NEW HAMPSHIRE has just failed to abolish the death penalty—by one vote. Given that the Granite State has not actually executed anyone since 1939, you might think this doesn’t matter much. But, obviously, it matters to the one man on death row in New Hampshire, a cop-killer called Michael Addison. It matters, also, to the broader campaign to scrap capital punishment in America. And despite the setback in New Hampshire, the abolitionists are slowly winning. America is unusual among rich countries in that it still executes people. It does so because its politicians are highly responsive to voters, who mostly favour the death penalty. However, that majority is shrinking, from 80% in 1994 to 60% last year. Young Americans are less likely to support it than their elders. Non-whites, who will one day be a majority, are solidly opposed. Six states have abolished it since 2007, bringing the total to 18 out of 50. The number of executions each year has fallen from a peak of 98 in 1999 to 39 last year (see article).

Many people regret this. Some feel that death is the only fitting punishment for murderers: that it satisfies society’s need for retribution. Some find a religious justification, such as the line in Exodus that calls for: “life for life, eye for eye, tooth for tooth”. Such appeals to emotion or faith are hard to answer, although the Bible also has passages about not casting the first stone, and many conservative evangelicals have ended up in the odd position of prizing life when it comes to abortion, but not when it comes to prisoners (the Catholic church is pro-life on both counts). However, in a secular democracy a law of such gravity must have some compelling rational justification, which the death penalty does not.

Its advocates insist that it deters murderers, thereby saving lives. If this were true, it would be a powerful argument, but there is scant evidence that it is. The murder rate is far higher in America than in the European Union, which has no death penalty. It is also higher in American states that carry out executions than in states that do not. Granted, some studies have found that, if you control for other factors that also influence crime rates, you can make the case that each execution prevents three murders, or five, or even 18. But such studies are based on thin data and questionable assumptions. There were nearly 15,000 murders in America in 2012. The chance of any individual killer being executed is thus microscopic—and distant, since the appeals process can grind on for decades.

Against the death penalty’s uncertain benefits must be set its certain defects. Juries, being human, are fallible. If they jail an innocent man he can be freed and compensated, but he cannot be brought back to life. Since the Supreme Court lifted its suspension of the death penalty in 1976, there are no proven cases where America has executed an innocent. But there are at least ten that look horribly like it. Cameron Todd Willingham, for example, was put to death for starting a deadly fire, although experts blamed faulty wiring (see article).

Vengeance is mine, says the Lord

To avoid miscarriages of justice, America has erected elaborate safeguards. Capital cases are subject to multiple appeals; teams of lawyers haggle over them for years. An unintended consequence of this is that executing a murderer is now perhaps three times more expensive than locking him up for life. The money spent on the machinery of death would probably do more to improve public safety if it were spent on better policing, to catch the ones who currently get away. Put simply, the death penalty looks like a colossal waste of taxpayers’ money, which conservative politicians would normally denounce.

Of late, abolitionists have put a lot of effort into lawsuits to make it harder for states to get hold of the drugs used in lethal injections. This is more likely to delay executions than to end them. A more democratic approach would be to persuade voters that capital punishment is not just barbaric but also costly, ineffective and prey to human error, and that they should therefore back politicians who oppose it. That is how New Mexico, Oregon, Illinois, Connecticut, Maryland, Colorado and Washington stopped or suspended it. New Hampshire will try again. State by state, abolitionists will prevail. America is a nation founded on the principle that governments should not be trusted with too much power; that should include the power to strap people to a gurney and poison them.