Forensics
Elementary, my dear Watson.

Maybe when a lot of blood is produced, making ' a bloody mess ' in a room, the killer leaves bloody footprints for a handful of rooms that you could spot with the skill?

Likewise maybe a blood trail when a body is moved?

Last one: maybe a skilled forensics person could tell what type of blood spatters are on someone's clothes when they look? Like what type of weapon may have caused the backsplash?

I would love for forensics to allow a lot of 'comparisons'.

Compare a weapon to a wound. With a good enough roll, know if that kind of weapon is responsible. With an even better roll, know if that specific weapon is responsible.

Compare a treat to a room. With a good enough roll, tell if that tread has been present recently. With an even better roll, tell if that specific shoe/boot was in the room recently.

Compare a person/blood sample.body part with a corpse. See if they are the same person.

Compare a person/blood sample/body part with a blood splatter. Tell if that was the person's blood.

Compare a weapon/item/armor/clothing with a corpse/person/blood sample or body part. See f that person has worn/touched that item recently.

Of course, once can add modifiers to make it harder or easier. How long has it been? Were gloves worn? Was an sealed suit worn? Inside or outside? City or badlands?

In general I think the ability to do a variety of matching would make this skill amazing.. Assuming all of this isn't already possible of course.