(a) A persistent felony offender is a person, other than a persistent violent felony offender as defined in section 70.08, who stands convicted of a felony after having previously been convicted of two or more felonies, as provided in paragraphs (b) and (c) of this subdivision.

(b) A previous felony conviction within the meaning of paragraph (a) of this subdivision is a conviction of a felony in this state, or of a crime in any other jurisdiction, provided:

(i) that a sentence to a term of imprisonment in excess of one year, or a sentence to death, was imposed therefor; and

(ii) that the defendant was imprisoned under sentence for such conviction prior to the commission of the present felony; and

(iii) that the defendant was not pardoned on the ground of innocence; and

(iv) that such conviction was for a felony offense other than persistent sexual abuse, as defined in section 130.53 of this chapter.

(c) For the purpose of determining whether a person has two or more previous felony convictions, two or more convictions of crimes that were committed prior to the time the defendant was imprisoned under sentence for any of such convictions shall be deemed to be only one conviction. 2. Authorized sentence. When the court has found, pursuant to the provisions of the criminal procedure law, that a person is a persistent felony offender, and when it is of the opinion that the history and character of the defendant and the nature and circumstances of his criminal conduct indicate that extended incarceration and life-time supervision will best serve the public interest, the court, in lieu of imposing the sentence of imprisonment authorized by section 70.00, 70.02, 70.04, 70.06 or subdivision five of section 70.80 for the crime of which such person presently stands convicted, may impose the sentence of imprisonment authorized by that section for a class A-I felony. In such event the reasons for the court's opinion shall be set forth in the record.