Both the killing of an unarmed black teenager and the vicious response to protesters have shown Americans the dangers of militarised policing, writes

Over the past week Americans have been treated to pictures of police in woodland camouflage pointing assault rifles at protesters. The protesters, nearly all African-Americans, march through a Missouri suburb with their arms raised to show they are not carrying weapons. They are demanding to know why a police officer killed an unarmed black teenager there last Saturday.

The St Louis County Police Chief claims an officer shot Michael Brown when he and another teenager attacked him as he got out of his police truck and tried to wrest his gun from him. Eyewitnesses say the officer assaulted Brown after he disobeyed his order to lie down on the sidewalk. Witnesses agree that the officer shot Brown as he was running away. This happened in broad daylight in Ferguson, a predominantly black suburb of St Louis.

Brown is one of four unarmed black men to have died at the hands of police in the United States in the last month. In each case, police and eyewitnesses dispute the circumstances under which the killing took place. But each case involves police assumptions about black male criminality, the same assumptions that led Florida police to believe George Zimmerman's story that Trayvon Martin attacked him.

Police only began a proper investigation of Martin's death after community protests in Sanford, Florida. There have also been protests in Ferguson, and the police response to them has drawn national attention. In the course of five days, police have fired on protesters with rubber bullets, tried to disperse protesters from their own front yards, forbade onlookers from taking photos or video footage, and used tear-gas against protesters and media alike.

St Louis County Police have been dressed in camouflage and riot gear, armed with automatic weapons and covered by snipers. Their actions have been so disproportionate that Missouri Governor Jay Nixon has put the State Highway Patrol in charge of future protests. Both the killing of Brown and the vicious response to protesters have shown Americans the dangers of militarised policing.

In the early 1990s rates of violent crime began to drop steeply across the United States. Crime has continued to drop, and is at its lowest rate in decades today. The response to crime, however, continues to get more extreme. It was in the early nineties, at the height of a panic about urban (i.e. black) "super-criminals", that Congress passed legislation allowing the transfer of retired military equipment to local police departments. For little or no cost, police obtained machine guns, grenade launchers, military aircraft and mine-resistant armoured vehicles.

Procured for use against drug lords, terrorists and hostage-takers, most police departments have little purpose for these items. In June, the New York Times reported that heavily-armed SWAT teams have conducted nightclub raids in Louisiana to enforce liquor laws, and stormed barbershops in Florida to bring charges of "barbering without a licence."

This kind of overkill has attracted outrage from both the left and the right of American politics. Innocent people have died in botched raids. But at a time when local services of all kinds face crippling shortages of funds, free military equipment is an attractive option for police who can no longer afford traditional patrols.

Troops in combat expect to use lethal force to achieve military objectives, and to defend themselves from others who are trying to kill them. What message does it send to communities when police are armed and outfitted in the same way? And what message does it send to the police themselves?

Everyone understands that it is extremely dangerous to attack a police officer, especially one carrying a gun. This is why even hardened criminals rarely attempt it, except under the most desperate circumstances. The idea that an unarmed, college-bound teenager would do so seems absurd. But if police are equipped to fight an insurgency, at least some of them are going to see insurgents everywhere.

Heavily armed police accelerate the broader American gun culture. Police violence has a long history of provoking American citizens to arm themselves. The Second Amendment had no greater champions than the Black Panther Party of the 1960s and 1970s, who would patrol city streets with guns to deter police brutality against black people. The Panthers opposed gun control because they saw it as an attack on black self-defence against the state. At a time when even the NRA favoured extensive gun control, the Panthers were the most militant gun rights activists in America.

If any group of African Americans attempted the same tactics today, there would be a full-blown invasion of their communities by paramilitary police. The right to keep and bear arms is now an extension of white privilege. We can expect many more deaths in defence of that privilege.

This article was originally published at ABC The Drum