Assembly Speaker Carl Heastie demands proof that tougher penalties deter crime. Seriously.

Facing public outrage (including our contempt) over his first remarks on the issue, Heastie doubled down Tuesday, insisting, “I don’t believe, in the history of increasing penalties, has that ever been the reason that crime has gone down” — and “I’d love somebody to give me an example as to when that happened.”

Uh, just one? We won’t even break a sweat.

As Manhattan Institute crime expert Rafael Mangual documents in The Post, there’s a ton of compelling evidence that “harsher criminal penalties can and do deter crime.”

He cites, for instance, a study showing that California’s three-strikes law cut felony arrests among those with two strikes by as much as 20%.

Another study found that including incarceration among the penalties for court-fine scofflaws made payments more likely.

Not to mention the indisputable fact that anyone locked up for longer can’t reoffend during that time.

The likelihood of being arrested and locked up is also critical: When Mayors David Dinkins and Rudy Giuliani boosted the number of city cops nearly 30% — from 31,000 to 40,000 — major felonies plunged, from 430,460 in 1993 to 162,064 by 2001.

Murders those years went from 1,927 to 649 — a 66% drop — and kept falling, to 292 in 2017, a whopping 87% off the 1990 high of 2,262.

Broken Windows policing, i.e., cracking down on minor crimes, also helped.

You just can’t have a stronger cases for consequences than that.

Alas, crime began ticking up again after the city and state began weakening enforcement, handcuffing cops and prosecutors and relaxing consequences for criminals.

When Mayor Bill de Blasio and the state opened the prison gates during COVID, and cashless bail took effect in 2020, murders soared — to 488 by 2021, a 67% spike from just four years earlier.

Retail thefts (and the risk of violence to workers) are now off the charts — up more than 6.5%, to 14,910, this year alone, over the same period in 2023.

Hence the push to beef up penalties for violent shoplifters to protect retail workers.

“How do you deter crime except by penalty?” fumed Coalition to Save our Supermarkets head Nelson Eusebio in The Post of Heastie’s denialism “It’s open season on retail workers in the city.”

We get it: The speaker feels he has to pander to deranged progressives by blocking measures to protect bodega workers and so on.

But he sure looks the fool by pretending he’s never seen the evidence that policies he opposes actually work.