Rupert Cornwell: The murderous demon of race still stalks this land

Out of America: The killing of Trayvon Martin has again ruthlessly exposed the faultlines that underlie Obama-era America

Every so often in America there comes a tragedy that exposes the country's most sensitive faultlines: a shooting rampage on a university campus, a convicted killer executed when common sense suggests the evidence against him is horribly flawed, the murder by pro-life extremists of a doctor who has carried out abortions. And now we have the death of Trayvon Martin.

The basic facts of what happened are by now well known. A 17-year-old student of unblemished reputation, Martin was shot dead by a self-appointed local crime watch vigilante named George Zimmerman, as he walked home through an upscale neighbourhood in Sanford, Florida on the night of 26 February, carrying nothing more menacing than a mobile phone, a bottle of iced tea and a bag of fruit-flavoured sweets.

At first, little attention was paid. The Florida newspapers naturally reported on the incident, but national media coverage was perfunctory at best. Today, thanks to social media, Trayvon Martin is the biggest news story in the US, bigger than tomorrow's Supreme Court hearings on Obamacare that could decide the fate of an American presidency, bigger even than the case of the US army sergeant Robert Bales, accused of massacring 17 Afghan villagers.

But the senseless death of a single black teenager deserves all its prominence, and more. In terms of exposing social faultlines, it virtually runs through the card. Once again, we are reminded of the foolish laxity of US firearms legislation, in obeisance to the mighty gun lobby. (Just last month Virginia, where the country's worst campus massacre took place in 2007, repealed a law that sought to restrict citizens to the purchase of just one handgun per month.)

Once again, the dangers of America's proliferating "stand your ground" laws are plain to see. Florida was among the first states to adopt one, complete with the right to use lethal force if required, but now 23 others (mainly but not exclusively in the south and west) have similar self-defence legislation on their books, most albeit with a "duty to retreat" provision requiring confrontation to be avoided if possible. In fact, such laws are frequently an invitation for people with a grievance to take the law into their own hands, and then claim they acted in self-defence. To prevail, prosecutors must prove otherwise, no easy task when their chief witness is dead. And, of course, above all, there's race.

The Trayvon Martin affair teems with questions. Why was an unarmed teenager shot, when by all accounts he was minding his business and threatening no one? Why has Zimmerman not been arrested? Why does Florida have a self-defence law at all? Why – until national outrage forced them to change their mind – did the police fail to investigate? The answer to all these questions, in one degree or another, is race.

Some have likened the case to that of Emmett Till, the black teenager hunted down, beaten and murdered in Mississippi in 1955 because he had allegedly whistled at a white woman. Till's death was a galvanising moment in the struggle for civil rights, but even now events almost as dreadful occur. Only four days ago, in that same Deep South state, 19-year-old Deryl Dedmon was sent to prison for life for driving his truck over a black man in a car park last summer and killing him, after Dedmon and a couple of white friends had gone out searching for black men to attack.

However, nothing so far suggests that George Zimmerman perpetrated a deliberate hate crime. Exactly what happened on 26 February is still unclear: he claimed to police he was acting in self-defence, but other evidence indicates that Martin, unarmed and scared, was running away from his pursuer before he was shot. Zimmerman (who is Hispanic and has some black relatives) does not seems to have been an overt racist, rather a neighbourhood watch volunteer of a zealotry bordering on paranoia.

But without reflexive racial assumptions, the tragedy surely would not have occurred. A black kid in a prosperous white neighbourhood, especially when it's raining and his jacket hood is pulled over his head, is automatically assumed to be up to no good. Indeed, Jesse Jackson himself once confessed: "If I'm walking down a dark street late at night and I see that the person behind me is white, I subconsciously feel relieved." Trayvon Martin, alas, wasn't white.

Imagine, though, the attitude of the Florida police had the skin colours been reversed: that a black neighbourhood watch captain had shot dead an unarmed white student. Who can believe the black man would not now be behind bars, held without bail, charged with murder? The same bias is evident in the judicial system: blacks are arrested and convicted at a higher rate than whites; all other things being equal, a black man found guilty of murder is four times more likely to be sentenced to death than a white man.

The fact that America has a black president throws the Martin affair into even sharper relief. It is tempting to think of Barack Obama as a post-racial figure, but he cannot be. On Friday his first public comments on the case were extremely carefully weighed – as well they might be.

Back in July 2009 (in another case of a black man in a well-off white neighbourhood), the Harvard professor Henry Louis Gates was arrested at his home in Cambridge, Massachusetts. Questioned by a reporter, Obama said the police had acted "stupidly" in arresting his friend. The uproar was mollified only when the professor and the apprehending officer were invited to share a beer at the White House with Obama and Vice-President Joe Biden.

This time the President was scrupulously impartial, calling the case a tragedy, and urging a full investigation. But he said, expressing how he felt for the young man's parents: "If I had a son he'd look like Trayvon." His words were no more than self-evident truth. But they were stunning nonetheless. Will they also help lay to rest America's ancient demon of race? That may be too much to hope for.

Timeline

26 February Unarmed black teenager Trayvon Martin shot dead near home of father's fiancée by Neighbourhood Watch captain George Zimmerman, 28. Zimmerman tells police he killed Martin in self-defence and is not arrested.

9 March Martin's family demands police release 911 tapes or make an arrest.

12 March Media questions police conduct in the case, including alleged "correction" of at least one eyewitness account. Sanford police chief Bill Lee said no evidence to dispute Zimmerman's self-defence assertion.

16 March Excerpts of 911 calls released. In them, Zimmerman says: "This guy looks like he's up to no good, or he's on drugs or something."

19 March US Justice Department announces investigation, and reveals Zimmerman broke Neighbourhood Watch rules by carrying a weapon.

20 March Sanford police admit investigators missed possible racist remark by the shooter before killing.

21 March Sanford city commissioners pass vote of "no confidence" against police chief Bill Lee. Martin's parents join hundreds in New York for "Million Hoodie March". Online petition now has 900,000 signatures and becomes fastest growing online petition ever.

22 March Bill Lee and state attorney Norman Wolfinger agree to withdraw amid accusations of bungled investigation. Thousands rally in Sanford to demand Zimmerman's arrest.

23 March Some 50 schools in Florida stage walkouts. Online petition has 1.5 million signatures. President Obama urges full investigation.