What is the test for determining a disproportionate punishment for a minor who sexually assaulted a minor?

fundamental notions of human dignity.' [Citation.] An examination of the nature of the offense and of the offender, '"with particular regard to the degree of danger both present to society"' is particularly relevant in determining this issue. [Citation.] In assessing the nature of the offense, a court should consider the circumstance of the particular offense such as the defendant's motive, the way the crime was committed, the extent of his involvement and the consequences of his acts. [Citation.] In analyzing the nature of the offender, a court should consider his 'age, prior criminality, personal characteristics, and state of mind.' [Citation.] '[A] punishment which is not disproportionate in the abstract is nevertheless constitutionally impermissible if it is disproportionate to the defendant's individual culpability.' [Citation.]" (People v. Felix (2003) 108 Cal.App.4th 994, 1000.)