37Punishment of persistent offenders.
(1)No person shall be sentenced by a court to preventive detention or corrective training.
(2)Where an offender is convicted on indictment of an offence punishable with imprisonment for a term of two years or more and the conditions specified in subsection (4) of this section are satisfied, then, if the court is satisfied, by reason of his previous conduct and of the likelihood of his committing further offences, that it is expedient to protect the public from him for a substantial time, the court may impose an extended term of imprisonment under this section.
(3)The extended term which may be imposed under this section for any offence may exceed the maximum term authorised for the offence apart from this section if the maximum so authorised is less than ten years, but shall not exceed ten years if the maximum so authorised is less than ten years or exceed five years if the maximum so authorised is less than five years.
(4)The conditions referred to in subsection (2) of this section are:—
(a)the offence was committed before the expiration of three years from a previous conviction of an offence punishable on indictment with imprisonment for a term of two years or more or from his final release from prison after serving a sentence of imprisonment, corrective training or preventive detention passed on such a conviction; and
(b)the offender has been convicted on indictment on at least three previous occasions since he attained the age of twenty-one of offences punishable on indictment with imprisonment for a term of two years or more; and
(c)the total length of the sentences of imprisonment, corrective training or preventive detention to which he was sentenced on those occasions was not less than five years and—
(i)on at least one of those occasions a sentence of preventive detention was passed on him; or
(ii)on at least two of those occasions a sentence of imprisonment (other than a suspended sentence which has not taken effect) or of corrective training was so passed and of those sentences one was a sentence of imprisonment for a term of three years or more in respect of one offence or two were sentences of imprisonment each for a term of two years or more in respect of one offence.
(5)Where an extended term of imprisonment is imposed on an offender under this section, the court shall issue a certificate (hereafter in this Act referred to as " an extended sentence certificate ") stating that the term was so imposed.