The prosecution is not permitted to re-file a petition to violate probation on the same ground asserted in the first violation of probation hearing, which was not sustained for lack of proof. Defendant was on probation when she was charged with possession of stolen property, a camera. A joint violation of probation/preliminary hearing was held, at which a Proposition 115-trained police officer was the sole witness. The court held defendant to answer on the new offense but did not sustain the petition to violate probation because there was nothing outside the Proposition 115 testimony to prove that the camera was in fact stolen. Over defense objection, the prosecution later re-alleged the same violation of probation, this time presenting additional witnesses, including the victim, who confirmed the theft of his property. The petition was sustained and defendant appealed. Held: The order revoking probation was reversed because collateral estoppel barred the second proceeding. In this case the threshold requirements of collateral estoppel were met – identical issues, actually litigated, necessarily decided, final and on the merits, and the party against whom preclusion was sought is the same as in the prior proceeding. At the first hearing the prosecution failed to assert the live witnesses were unavailable or to show good cause why testimonial hearsay should be allowed in lieu of live testimony. The prosecution could have appealed the decision not to violate defendant’s probation, but failed to do so; thus the order was final for collateral estoppel purposes. Further, application of issue preclusion is consistent with the underlying purposes of the doctrine to preserve the integrity of the judicial system, promote judicial economy and prevent undue harassment of defendants.