Do we look different when dead, there is always a need for identification?

Depending how we die, yes we can look different, all our muscles completely relax and faces can change shape, then there is timeline, as blood and fluids drain out of top of body or into them if angled down.
There is also the legal requirement to 100% get the body identified, as people have been wrongly identified before, either accidentally or by fraudulent means to make people believe they are dead.

Very different if time has passed. But in TV shows I guess the whole identification thing has to follow the rules for legal IDing someone, not just assuming who the body/victim is.