You know what I'm talking about. a 4 year old is a toddler, not a youth/teen.
By the age we're talking about here even a badly raised teen must be held responsible for his/her actions.( we can argue till we're blue in the face over what the "cutoff" age should be but for certain things its gotta be lowered from 18 or whatever it is by country).
If you have a more effective solution I'm all ears.
No, I have no easy solutions. However, even your position has an inherent problem that will only reduce this issue, not eliminate it. How do you set your cutoff? What separates a youth/teen from a toddler? No matter what age we set (like 18) there will always be cases like this where the kid needs either more or less punishment due to their "mental age." Thus, we are left with the situation we have now - deciding individual crimes on a case-by-case basis depending on the kid. Which will inevitably produce bad judgments over time, that we can all get upset about.
I don't see any way to alleviate this basic problem.