Howard County judges, prosecutors and defense attorneys will be asked to test their endurance and the swiftness of justice next month during three days of marathon court hearings designed to reduce a backlog of misdemeanor cases that threaten to delay other trials.

Under a plan approved last month by Chief Judge Robert F. Fischer, scores of defendants, lawyers and potential jurors will crowd the courthouse corridors and small courtrooms as the county's four circuit judges each hear about 50 misdemeanor cases a day for three days.

Normally, between seven and 30 criminal misdemeanor cases are heard once a week on Fridays.

The criminal misdemeanor cases primarily involve motor vehicle violations, such as drunken driving or driving with suspended or revoked licenses, trespassing, larceny and first-time drug offenses.

Usually these cases are handled in District Court. But because of a 1984 Maryland appeals court decision broadening the rights of defendants to have jury trials in misdemeanor cases, more defendants are requesting them, which means their cases are heard in Circuit Court.

No jury trials are held in District Court.

Because the decision covers all of Maryland, the backlog problem doesn't affect just Howard County. However, Howard decided to solve its problem by having the three-day marathon.

In addition to the appeals court ruling, court officials said the growth in jury trials for misdemeanors stems from a rise in drunk driving cases and more postponements sought by defense attorneys.

Judges also say more defendants charged with minor criminal violations ask for juries to avoid district judges with reputations for imposing stiff or unusual sentences.

"There is no place to put the cases we have," said Dwight Thompson, Howard's deputy state's attorney. "The system is losing ground."

Jury trial requests from the district court now account for almost 50 percent of the criminal caseload in Howard's Circuit Court, Thompson said. Of the 1,118 pending criminal cases at the end of December, 487 were jury trial referrals from District Court, he said.

The number of jury trial requests is climbing statewide, said Peter J. Lally, assistant state court administrator in Annapolis.

In the year ending last July there were 55,247 pending criminal cases in Maryland circuit courts, of which 28,244 were jury trial requests from district courts, Lally said.

In comparison, in 1982, there were 6,000 requests for jury trials, he said.

"We're swamped," said Circuit Judge John J. Mitchell, chief administrative judge in Montgomery County. Mitchell said he assigns six judges to handle an average of 135 jury trial requests that are heard each Wednesday. "Things are tough all over," Mitchell said. "It's definitely no fun."

In Howard, the marathon hearings set for March 14, 15 and 18 are the latest attempt to curb the escalating problem, Thompson said.

Six months ago, the court set aside Fridays to schedule plea bargains and hearings on misdemeanor cases sent up from District Court. But Thompson said the system has failed to clear up the heavy criminal caseload.

If the current plan doesn't work, Fischer said he may have to consider a moratorium on civil trials and give precedence to criminal matters. "That is a possibility," he said.

In Prince George's County, Circuit Court Judge Vincent J. Femia reversed the problem by handling jury trial requests full time, shepherding the cases through the system. Since then, the jury trial requests have dropped from 350 a month to about 200 a month, Femia said.

Last year, there were 3,281 jury trial requests from District Court compared with 4,411 in 1986.