I had a rescue dog that reportedly killed chickens when she was a puppy. She was the sweetest smartest dog i ever had, but very timid. For years if we raised our arms above our waist she would cower, if we raised our voice, she would cower. It was a challenge to discipline her because of her obvious past trauma so we trained her to go into timeout, if she misbehaved we would get out an egg timer and she would have to sit under the dining room table until it went off. This really worked as a deterrent.

When she was older she had some health issues and we did some x-rays for unrelated reasons. We discovered that when she was young (before we got her) someone had broken both her front legs. The vet said the nature of the breaks suggested they were deliberate. It was the first time in my life I felt actual rage.