After a few months, parents of a toddler noticed their friendly lab-sheperd mix behaving aggressively when the sitter arrived, and acting defensively toward the child.
After 5 months (?? trust your dogs, people!), they put an ipod recorder in the sofa, expecting to hear the
dog being abused. Instead, it was their son, cursed at and slapped. The woman was sentenced to 3 years in the slammer.
Hero Dog Saves Boy from Abusive Babysitter - ABC News