IMHPO...it's really the degree of strength that certain breeds of dogs can inflict with a bite that I think contributes to the idea of locking jaws.
Pit Bull - Wikipedia, the free encyclopedia
Any dog's jaws can be locked in a closed position by surgically-correctable jaw abnormalities,[22] but there is no evidence for the existence of a physiological "locking mechanism" in the teeth or jaw structure of normal pit bull-type dogs[23] so this is not a factor in the number of fatalities attributed to them;
however, pit bull-type dogs often exhibit "bite, hold, and shake" behavior and refuse to release when biting,[24] so some pit bull rescue organizations and advocacy groups
recommend owners of pit bull-type dogs carry a "break stick" to lever their dog's jaws open if it bites a person or animal.[8][25]
Fatalities reported in the United States (2006-2008)
For more details on this topic, see List of people killed by dogs in the United States.
The following table summarizes the number of pit bull-related fatalities in the United States from 2006-2008 as reported by news organizations.[20]
Dog Bite-related Fatalities in the United States
Year------Total------Involving Pitbull-type dogs
2006------30--------16 (53%)
2007------35--------20 (57%)
2008------23--------16 (65%)
2009------16--------8 (50%)
This is how I would like to see a Pitbull out in public...again, it's my personal opinion and one based on personal experience, too.