In Monster by Walter Dean Myers, why was Mr. Sawicki an important witness for Steve Harmon's defense?

Throughout the trial, Kathy O'Brien, Steve Harmon's lawyer, continually mentions how important it is for Steve to distance himself from the other individuals involved in the crime. James King, Richard "Bobo" Evans, and Osvaldo Cruz are all thugs who have a bad reputation. Steve Harmon is simply a good kid who began associating with these individuals in order to fit-in and be cool. Mr. Sawicki runs the film club at Steve's school and is Steve's teacher. O'Brien uses Mr. Sawicki to testify that Steve Harmon is a good person who has a positive reputation. When O'Brien asks Mr. Sawicki what he thinks about Steve, Mr. Sawicki comments that Steve is an outstanding young man who is bright, talented, and compassionate. Mr. Sawicki also testifies that he believes that Steve is an honest person. Mr. Sawicki's testimony is significant because his positive opinion of Steve portrays Steve to be an honorable, trustworthy young man. The jury takes into account that Steve is not like the other individuals involved in the case, who do not have any reputable people to speak highly of them. Mr. Sawicki's testimony essentially distances Steve from James, Bobo, and Osvaldo.