Maybe they were cadaver dogs. Bloodhounds have amazing senses of smell but the other breeds have their own advantages that make them better suited.
EvidenceProf Blog: Dog Day Afternoon: Casey Anthony Trial Raises Questions About Cadaver Dogs
Deputy Pikett testified that all dogs have a more acute sense of smell than humans and that bloodhounds have an olfactory sense that is 26 times that of a human. Deputy Pikett explained that because a cadaver dog need not distinguish between the scents of different individuals and need only distinguish between the scent of human and animal remains, a breed such as a bloodhound that is traditionally known for its acuteness of scent is not necessary to use as a cadaver dog. Deputy Pikett further explained that a bloodhound is typically not a good cadaver search dog because bloodhounds are “not great obedience dogs” and typically must be worked on a lead, or leash. Deputy Pikett testified that in a large area search, a dog that can work off-lead is more credible because it is free to make an independent find, without the possibility that its handler will lead it to a particular area. Deputy Pikett said that other breeds, "such as Rottweilers mixed-breeds, Lab[radors] and so forth" can perform as cadaver dogs.
Edit to add: it's also been said that bloodhounds aren't exactly the most intelligent breed and can get confused sometimes with certain requests, like if a handler asks them to track something that is dead.