The binding legal principles established are: (1) Before imposing a prescribed minimum sentence under section 51 of the Criminal Law Amendment Act, a sentencing court is obliged to investigate and determine whether substantial and compelling circumstances exist that justify a deviation from the prescribed sentence; (2) It is incumbent upon a court in every case to assess, upon consideration of all circumstances of the particular case, whether the prescribed sentence is proportionate to the particular offence, which consists of all factors relevant to the nature and seriousness of the criminal act itself, as well as all relevant personal and other circumstances relating to the offender; (3) If a court is satisfied that a lesser sentence is called for in a particular case, the court is bound to impose that lesser sentence; (4) While youthfulness is not per se a substantial and compelling factor for offenders who have attained the age of 18 years, it often will be, particularly when other factors are present, and a court cannot lawfully discharge its sentencing function by disregarding youthfulness when imposing life imprisonment; (5) A sentencing court must receive sufficient evidence to inform itself as to the proper sentence, and if parties fail to adduce such evidence, the court is obliged to take steps to receive it; (6) The traditional factors considered when imposing sentence must still be taken into account in determining whether substantial and compelling circumstances are present; and (7) There are different degrees of seriousness even in cases where life imprisonment is the prescribed minimum sentence, and courts must consider all factors before imposing sentence.