A total of 147 law enforcement officers died in the line of duty in the United States in 1987, down slightly from 159 the year before, the National Assn. of Chiefs of Police said in Miami. Gerald Arenberg, the group's executive director, said: "In 1983 we lost 66 officers, in 1984 the loss was 84 and in 1985 we (lost) 120." Last year's figure could rise, he said, because of "late reports or deaths from injuries where officers are now wounded." Among the 147 deaths, Arenberg said 74 officers were killed in shootings and 57 in traffic-related accidents. California had the most deaths of any state, with 15.