Sam's defense.
I was raised on a farm outside of Lusaka in Zambia by an Indian Sikh family. They had several dogs which all were working dogs & slept in a compound (unless they were let loose to catch the wildlife). My pet dog Sam slept with me. Sam was a pure bred bull-terrier - deaf as a post.
We lived in an old abandoned church and I slept in 1 of the rooms that was the refectory. Sam used to curl up on my the end of my bed.

1 night someone broke in. He came into my room. Sam woke up and bit him. Hard. on the leg. Sam's jaws locked (as they do when you're a bull-terrier). The guy woke all of us up screaming with Sam attached.

2 men had to push Sam's jaws closed and then squeeze the side of his mouth in order to open them again (no-one was brave enough to try the finger-up-the-bum technique & I can't blame them - Sammy was a mean dog). By that time the cops had arrived. They thought it was funny. We thought it was fairly hi-lar-ious. The thief clearly felt differently.

If he hadn't come into my room he would've got away with everything.
Silly man!
(Misery McUglywife an attention seeking sociopathic fuckstain., Sun 27 May 2012, 10:16, 6 replies)

Jaws locking is an urban myth. There is no physical part of any dogs jaw that causes it to lock.
(tyrellsOwl, Mon 28 May 2012, 7:55, closed)

Ridiculously strong jaw-muscles, though

(moon monkey is busy making memories worth repressing, Mon 28 May 2012, 9:41, closed)

This. Bull terriers really don't like to let go of things.

( monster munch person, man, woman... camera... TV?, Mon 28 May 2012, 9:49, closed)

I think there are millions of dog bite victims & hundreds of thousands of vets -
(the latter probably being a subset of the former) who would disagree with you.

Altho there is a wealth of info about this "myth" I challenge you to be able to pries certain dogs jaws apart once they have latched on without having to push their jaws inward and then release by squeezing the sides of their jaws (or shoving your finger up their bum if you are so inclined).
Hindsight - maybe they're all gay (or at least like anal) and they hope for that.
(Misery McUglywife an attention seeking sociopathic fuckstain., Mon 28 May 2012, 9:51, closed)

Strong jaws, that is all. There is no locking mechanism.

Edit: just had a quick google on my phone. Cannot find a single link to confirm its truth. Both reliable and unreliable sources agree it is a myth.
(tyrellsOwl, Mon 28 May 2012, 11:48, closed)

The challenge has been lain down.
...
(Misery McUglywife an attention seeking sociopathic fuckstain., Mon 28 May 2012, 12:03, closed)