How does Jocasta try to assure Oedipus that he not guilty of Laius' death?

Jocasta reveals that an oracle once came to Laius and told him that he would be killed by his son, though she too reiterates that Laius “was killed by foreign highway robbers / at a place where three roads meet” (715-6). She tells Oedipus that, three days after his birth, Laius pierced the ankles of the child and had him cast forth “upon a pathless hillside” (720).