Oregon Revised Statutes Procedure in Criminal Matters Generally § 136.773

(1) When an enhancement fact relates to the defendant, the court shall submit the enhancement fact to the jury during the sentencing phase of the criminal proceeding if the defendant is found guilty of an offense to which the enhancement fact applies unless the defendant makes a written waiver of the right to a jury trial on the enhancement fact and:

(2) If the defendant makes the election under subsection (1)(b) of this section and is found guilty during the trial phase of the criminal proceeding, the enhancement fact shall be tried during the sentencing phase of the proceeding.

(3) If there is more than one enhancement fact relating to the defendant and the defendant does not admit to all of them, the defendant shall elect to try to the jury or to the court all enhancement facts relating to the defendant to which the defendant does not admit.

(4) If two or more defendants are being tried in the same criminal proceeding, each defendant shall make the elections required by this section.

(5) Unless the defendant waives the right to a jury trial on enhancement facts related to the defendant, the sentencing phase shall be conducted in the trial court before the jury following a finding of guilt by the jury. If for any reason a juror is unable to perform the function of a juror, the court shall dismiss the juror from the sentencing phase and draw the name of one of the alternate jurors. The alternate juror then becomes a member of the jury for the sentencing phase notwithstanding the fact that the alternate juror did not deliberate on the issue of guilt. The court may allow the substitution of an alternate juror only if the jury has not begun to deliberate on the issue of an enhancement fact.