He doesn't believe that Cole pushed Peter into the cave. Edwin was present during the incident, and he doesn't believe that Cole intentionally pushed Peter. He believes that it was an accident, and he doesn't want to see Cole punished for something he didn't do.
He feels guilty about his own role in the incident. Edwin was also involved in the bullying of Peter, and he feels guilty about what happened. He knows that he should have done something to stop it, and he feels that by backing up Cole, he can make up for his own mistake.
He wants to help Cole. Edwin knows that Cole is going through a difficult time, and he wants to help him however he can. He knows that Cole is innocent, and he wants to make sure that he gets a fair chance.