Consider what might - and might not - have happened if the jury in a Los Angeles federal court had not convicted two of the officers in the Rodney King case and, like the state panel that triggered last year's riots, acquitted all four again. A full acquittal would have signalled that the American public was prepared to go to almost any lengths to keep crime at bay, even if it meant endorsing brutal behaviour by the police. Public faith in the judiciary, especially among ethnic minorities, would have shrivelled further and racial divisions would have been immeasurably deepened.
Despite hysterical predictions to the contrary, Los Angeles would probably not have rioted. Last year's unrest was ignited by the shock of verdicts that seemed patently ridiculous to everyone (except an almost all- white jury in an out-of-town suburb) who had seen the video-taped beating of Rodney King. This time there was no element of surprise; there were also thousands of police on the streets and troops standing by.
The city has also seen some critical changes in the past year. Although still blighted by many of the causes of the riots - a bankrupt administration, iner-city deprivation, an education crisis, gangs and inter-racial conflicts that sometimes seem to take on all the vicious pointlessness of Northern Ireland or Bosnia - there are new faces and attitudes.
Daryl Gates, the city's pugnacious and unpopular former chief of police, has been forced out of office, to be replaced by the city's first black chief, Willie Williams. And Williams so far is playing to rave reviews from almost all quarters of the community. Furthermore, the mayor, Tom Bradley, who has been in power since the Nixon years, is about to retire; he lost touch with the city years ago. In an almost forgotten primary election tomorrow, 24 candidates aspire to fill his shoes.
Reaction so far to the trialverdict has been one of overwhelming relief. The result has generated a gust of optimistic rhetoric about how Los Angeles is rising from the ashes of its troubled past. It has also confirmed positive impressions of President Clinton's young administration.
But the victory celebrations have obscured the abundant evidence that grubby political expediency and compromised principles have dominated the Rodney King affair - now, perhaps, only a little less than when it first broke.
The Los Angeles riots took place in an election year and prompted a struggling George Bush to proceed with a federal trial of the officers involved, even though it was far from clear that the hearing would be fair. Few juries can have been so acutely aware that an unpopular verdict could cause the world around them to once more erupt in flames. What is the prospect for justice when a jury feels this sort of pressure?
The proceedings were also surrounded by a strong suspicion of double jeopardy. In theory, the officers' federal trial was a different case. The original charges related to the use or not of excessive force by the police officers. The second, federal, case rested on whether they intended to violate Mr King's civil rights. The definition of exactly what constituted 'intent' was never made clear, although the judge did rule that no proof of a conspiracy or premeditation was
But in order to decide whether Mr King's civil rights had been violated, the jury also had to decide whether the officers used excessive force - the same judgment that was required from the panel in the first trial. After this weekend's verdicts, a juror gave an anonymous interview that seemed to confirm what many suspected: 'I think the (video) tape basically speaks for itself. I would say that is basically what convicted them.'
But why was the prosecution successful this time after having failed a year ago? One reason is that the US federal authorities, mindful of the potentially dreadful consequences of losing, picked two of their best lawyers to pursue the case. Barry Kowalski and Steven Clymer were in a different league from Terry White, the inexperienced state attorney who brought the first case. They ensured that this time the jury was ethnically mixed; it included an elderly black man from the troubled inner-city region of Watts, which experienced riots in the Sixties, and a black single mother.
Critically, Mr White had chosen not to call Rodney King to testify. This was partly because he had provided wildly contradictory accounts of what happened and to protect him from being savaged by four defence lawyers. Mr King also has a reputation for flying off the handle when under pressure. The dimensions of this tactical blunder must have become painfully clear in the aftermath of the riots, when the whole world wept as Mr King appealed for calm, asking a question that confronts all America: 'Can we all get along?'
The federal prosecution team did not make the same mistake. They made sure that the jurors' expectations were not allowed to become too high - Mr King has become an icon for some in the black community - by emphasising that he was drunk and on parole for robbery on the night of his beating. Even though it was contradictory and vague, his soft-spoken account in the dock blew a hole in the officers' efforts to portray him as a monstrous figure, an out-of-control giant from the ghetto who reared up at them from the ground every time they tried to subdue him. He came across as an average man with a mildly criminal bent, decidedly ordinary flesh and blood. 'I was,' explained Mr King with engaging simplicity, 'just trying to stay alive, sir.'
The prosecution notched up several other unexpected bonus points. When Melanie Singer, a California Highway Patrol officer, was called to the stand by the defence, she was supposed to describe Mr King's bizarre behaviour after he was stopped following a car chase. She most certainly was not expected to burst into tears - not once but twice - as she remembered the beating.
The second significant triumph is certain to be the subject of at least one of the convicted officer's appeals. US District Judge John Davies allowed the prosecution to play a video-tape of testimony given in the first trial by Theodore Briseno, one of the two acquitted officers. In it, Mr Briseno condemned the beating, but he later decided not to give evidence again - so allowing the officers to present a united front. In effect, he became a star witness against his colleagues, yet one who could not be cross-examined by their lawyers.
The defence invested its trust in the performance of Sgt Stacey Koon, who supervised the beating and was the only officer to testify. He also produced an astonishing reminder of what the police can legally do to someone they are 'subduing'. Koon said that he had wanted to 'cripple' Rodney King by ordering his officers to smash his elbow and knee joints, so that he could not get off the ground. Many Americans must have asked themselves the question posed by the prosecution. Is this really the way they want their policemen to behave? Finally - after 72 hours of deliberations by 24 jurors in two courts - America has falteringly concluded that the answer is 'no'.
Reaching this conclusion proved an agonising and perilous process, even for the world's most powerful democracy. The second trial was a gamble because the officers could again have walked free. But the administration will surely feel it was worthwhile.
Its conclusion almost certainly will be that tampering with the right of four individuals not to be tried twice for the same offence was justified in order to curb police excesses and restore a modicum of public confidence in a legal system that had lost the trust of many millions of Americans.