Gov. Marvin Mandel proposed a new death penalty law today designed to meet the latest guidelines laid down by the U.S. Supreme Court.

Although Maryland has had a death penalty on its law books since 1776, the last execution in the state's gas chamber occurred in 1961. Despite revision, the law has twice been held in recent years to fall short of the evolving Supreme Court standards for imposing the death penalty.

State legislative leaders said they anitcipate long and emotional debates over capital punishment at the current General Assembly session as a result of the governor's proposal and the recent execution in Utah of Gary Gilmore.

Alan Wilner, Mandel's chief legislative aide, who helped draft the new death penalty bill, said, "the governor's feeling is that the General Assembly has always favored capital punishment but he is concerned that if we are going to have a capital punishment bill it should be constitutional, not like the last couple of laws."

Last year the Maryland Court of Appeals struck down the state's capital punishment law because it called for mandatory imposition of the death penalty on conviction for certan crimes of murder. That law was enacted to meet the 1972 Supreme Court ruling that the death penalty as it was then applied, was cruel and unusual punishment because of the opportunities for arbitrariness in state laws most of which gave juries "unbridled discretion" on the life-or-death decision.

Mandel's proposed legislation generally follows the laws of Florida and Georgia that were upheld by the Supreme Court last summer.

The bill would give juries and courts "guided discretion" in imposing the death penalty. The penalty would be imposed only after a two-stage proceeding.

A first trial would determine whether a person is guilty of first-degree murder.

A second trial would be held for someone who had been convicted to determine what the sentence should be - death or life imprisonment. The same judge and jury who heard the first trial or a different judge and jury could hear the second trial.

The new law would expand the number of crimes punishable by death. The law now on the books says death may be imposed for murder of a law enforcement officer, murder while a prisoner at a correctional institution or while trying to escape from such on institution, murder by contract, murder while under sentence of life imprisonment or death, and murder while attempting robbery.

Mandel's bill would add to this list murder while attempting to commit or committing arson, mayhem (mutilation of a person) rape or to other first-degree sexual offense.

If a jury or judge found beyond a reasonable doubt that one or more of the above "aggravating circumstances" accompanied a first-degree murder, the jury or judge would be called on to decide if there were mitigating circumstances, such as whether the defendant was only a minor accomplice or acting under orders or emotionally disturbed, and whether the defendant would be likely to continue criminal activity.