In a move that could significantly change how the District’s court system handles teenage offenders, the D.C. attorney general has proposed legislation that would bar prosecutors from charging juvenile defendants as adults without a judge’s permission, even for the most heinous crimes.

If passed by the D.C. Council later this year and signed by Mayor Muriel E. Bowser (D), the bill, dubbed the Redefinition of Child Amendment Act, would strip the U.S. attorney’s office of its unilateral authority to prosecute 16- and 17-year-olds as adults in D.C. Superior Court.

Prosecutors in D.C. now have the power to file adult charges against youths in that age range in cases of alleged murder, forcible rape, first-degree burglary and armed robbery. And they often use that power: From the start of 2013 to last July, more than 250 defendants ages 16 and 17 in the city were sentenced to prison as adults, according to D.C. Attorney General Karl A. Racine’s office.

In announcing his proposal, Racine said he wants to keep more juveniles out of adult prisons and enhance opportunities for rehabilitation.

“This needed legislation would bring our justice system into alignment with long established scientific research that tells us the brain is not fully developed at ages 16 and 17, and that young people, even those who commit serious crimes, can learn and evolve into upstanding and valuable members of our community,” Racine said in a statement.

The bill, which the D.C. Council probably will begin considering in the fall, would not preclude the U.S. attorney’s office from handling 16- and 17-year-olds as adults. But it would make it more difficult for prosecutors to do so, by putting those alleged offenders in the same legal category as 15-year-old defendants.

No matter what crime a 15-year-old is charged with in the District, the case begins in juvenile court. A case of alleged murder, forcible rape, armed robbery or first-degree burglary can be transferred to adult court only if a prosecutor convinces a judge that there is no reasonable chance for the 15-year-old to be rehabilitated in the juvenile system. Prosecutors have a heavy burden of proof in that process.

By requiring the U.S. attorney’s office to bear that same burden in cases involving 16- and 17-year-olds, Racine said, his bill “would modernize the definition of ‘child’ to reflect modern science and common sense.” Under D.C. law, children younger than 15 cannot be prosecuted in adult court for any offense.

A spokesperson for acting U.S. attorney Channing D. Phillips did not respond to a request for comment on Racine’s proposal.

In one recent case, two juveniles arrested in February were charged as adults with first-degree murder in the killing of a teenager in Northwest Washington.

The defendants, Trey Prillerman and Nelfy Hernandez, were 16 and 17, respectively, at the time of the Aug. 10 homicide, in which 17-year-old Taijhon Wyatt Jr. was shot several times in an alley in the Brightwood Park neighborhood.

Prillerman and Hernandez, who are being held in the D.C. jail, have pleaded not guilty and are awaiting prosecution in Superior Court.

Unlike the adult system, juvenile court is focused entirely on rehabilitation, and punishment is not a factor in sentencing. Regardless of the crime, a defendant cannot be sent to prison. If convicted, the teenager is placed in the custody of the D.C. Department of Youth Rehabilitation Services. They can be confined to a juvenile detention facility, but only until they turn 21. Then they must be released.

“Children’s brains are not fully developed, making them more impulsive, reckless, and less able to understand the consequences of their actions than adults,” Racine said.

For example, two girls, ages 13 and 15, were charged as juveniles with murder, armed robbery and other offenses in the March 23 fatal carjacking of a food delivery driver in the District. The 66-year-old victim, who was struggling with the girls, was fatally injured when his car went out of control and crashed.

The 13-year-old could not be charged as an adult, and the U.S. attorney’s office did not try to move the 15-year-old’s case to adult court.

Both pleaded guilty to reduced charges in juvenile court in a deal with prosecutors.

At the 15-year-old’s sentencing last month, a judge in juvenile court put her in the custody of the youth agency, which could release her even before her 21st birthday if she is deemed to be rehabilitated. The 13-year-old is scheduled to be sentenced Tuesday.

D.C. Council member Charles Allen (D-Ward 6), chairman of the Committee on the Judiciary and Public Safety and a supporter of juvenile sentencing reform, said it is too soon to predict how Racine’s legislation will fare in the council.

But he said he agrees with the bill’s concept.

“It’s about the idea of, let’s have our courts treat kids as kids,” Allen said. “That’s the underlying approach here, and I think it’s the right one.”