EARLY one morning a team of heavily armed police officers burst into the home of Eugene Mallory, an 80-year-old retired engineer in Los Angeles county. What happened next is unclear. The officer who shot Mr Mallory six times with a submachine gun says he was acting in self-defence—Mr Mallory also had a gun, though he was in bed and never fired it. Armed raids can be confusing: according to an investigation, the policeman initially believed that he had ordered Mr Mallory to “Drop the gun” before opening fire. However, an audio recording revealed that he said these words immediately after shooting him. Mr Mallory died. His family are suing the police.

Such tragedies are too common in America. One reason is that the police have become more militarised. Raids by Special Weapons and Tactics (SWAT) units used to be rare: according to Peter Kraska of Eastern Kentucky University there were only about 3,000 a year in the early 1980s. Now they are routine: perhaps 50,000 a year (see article).

These teams, whose members wear body armour and are equipped with military-style weapons, were originally intended to tackle only the most dangerous criminals, such as murderers or hostage-takers. Now they are most commonly used to serve search warrants in drug-related cases. The police raided Mr Mallory’s home, for example, because they thought they would find a methamphetamine factory there. Instead they found two marijuana plants, belonging to a stepson who had a California medical-marijuana licence.

Some of the uses to which SWAT teams are put defy belief. In Maryland paramilitary police have been sent to break up illegal poker games; in Iowa, to arrest people suspected of petty fraud; in Arizona, to crack down on cockfighting.

America’s courts tend to smile on SWAT tactics. They have ruled that police may enter a home without knocking if announcing their presence might give a criminal a chance to destroy evidence, for example by flushing drugs down the toilet. Such “no-knock” raids carry the advantages of surprise—and the disadvantages.

Having armed men burst into one’s home is terrifying. Startled citizens may assume they are being burgled—the “flash-bang” grenades that SWAT teams toss in to (temporarily) blind and deafen their targets tend to add to the confusion. Some people shoot back, with tragic consequences. Radley Balko, a campaigning journalist, has identified more than 50 innocent civilians who have been killed in SWAT raids.

Two factors have pushed the American police to militarise. First, thanks to the “war on terror”, there is plenty of money available for big weapons. Between 2002 and 2011 the Department of Homeland Security handed out a whopping $35 billion in grants to state and local police. In addition, the Pentagon supplies surplus military hardware to police forces at virtually no cost. That is why the quiet little town of Keene, New Hampshire has an armoured personnel carrier called a BearCat, which the local police chief said might be used to protect its pumpkin festival.

Second, the war on drugs creates perverse incentives. When the police find assets that they suspect are the proceeds of crime, they can seize them. Under civil asset-forfeiture rules, they do not have to prove that a crime was committed—they can grab first and let the owners sue to get their stuff back. The police can meanwhile use the money to beef up their own budgets, buying faster patrol cars or computers. All this gives them a powerful incentive to focus on drug crimes, which generate lots of cash, rather than, say, rape, which does not. This is outrageous. Citizens should not forfeit their property unless convicted of a crime; and the proceeds should fund the state as a whole, not the arm that does the grabbing.

Bang! Knock, knock...er, sorry, wrong house

The police do a difficult and dangerous job, and it is completely understandable that they do not wish to be outgunned by bad guys. A big show of force can sometimes deter criminals from starting a fight. And police departments are right to spend generously on defensive equipment such as body armour, which increases the chance that officers will come home alive.

Nonetheless, the militarisation of American law enforcement is alarming. The police are not soldiers. Armies are trained to kill the enemy; the police are supposed to uphold the law and protect citizens. They should use the minimum force necessary to accomplish those goals.

That does not mean getting rid of SWAT teams entirely. But it does mean restricting their use to situations where there are solid grounds to believe that the suspect involved is armed and dangerous. They should not be used to serve search warrants on non-violent offenders, or to make sure that strip joints are code-compliant, or in any circumstance where a knock on the door from a regular cop would suffice. The “war on drugs” is supposed to be a metaphor, not a real war.