is even still there after all that time. Suggests the quest holding his alias isn't shut down properly. He was there when I walked into the Jarl's longhouse, dead in his bed where I slit his throat back in December. I can't imagine the smell after all that time! Nobody thought to check on the poor guy?

At the very least, his NPC probably needs the unique body cleanup, but that doesn't work if he gets that assigned after he's already dead.
A bug has been filed for this on the UHFP tracker, but if it's only a matter of getting back on the Jarl's good side with radiant questing or something then that's not a problem. Just rather inconvenient that somehow they know it was me who killed the housecarl.