What important function does Jocasta play in the play and the film other than being Oedipus mother/wife?

Aside from
the fact thatis ' mother, wife, and the mother of his children, she plays a role in the drama
unlike the rest of the .  In the midst of his trials, Jocasta is the one voice that seems to
support Oedipus through reason.  She speaks very matter of factly in Act II when she explains to
Oedipus why she does not believe in prophesy.  Unlike the rest of the people in Thebes (and
therefore also the original audience of the play), Jocasta dares verbalize her disbelief in
something everyone else takes very seriously and without question.

Ironically, while Jocasta's confidence makes her sound very rational and even somewhat
convincing, her actual proof for why she does not believe in prophesy (the
story of the crossroads where Laius was murdered) turns out to be the exact evidence that
confirms Oedipus' mistake and shows him his own blindness.  She unknowingly convinces him that
Tieresias was correct all along.

When she hangs herself at the end of the
play, I think it symbolizes the fact that Jocasta really thought herself innocent all along.  I
believe it shows that her intentions were pure and only confirms her ignorance.  When she finds
out the entire truth, and realizes how her mistakes contributed to the , her guilt is so great
that she does not feel worthy to live.  There is something noble in this decision, despite how
much the audience may pity her.