Steve is a typical teenager in a lot of ways. Most notably he is struggling for some kind of self identification. On one hand, he wants to be tough like the guys in his neighborhood.
"I had looked at him and wanted to be tough like him."
On the other hand, Steve may want to be tough looking and acting like those guys, but he also knows that he doesn't have a violent bone in his body. His cell mates might beat the tar out of each other, but Steve never once contemplates using violence against others.
It's hard for Steve to come to terms with how the prosecution is trying to make him look like a monster, because Steve views himself as a fairly good kid overall. He admits that he's not perfect, but he has a strong moral sense about him.
"I know that in my heart I am not a bad person."
The people that he is close to know that about Steve too. Even one of Steve's teachers describes him as "talented, bright, and compassionate." Those aren't exactly words that describe a violent, thuggish gang member.
One of Steve's main interests is filmmaking. He's good at it, and enjoys it. What's more important though is that filmmaking becomes his way of coping.