The black inner city ghettos of the US exploded in the 1960s, in a series of uprisings against racism.
Perhaps the most dramatic wave followed the killing of Martin Luther King, where respect for him clashed with an angry rejection of his call for non-violence.
This rage was behind the founding of the revolutionary Black Panther Party, whose first activity was “patrolling the pigs”.
They followed the police around carrying guns and law books of their own to observe how black people were treated by patrolling officers.
This was in part to stop the appalling toll of young black men who were shot down for “resisting arrest”.
California law was changed to try and stop them carrying guns.
But the radicalism following the civil rights movement shone a light on the murky racism that has always dominated the US legal system and law enforcement.
Indeed the death penalty was effectively halted in the US for a decade from 1967, largely because it was proved to be so racist. Of all those who were executed, 54 percent were black.
This was totally out of step with the proportion of black people in US society. It was also out of proportion with the percentage of crimes said to be committed by black people.
A decade later state executions started again as the right won an argument that each case should be looked at individually without considering wider statistics.
But looking at each case individually hides the institutional racism in the system.
To this day 35 percent of those executed in US jails are black—and another 9 percent come from other racial minorities.
The right’s argument is that this is because these people commit more crime. That’s the same reason they say there are more black people in prison than in university.
But the argument is wrong and needs challenging at every level. It is down to racism.
The Trayvon Martin case throws the way different people are treated into sharp relief.
If Trayvon was white and his killer George Zimmerman was black few people believe he would have been found innocent.
We are rightly outraged at the blatant racism of the US system, but Britain is hardly free of such bias. Only two years ago anger at the shooting of Mark Duggan sparked riots across Britain.
Mark, like Trayvon, was smeared in the media.
The official inquiry into Mark’s death begins in September and we can only hope it brings long awaited justice to his family.
But the inquiry into the police shooting of Azelle Rodney and the inquest into the death of Jimmy Mubenga at the hands of G4S guards exposed the realities of institutional racism that still exists in Britain.