Detective BloodTrak Tracking Device!

[Dr Zoidcrab]

I think a better implementation would be to scan a blood sample, and then the pinpointer would point to anyone within visible distance who has that blood on their clothes or hands.

Actually, yeah. Something that just highlights a sample you give it would be a better tool

Maybe even include fingerprints or glove fibers. Then it's more about tracking them based on following the path of items they've interacted with.

Though I guess that doesn't do anything for helping find dead bodies

Bodies are generally found covered in their own blood, so it could still be useful for that.