Snakes, rats, dogs and pigs—some killers weaponize animals to pull off their heinous crimes.

In recent years, hair, blood, saliva, and other bodily fluids from dogs, cats and birds have helped solve several violent crimes in the U.S. and Canada. A&E True Crime profiles four instances where animal evidence helped convict a criminal.

Why do so many killers—Jeffrey Dahmer, Ted Bundy and David Berkowitz to name a few—abuse animals before targeting people? An expert provides insights on how the two behaviors are linked.

As much as people like to think of their four-legged friends as family members, legally, they're property.