"What normal, other dogs can do, like jump on somebody or behave like a dog, a pit bull can do that and be deemed dangerous," dog trainer Beverly Kingsbury said.
Kingsbury has trained dogs in Pacifica for 15 years. She says any dog, not just a pit bull, can react to tiny changes in its owner's body chemistry. That's why some dogs can detect a seizure before it happens and why a dog might behave differently if its owner becomes pregnant.
"They are aware of changes in our chemistry. What they do with those changes though could be on an individual basis. They can do nothing, or they can alert us, or they can get upset or frightened," Kingsbury said.
For a smaller dog, that frightened behavior might be just a nuisance. For a pit bull, it could be deadly.
But when it comes to laws restricting the ownership of pit bulls, or requiring them to be neutered, Kingsbury worries a lot of it has to do with the breed's bad reputation.
"The pit does have a strong jaw, but it's not the strongest and it's not the only one," she said.
At the San Francisco animal shelter, administrators say they have seen a 25 percent drop in the number of pit bulls that wind up in these kennels since the city started requiring that breed to be spayed or neutered. They say they have also seen a 40 percent drop in the number of pit bulls they've had to euthanize.
"Neutering males reduces their testosterone level and potentially their aggression," Animal Care and Control Director Rebecca Katz said.
Katz says most serious dog attacks in San Francisco have involved un-neutered males. Females and males who are fixed do not pose as much of a problem. But there is a problem is getting people to comply.
"We get, regularly get calls and complaints about intacft pit bulls that people have seen in different parts of the city," Katz said.