I can't imagine that. It's totally untrue IRL. Provably, demonstrably, as a matter of fact not opinion untrue. People are terrible at differentiating dead and unconscious, even in the very best circumstances, without doing stuff like finding a pulse or listening for a heartbeat. Sometimes even then, as various horrible-but-true incidents indicate. I regularly play with two people with MDs, several others with significant first aid training. They'd look at me like I was completely insane if I said it was possible to perceive this.
So there's no fictional justification for normal mortals with human-like characteristics doing this.
Now, there are easy fantasy solutions - one obvious one is that people can see spirits leaving bodies. This is true in a small subset of fantasy. If it's normal to be able to perceive that, like there's a flash of light, or an actual spirit floats out, or something, then suddenly you have 100% fictional justification, but it's not right to suggest humans can conventionally perceive this, and that's demonstrable medical/scientific fact.
So I'd suggest you go with something where spirits can be seen leaving the body, or maybe the spirits in all sentient creatures can sense the echo of other spirits or something (raises a lot of questions though, whereas seeing them leave is obvious).