The Advisory Commission on Prison Terms and Parole Standards and the State Board of Parole and Post-Prison Supervision shall provide, in rules adopted under ORS 144.785, that, in the case of a crime involving a physical or sexual assault, a victim’s particular vulnerability to injury in such case due to the victim’s youth, advanced age or physical disability, shall constitute an aggravating circumstance justifying a variation from the range of duration of imprisonment otherwise applicable in the case. [1985 c.767 §3]