A week ago, Gov. Chris Sununu, as promised, vetoed House Bill 455, which would repeal the use of the death penalty in New Hampshire. Lawmakers in both chambers of the Legislature easily passed the bill earlier this session, and it now lands back at their feet.

They should vote to override the veto and do away with capital punishment in the Granite State once and for all.

Sununu, in announcing his veto, turned to an emotional appeal, tying the move to the lone capital case in recent state history: the murder of a Manchester police officer. To buttress his argument, he relied on the family of the slain officer and police spokesmen, who regularly back the death penalty — especially in cases involving police deaths.

“If a repeal occurs, there will be no penalty for murdering a police officer,” said Mark Chase, president of the New Hampshire Chiefs of Police Association, at last Friday’s veto media event at the Michael Briggs Community Center in Manchester where, accompanied by the family of Officer Briggs, the chief of the Manchester police also spoke in favor of capital punishment — specifically citing Michael Addison, who shot and killed Briggs during a robbery in 2006. Never mind that the bill Sununu vetoed was crafted purposely to not apply to Addison.

We can’t fault their anger; what happened to Briggs was terrible and Addison surely ought to be punished for it. What Mrs. Briggs and the Manchester police officers are seeking, though, isn’t justice; it’s vengeance. Killing Michael Addison wouldn’t bring Michael Briggs back, nor would it ease their loss. At least, that’s what family members of other murder victims have said, both to Sununu and lawmakers.

It’s old-school, eye-for-an-eye, life-for-a-life wrath — the type advocated in the Old Testament. But even many denominations that once backed the death penalty for that reason now oppose it as nothing more than state-sanctioned murder. “The death penalty neither deters others, nor brings this perpetrator to understanding, but instead, in the worst of ironies, publicly validates the very act of taking a human life,” notes Bishop Peter A. Libasci, head of the Diocese of Manchester.

Sununu’s avowed strong support of the opinions of law enforcement — especially regarding their safety — was undercut when he first took office and pushed hard for legislation allowing almost anyone to carry a concealed firearm in public with a permit, something police chiefs across the state said puts their officers at risk.

And Chase is wrong. Those who kill a police officer would still face a penalty — the same penalty any murderer would face. We’d guess the courts and juries will still consider the seriousness of killing a police officer, but studies have shown capital punishment is not a deterrent, and that goes for crimes against law enforcement, too.

Attitudes toward capital punishment have come a long way. Even many conservatives who once backed the death penalty now oppose it simply on economic terms. It costs far more to kill a convicted murderer than to keep him or her locked up for life. That’s largely due to the extensive appeals process involved, but those appeals are necessary as long as capital punishment exists. As science has advanced, we’ve seen case after case in which those sentenced to death were ultimately found to be wrongly convicted. Our legal system simply isn’t perfect, and the chance that an innocent person will be murdered by the state is too great.

There may always be cases where it’s clear the defendant is guilty of a heinous act. But the law can’t be applied based on individual circumstances. Many of those proven not guilty were, at one point, considered guilty beyond a reasonable doubt.

Now that Gov. Sununu has vetoed HB 455, the House is set to take up a possible override May 23, with the Senate to follow. Both should stick to their guns.

The cost of capital punishment is too high to be allowed. It strains the state’s legal resources. It won’t prevent anyone from murdering in the future. Most importantly, it makes all of us a party to murder.