(1) Subject to the provisions of ORS 161.737, the maximum term of an indeterminate sentence of imprisonment for a dangerous offender is 30 years, if because of the dangerousness of the defendant an extended period of confined correctional treatment or custody is required for the protection of the public and one or more of the following grounds exist:
(a) The defendant is being sentenced for a Class A felony and the defendant is suffering from a severe personality disorder indicating a propensity toward crimes that seriously endanger the life or safety of another.
(b) The defendant is being sentenced for a felony that seriously endangered the life or safety of another, the defendant has been previously convicted of a felony not related to the instant crime as a single criminal episode and the defendant is suffering from a severe personality disorder indicating a propensity toward crimes that seriously endanger the life or safety of another.
(c) The defendant is being sentenced for a felony that seriously endangered the life or safety of another, the defendant has previously engaged in unlawful conduct not related to the instant crime as a single criminal episode that seriously endangered the life or safety of another and the defendant is suffering from a severe personality disorder indicating a propensity toward crimes that seriously endanger the life or safety of another.
(2) As used in this section, “previously convicted of a felony” means:
(a) Previous conviction of a felony in a court of this state;
(b) Previous conviction in a court of the United States, other than a court-martial, of an offense which at the time of conviction of the offense was and at the time of conviction of the instant crime is punishable under the laws of the United States by death or by imprisonment in a penitentiary, prison or similar institution for a term of one year or more; or
(c) Previous conviction by a general court-martial of the United States or in a court of any other state or territory of the United States, or of the Commonwealth of Puerto Rico, of an offense which at the time of conviction of the offense was punishable by death or by imprisonment in a penitentiary, prison or similar institution for a term of one year or more and which offense also at the time of conviction of the instant crime would have been a felony if committed in this state.
(3) As used in this section, “previous conviction of a felony” does not include:
(a) An offense committed when the defendant was less than 16 years of age;
(b) A conviction rendered after the commission of the instant crime;
(c) A conviction that is the defendant’s most recent conviction described in subsection (2) of this section, and the defendant was finally and unconditionally discharged from all resulting imprisonment, probation or parole more than seven years before the commission of the instant crime; or
(d) A conviction that was by court-martial of an offense denounced only by military law and triable only by court-martial.
(4) As used in this section, “conviction” means an adjudication of guilt upon a plea, verdict or finding in a criminal proceeding in a court of competent jurisdiction, but does not include an adjudication which has been expunged by pardon, reversed, set aside or otherwise rendered nugatory.