By David Willis in Los Angeles

The jury in one of America's strangest murder trials is expected to decide on Monday whether two 21-year-old men should go to jail for life for a killing which even the prosecution concedes they did not commit.

The men have been charged under a little-known law called "provocative act" and, if the prosecution can prove that they provoked a brawl in which their friend died, they will effectively be found guilty of his murder.

Gang fight

Two years ago, in the small town of Vacaville, east of San Francisco, two gangs of teenagers got into a fight.

Several of them had weapons and one of the boys - 16-year-old Jeremiah English - was stabbed to death.

His arch-rival, Chad O'Connell, later admitted killing Jeremiah with a hunting knife, but managed to convince prosecutors that he had acted in self-defence.

Chad O'Connell was charged with a minor weapons offence and has since become a prosecution witness in the trial of two other people.

Accused of murder

David Moreno and Justin Pacheco fought alongside Jeremiah English on the night he died and even drove their bleeding friend to hospital.

Yet they now stand accused of murder under a rarely-used law which states that anyone who provokes a confrontation which leads to death can themselves be held responsible for the killing.

Such a law is recognised in just two states - California and Maryland - and the prosecution claims that Mr Moreno and Mr Pacheco were looking for a fight on the night in question and that, as a result of their provocative behaviour, Jeremiah English died.

The case has proved highly controversial not only because it is so unusual.

Race factor

Of the nine people involved in the fight, seven - including Chad O'Connell - were white.

The only two non-whites were Mr Moreno and Mr Pacheco, both of whom are of Hispanic descent.

Hispanic youths are sometimes seen as the ring-leaders in gang-related crime and several human rights groups complain that prosecutors are unjustly using the provocative act law in an attempt to crack down on the gangs.

If the jury finds David Moreno and Justin Pacheco guilty of provocative act murder, they could both go to jail for up to 25 years.