#A-train derailer latest case of NYC’s system failing to protect the public

Demetrius Harvard was reportedly “smiling” as that Manhattan A-train flew off the rails Sunday morning, sideswiping at least 10 steel beams and tearing a huge chunk of metal off one car. It was another failure of the systems that are supposed to protect New Yorkers from sickos.

Harvard is accused of tossing metal construction debris onto the tracks at the West 14th station as the train pulled into the station. The derailment did nearly $1 million in damage, the MTA says. Luckily, only three people were injured — none killed.

So on Monday night, he was held in lieu of $50,000 cash bail at his arraignment in Manhattan Criminal Court. He was charged with assault, criminal tampering, reckless endangerment, criminal mischief and unlawful interference with a railroad train.

But he should’ve already been in custody: He was arraigned earlier in the month on one count of misdemeanor criminal mischief for allegedly striking an MTA bus with a metal street barricade and shattering two windows.

Manhattan prosecutors didn’t ask for bail then, and Harvard was granted supervised release — even though he already had an open bench warrant for failing to show up to court on a March 2019 case for threatening two staffers at a Boost store.

New Yorkers need criminal-justice and mental-health systems that protect the public from such threats, whether the perps are demented or just vicious. Yet state and city laws increasingly push for their release, even after they’ve repeatedly proven dangerous.

It’s a recipe for punishing the innocent.