Why are Bloodhounds used as police dogs?

The bloodhound has a sense of smell which is up to 1,000,000 times more sensitive than that of humans. Its nose has more than 200000,000 olfactory cells, which can lock onto an odour  and follow it for several days, despite the presence of other scents  along the way. Because of the bloodhound’s fine tuned olfactory system, it is commonly used as a police dog.