Here’s an interesting article.  The median age worldwide for criminal responsibility is 14.  The United States varies by state and about one third use criminal capacity tests to determine a child’s culpability.

Like most things: it’s complicated.

The article points to a 12 year old male child who killed a 10 year old girl and only got three years of  incarceration.   There was a public outcry in the local area.  Apparently, this and the increase of juveniles committing serious crimes across the country, such as murder, is on the rise.

Source: China lowers age of criminal responsibility to 12 from 14 | South China Morning Post