Sad to say, Gless role was typical of the time. Women in movies mostly to be decorations for men and/or for sex/make out scenes. I'm so happy she got the chance to go on to more interesting roles like Debbie Novotny in Queer as Folk.
I think the purpose of the wife was simply to show that he has a wife and children. This allows shots for the upset judge to ponder the legal system's unfairness while his wife watches on helplessly, and shots of him looking at his children playing, reminding us that he has kids and hey how would he feel if they were murdered by a monster?
As the previous poster says, this was unfortunately typical of the time. Definitely a film that does not pass the Bechdel Test.