Serious crime in Montgomery County declined in 1976, down 6.8 per cent from 1975, according to the latest figures released by Montgomery police.

The decline seems part of a trend in the metropolitan area during the past few years, caused at least partially, police said, by emphasis on crime prevention measures and citizen interest in preventing crime.

"People seem to be taking more of an interest in their own things and their neighbors' things," said Cpl. Phillip Caswell, spokesman for the Montgomery police. He added that the number of calls from anonymous citizens reporting suspicious incidents in their neighborhoods has increased greatly in the past few years.

"Before, there might have been four or five burglaries in Chevy Chase, and nobody knew about it," said Caswell. "Now they do. This concern about their community has helped us apprehend criminals."

Prince George's crime statistics for last year will not be available for several weeks, according to a county police official.

Montgomery County's declining crime rate was reflected in the number of crimes reported in the FBI's seven major crimes index for January through December of last year. The total number of major crimes reported in 1976 was 23,052, down 1,684 from 1975 or a decrease of 6.8 per cent.

Figures for categories of major crime decreased in 1976, except murder and rape. There were 26 murders in the county in 1976, six more than the previous year. That is an increase of 30 per cent.

Included in that figure was the mass slaying of the family of Bradford Bishop Jr., a State Department foreign service officer. Bishop's wife, mother and three sons were found murdered in their Carderock Springs home in March. Bishop, the police's only suspect, is still at large.

Also included in that figure are the deaths of two Montgomery policemen, Capt. James E. Daly and Cpl. John M. Frontczak, who were shot trying to apprehend a suspect in the holdup of a Potomac savings and loan association. Robert Daly Angell was later convicted for the murders.

Caswell said that police efforts have little impact on preventing murder. "Murder is very difficult to control. The people usually know each other. It could be a family dispute; it's usually not premeditated. I don't know how we can prevent that."

The number of rapes reported in 1976 was 85, one more than 1975 for an increase of 1.2 per cent. Caswell said that the police department has been sending female officers to instruct women in the county about self-defense and the prevention of rape and also distributing pamphlets on rape. "I think this has helped some," Caswell said.

The number of auto thefts for last year showed the largest decrease in the seven categories - down 18 per cent. There were 1,566 auto thefts reported in 1976, 344 less than 1975. Caswell said that auto theft has been on the decline since 1972 when car manufacturers began installing ignition locks on new cars.

The number of robberies was also down 2.4 per cent, which Caswell said may be partially explained by the creation of a Crime Against the Elderly Unit in Silver Spring. "A lot of elderly people over there had been getting knocked down," Caswell said. "The police unit tells them how to protect themselves, what to look for, what kind of handbags to carry and where not to go."

The number of reported burglaries in 1976 also decreased - to 5,349. This is 200 less than the 1975 figure, a drop of 3.6 per cent. Police have concentrated on prevention. By appointment a police officer will visit a county residence or business, suggest types of locks which might be more effective and engrave the owner's license permit number on his belongings. Response to such police measures have been good, Caswell said.

"I think people are concerned about crime," Caswell said, "but I don't think the fears are as great as they were in the '60s and early '70s. There are not as many radicals tearing around - that always makes people a little jumpy. But they are concerned about their communities."