Jury selection is underway at the start of a trial in Los Angeles of four policemen charged in connection with one of the worst scandals to affect the force for many years.

The men, who were all members of a now disbanded anti-gang unit in the city face conspiracy charges.

Between them, they are alleged to have falsely arrested four gang members, planted evidence on them and then lied under oath to ensure their conviction.

Convictions overturned

The charges against them stem from allegations made by a former member of the anti-drug unit, Rafael Perez, who was caught trying to steal nearly $1m worth of cocaine from a police evidence locker.

In return for a lesser sentence, Mr Perez identified dozens of fellow officers who he claimed had abused their power by beating, robbing and even shooting innocent people.

Perez's former partner in the Los Angeles police department, Nelo Durdan, is currently awaiting trial. He has been charged with attempted murder and armed robbery.

The prosecution claims he and Perez gunned down a 22-year-old youth, planted a gun on him and then lied in court to get him convicted.

Twenty other officers have left the force since the scandal broke and nearly 100 criminal cases have either been dropped or the convictions overturned because they were based on the evidence of policemen whose credibility is now under question.

The Los Angeles Police Department has never fully recovered from the so-called Rodney King affair, when the vicious beating of a black man by four white officers was captured on video tape.