How does jokosta reason with opedius that he can't be guilty of his father death especially since the prophecy was that Laois would be killed by their son?

Jocasta convinces Oedipus that he cannot be guilty of his father's death because the prophecy stated that Laius would be killed by his own son. As far as Oedipus knows, his father Polybus was killed in a different way, and the son he believed to be Laius's killer is not actually his biological son. Jocasta uses this confusion to reassure Oedipus of his innocence.