255Extended sentence of detention: availability
(1)An extended sentence of detention under section 254 is available where a court is dealing with an offender for an offence if—
(a)the offence—
(i)is a specified offence (see section 306(1)), and
(ii)is listed in the table in section 249(1) (sentence of detention under section 250: availability),
(b)the offender is aged under 18 when convicted,
(c)the court is of the opinion that there is a significant risk to members of the public of serious harm occasioned by the commission by the offender of further specified offences (see section 308),
(d)the court is not required by section 258(2) to impose a sentence of detention for life under section 250, and
(e)if the court were to impose an extended sentence, the term that it would specify as the appropriate custodial term (see section 256) would be at least 4 years.
(2)The pre-sentence report requirements (see section 30) apply to the court in relation to forming the opinion referred to in subsection (1)(c).