Carter- Witness

John Book's time in the Amish community changed him in many ways, the movie showed his growth as a person, beliefs and his actions. John initial change after joining the Amish community is his self centered outlook on life to actually caring for others, the death of his close friend and partner really was the straw that broke the camel back in a sense. Earlier in the movie Book was also injured and the Amish family took care of him, attending to his wounds when he awoke he realized there was more to life than only looking out for oneself.
The next change in Book's character deal with his response to authority, he shows some understanding of authority after he has joined the Amish community and realizes following rules is more important than personal pleasure. The first problem with authority is shown early on in the movie when Book arrest a black man out of a bar and basically commits police brutality. This scene showed that he would do anything to accomplish his personal goals even if it involved getting his hands dirty. This changes in the movie slightly, when he is presented with the opportunity to have a sexual encounter with rachel, he shows restraint because of the rules the Amish have even though she was willing. This is much different from early on in the movie when he had no respect for the rules, allowing the son to play with the empty gun and making out with Rachel in earlier scenes.
The third change Book showed in "Witness" is abrupt change in violence, in philly that was all he knew growing up and this showed throughout the movie as he continued his violent acts even after living with the Amish. The reason why the town was found is because he made a commotion that led to his whereabout being reported to the police, the change came close to the end when he tells Schaeffer that is was "ENOUGH!". Book at this point was fed up with the violent lifestyle that has only caused him pain. He then rips the gun out of Schaeffer hand and arrested him. This showed a very important character trait that was finally reversed for a positive effect.

The one thing that doesn't change throughout the movie in my opinion is Book's ambition or drive, even though he was safe living basically a second life with the Amish community he never forgot the goal. This was always a job to Book in the end, I believe this is also the reason he didn't stay and become a family with Rachel. Many believed him joining the Amish community was the clear cut choice especially after the relationships he developed but he was always focused on solving the case and bringing the right people to justice.