Murder at 17 = juvenile sentence.
Murder at 18 = you are going to the clink with the big boys.
It’s called being an adult, and it isn’t hard to understand at all.
17 and sometimes younger can be charged as adults for heinous crimes.
Age of consent in many states is 16. Go back a hundred years and the laws were even younger.
This is not about being an “adult”, since a 16 year old may legally consent to sex. 18 is adult you say, but they may not drink alcohol. They die as Soldiers for us though.