The nine men now on death row in New Jersey’s prisons will soon be spared if, as expected, the state’s Legislature enacts a ban on capital punishment – a proposal advanced by the state’s Death Penalty Study Commission.

For the record, New Jersey hasn’t actually executed anyone since 1963, though the state nominally restored the death penalty in 1982.

And the panel’s 127-page report – based heavily on public polling data and the comparative costs of executions vs. life imprisonment – is far from compelling.

Jersey’s Legislature created the commission in late 2005; the panel then held a series of public meetings before calling for scrapping the death penalty in favor of life imprisonment without the possibility of parole in a maximum-security prison.

That’s all well and good – if the state could guarantee that “life without parole” means life without parole.

But, as New Jerseyans have good reason to know, there is no such thing.

Case in point: the state’s most notorious killer, Thomas Trantino, who coldly murdered two cops in 1963.

In begging the jury at his trial to spare his life, Trantino’s lawyer insisted there was no chance he’d ever be set free. “Isn’t life without parole enough?” his lawyer asked.

The jury decided it wasn’t; Trantino was sentenced to die – only to be spared when the U.S. Supreme Court outlawed capital punishment in 1972.

Then, in 2002, the Garden State’s own Supreme Court decided that life without parole was too much – and ordered the killer freed from his supposed life-without-parole sentence.

Little wonder, then, that the sister of one of Trantino’s victims isn’t convinced. “I don’t have a problem with life without parole if it’s really life without parole,” said Patricia Tedesco, whose brother Gary was gunned down by Trantino. “But they always find a way out.”

The commission’s report – which Gov. Corzine and leaders of the Democratic-controlled Legislature say they plan to enact – comes amid a nationwide weakening of support for the death penalty.

There’s a reason for this, of course – violent crime has fallen by record levels since the period a dozen years ago when the public clamor for capital punishment helped George Pataki defeat Gov. Mario Cuomo in New York.

But crime levels, sad to say, are cyclical. And few are the law-enforcement officials who believe the current downturn in violent crime can be sustained indefinitely. Indeed, across the nation there has been a slow – but steady – uptick in the murder rate.

If that figure holds, or increases, public attitudes toward capital punishment – which play a large part in the ongoing national debate – may shift yet again.

But the best crime-fighting policy is not determined by polls or cost data. And until there is an ironclad guarantee that courts will not interfere with life-without-parole sentences, the death penalty should remain an available option in the most heinous crimes.