JACKSONVILLE, Fla. (AP) — When the Animal Planet channel's Victoria Stillwell needs an expert on fatal dog bites and aggression, she calls one man: Jim Crosby, a retired sheriff's deputy from Jacksonville.

Crosby is a canine crime scene investigator. He travels around the country, helping animal control departments, lawyers and police agencies study dog aggression cases. He's widely considered to be one of the nation's only forensic experts on dog bites.

Crosby's goal is to find out why a dog attacked a person, and whether the dog can be rehabilitated — or if it needs to be put down.

He says that in many cases, dog bites are more complex than they appear in the media. This year, he will publish a book called "Working the Worst: A Guide to Investigating Dog Related Fatalities."