There was only one witness that was sympathetic to Steve during his trial: Mr. Sawicki.  Sawicki states that he has known Steve for three years and that he is a good student and person.  Sawicki goes on to tell the jury that Steve is involved in his film club and that Steve plays an active role in his community.  Sawicki tells the judge, jury, and O'Brien (Steve's lawyer) that Steve is an honest. When questioned about how Steve is away from school, Sawicki tells the court that he knows him outside of school because Steve's films show him that Steve is a humane person with a deep character.  In the end, Sawicki states:

It is my belief that to make an honest film, one has to be an honest person.  I would say that. And I do believe in Steve's honesty.

Overall, calling Sawicki as a witness on Steve's behalf was a good idea of O'Brien's.  Sawicki made Steve look like a good person, not a monster, and Sawicki had not been in trouble with the law (unlike many of the other witnesses).