District police announced yesterday that reported crime in some categories, including burglary, robbery and arson, declined by an average of 7 percent in 1985 compared with the previous year.

In releasing the figures, Police Chief Maurice T. Turner Jr. credited citizen participation in crime prevention efforts with helping to reduce crime. He said District residents "are crying that they are sick and tired of being victims, and we are giving them help on preventing crimes in their neighborhoods."

The method of crime reporting used by the District is based on a uniform system established by the FBI and reflects "Part I" offenses such as homicides, rapes and aggravated assaults. However, it does not include drug offenses -- a major problem in the District -- or gambling and prostitution.

According to the recent statistics, total crimes against individuals, including homicides, rapes and robberies, decreased from 10,725 reported incidents in 1984 to 10,172 last year. The number of robberies fell from 6,087 in 1984 to 5,230 last year, while reported rapes declined from 298 to 275.

In the category of crimes against property, larcenies from cars declined from 13,156 in 1984 to 11,666 last year and arsons decreased from 333 to 294.

Officials said homicides showed the most marked decline, with 148 last year, the lowest rate in 30 years, compared with 175 in 1984. This year, however, there has been a dramatic increase in homicide, with 28 cases so far this year compared with 15 for the same period last year.

The two categories in which increases were reported were aggravated assault, which increased from 4,097 in 1984 to 4,457 last year and car theft, which rose from 4,374 in 1984 to 5,024 last year.