Milestones

DIVORCED. Malcolm Forbes, 66, ebullient balloonist, motorcyclist, art collector and millionaire chairman and editor in chief of Forbes magazine; and Roberta Laidlaw Forbes, 61; after 39 years of marriage, five children; in Jackson, Wyo.

ARRESTED. David Crosby, 44, strung-out singer-guitarist with the pop group Crosby, Stills and Nash; on drug, weapon and hit-and-run charges, after he allegedly crashed his car into a fence, fled the scene and was later found to have a .45-cal. pistol and cocaine paraphernalia in the vehicle; in Mill Valley, Calif. It was his third arrest on drug-related charges in the past year.

HOSPITALIZED. Franc,oise Sagan, 50, French novelist and playwright whose shocking first novel about youthful nihilism and passionless hedonism, Bonjour Tristesse (1954), published when she was 18, became an international best seller; in Paris. While on a visit to 8,500-ft.-high Bogota, Colombia, she collapsed with pulmonary edema and cardiac weakness brought on by the altitude; she was flown home to France and remains under sedation in improving condition.

DIED. Dan White, 39, former San Francisco supervisor who in 1978 shot to death the city's mayor, George Moscone, and its first openly homosexual supervisor, Harvey Milk; by his own hand (carbon-monoxide poisoning); in San Francisco. At his 1979 trial, White pleaded "diminished capacity," contending that a diet of sugary junk food had aggravated his severe psychological problems, an argument that became known as the "Twinkie defense." When White was convicted only of voluntary manslaughter, 5,000 rioters, most of them gays, stormed city hall. Following his release after five years in prison, White, unemployed and dogged by fears of retaliation, lived undercover, apart from his family.

DIED. Jean Riboud, 65, French head for 20 years of Schlumberger Ltd., the huge (1984 revenues: $6.4 billion) international petroleum-services company, which he expanded from a narrow base in oil-well testing into a conglomerate with holdings in electronic instruments, semiconductors and computer-aided design systems, and forged into what was widely regarded as one of the world's best-managed firms; of cancer; in Paris.

DIED. Morton Downey, 83, singer known as the "Irish thrush" (though he was U.S.-born) for his high, silvery tenor, who was one of radio's most popular and best-paid stars in the 1930s and '40s on The Camel Quarter Hour and The Coke Club, and later became a wealthy businessman who hobnobbed with socialites and top Democrats, notably the Kennedys; in Palm Beach, Fla.