Deadly Precision is a Combat Expression feature that facilitates such things as sneak attacks, ambush, and assassination.
Targeting the Living: This type of strike targets vital areas – joints, organs, etc. – of living creatures. It CANNOT be used against Undead versions of any living creature. If the attacker has no familiarity with an alien physiology or form, it cannot be used unless it can be extrapolated (ex: a humanoid form for an attacker used to dealing with humans).
SNEAK ATTACK / BACKSTAB