LONDON (AP) _ Judges, not defendants, will decide whether a jury should hear certain cases under a legislative proposal announced by the government today.

Home Secretary Jack Straw, the Cabinet official in charge of criminal justice, said many defendants were using the right to a jury trial to delay the system.

``In 1998, there were 18,500 cases in which the defendant demanded their case be heard before a jury. In many of these the defendant changed their plea to guilty when they appeared in court,'' Straw said in a speech to the Police Federation Conference in Blackpool.

The change will apply to offenses such as theft, burglary, assault and criminal damage, which may now be tried either before a magistrate without a jury, or in a jury trial in Crown Court. More serious offenses will continue to be tried in Crown Court.

Other less-serious cases such as motoring offenses and drunkenness are already tried exclusively before magistrates.

``This manipulation of the system cannot be right,'' Straw said. ``It causes anxiety and concern to victims and witnesses and it costs the taxpayer thousands of pounds in extra court costs and legal aid. It also wastes the valuable time of police officers, prosecutors and judges who prepare for a trial only to be stood down because of the changed plea.''

Defendants will have a right to appeal a magistrate's decision to refuse a jury trial, he said.

The government will introduce the legislation as soon as possible, but Straw did not specify a date. The governing Labor Party has an overwhelming majority in the House of Commons, and the measures are likely to pass.

Courtenay Griffiths of the Society of Black Lawyers said minorities were skeptical of the fairness of Magistrates' Courts.

``A fair hearing from a randomly selected panel of jurors greatly enhances the confidence that minority communities have in the justice system,'' Griffiths said.

About 40 percent of defendants in Crown Court jury trials are freed, compared with 25 percent tried in Magistrates Courts.