touching is 4th degree in michigan. that would be pretty bad to kill someone because he touches a 13 yr old. There would have to be some clarification on Michigan's sex offender list before something like that would work here.
We just had a local 18 yr old kid get 10 to 20 in prison because a girl at a party brought ecstasy and took it herself. Then she went to the cops. She was 16 and he was 18...He's now going to be on the "list" which means nothing here.
Unfortunately, justice is one of the first things that suffer, when people act on their emotions. I'm sure it would bother someone,later in life, if they knew the guy that touched them 40 yrs ago, got executed for it.
10-20 seems excessive for that case as you described it.