Connecticut Gov. Dannel Malloy wants to raise the maximum age for the juvenile justice system to 20, up from 17.

The idea means someone who commits a crime at 20 years old would not be tried as an adult, barring special circumstances. That's already a change that would be unheard of in the US — Connecticut would be the first in the nation to do this, the Connecticut Mirror reported. (Although not the first in the world — Germany, for one, already by and large treats people as juveniles up to the age of 20.)

But Malloy went even further, suggesting that the justice system should figure out a more lenient, alternative ways to handle those under 25 years old who commit less serious offenses.

These might seem like extreme ideas — and they certainly are outside the norm in the US. But here's the thing: The research and experts increasingly agree that the juvenile justice age is far too low. In fact, if anything, the research suggests Malloy's plan does not go far enough.

Raising the juvenile justice age to 20 — or even 25 — isn't as ridiculous as it sounds

The juvenile justice system was set up under the idea that some people are too young — and their brains aren't developed enough — to be held wholly accountable for their actions, so a more rehabilitative and less punitive approach makes more sense. But the states adopted a fairly arbitrary age cutoff for the juvenile system: 18. And with more research showing that people's brains don't stop developing until at least their mid-20s, Malloy said it's time to raise the juvenile age.

This is actually a very popular idea among some criminal justice reformers. Earlier this year, the Washington Post ran a piece by the Harvard Kennedy School's Vincent Schiraldi and Bruce Western proposing raising the juvenile justice age to 21, meaning a 21-year-old offender would generally be tried as a minor.

But Schiraldi and Western actually included a big caveat: Although this already seems like a big shift, brain science suggests we should go even further:

Research in neurobiology and developmental psychology has shown that the brain doesn't finish developing until the mid-20s, far later than was previously thought. Young adults are more similar to adolescents than fully mature adults in important ways. They are more susceptible to peer pressure, less future-oriented and more volatile in emotionally charged settings. Furthermore, adolescence itself has become elongated compared with that of previous generations. Today's young people finish college, find jobs, get married and leave home much later than their parents did. Just 9 percent of young adults were married in 2010, compared with 45 percent in 1960.

In some ways, the criminal justice stats reflect the science of development: 78 percent of 18- to -24-year-olds released from prison are rearrested, and about half go back to prison within three years — the highest rate among any age group, according to Schiraldi and Western.

Again, the research shows this is likely due to a bunch of biological factors that hold back some people — even those we consider young adults — in terms of maturation. Here's how MIT's Young Adult Development Project described the latest research:

According to recent findings, the human brain does not reach full maturity until at least the mid-20s. (See J. Giedd in References.) The specific changes that follow young adulthood are not yet well studied, but it is known that they involve increased myelination and continued adding and pruning of neurons. As a number of researchers have put it, "the rental car companies have it right." The brain isn't fully mature at 16, when we are allowed to drive, or at 18, when we are allowed to vote, or at 21, when we are allowed to drink, but closer to 25, when we are allowed to rent a car.

So if we now know that to be true, can we really justify punishing someone with a less developed brain in the same way as someone with a more developed brain?