Westchester’s district attorney is speaking out for the first time since the case was sealed against a teen driver who killed a Yonkers police officer a year ago.

DA Mimi Rocah said her office left “no stone unturned” but the state's "raise the age" law was the ultimate factor.

Under the law, the judge must transfer criminal cases against 16- and 17-year-olds charged with serious felonies unless there are certain aggravating factors.

In this case, prosecutors were unable to prove that – so the was case sealed and sent to family court.

Last Dec. 1, the then-16-year-old driver with a learner permit was speeding and crashed head-on with Detective Sgt. Frank Gualdino's patrol car, killing the 24-year veteran of the department.

Two months ago, a grand jury indicted one charge of criminally negligent homicide.

In a social media post last week, the Yonkers PBA said it was saddened and disgusted but not surprised.