Oregon Revised Statutes Procedure in Criminal Matters Generally § 136.434

(1) Except as provided in ORS 813.328, if an accusatory instrument or the written notice described in ORS 136.765 (2) alleges that the defendant has previously been convicted of an offense, the defendant may challenge the validity of the previous conviction by filing a notice of the defendant's intent to do so. The notice must:

(2) The validity of the previous conviction shall be determined by the court before trial. At the hearing on the defendant's challenge:

(3) If the court determines that the defendant was not previously convicted of the offense that is the subject of the challenge or that the previous conviction is not valid, the court shall enter an order prior to trial that so provides and excludes evidence of the previous conviction. The state may appeal from the order pursuant to ORS 138.060 (1)(c) or (2)(a).

(4) If the court determines that the defendant previously was convicted of the offense and that the conviction is valid, or if the defendant does not file and serve a notice under subsection (1) of this section, the previous conviction shall be admitted at trial or, if the previous conviction is relevant to an enhancement fact described in ORS 136.770 (4) or 136.773 (1), during the sentencing phase of the proceeding. If the previous conviction is admitted, the defendant may dispute whether the defendant previously was convicted of the alleged offense but may not challenge the validity of the conviction. If the previous conviction is a material element of the charged offense or is an enhancement fact, the state must prove the previous conviction beyond a reasonable doubt unless the defendant stipulates to the fact of the previous conviction in accordance with ORS 136.433.

(5) For purposes of this section, a previous conviction is not valid if: