Just found this SA very interesting
For sniffing out crime and missing persons, science backs blood-detection dogs
But the smell of blood can also be used to locate it at crime scenes. In recent years, several law enforcement agencies in Europe and Australia have introduced blood-detection dogs, which are trained specifically for blood evidence.
By using this distinct dog unit, a large search area can be screened as a potential crime scene in cases of assault, missing persons, mass disasters or suspected homicides where a body may not be present.
Blood-detection dogs are a recently specialised unit under a broader grouping of scent-detection dogs used by law enforcement. The dogs’ highly sensitive sense of smell can locate a range of target odours including drugs, explosives, human bodies (known as “cadavers”) and now blood.