All in the Family

Even as she showered her sons with the proceeds from her $10 million tobacco fortune, Margaret Hitchcock Benson lived in fear of them. There were constant fights and drugs and a nightmarish unhappiness that led her to believe that one or another of them was stealing her funds and wanted her dead.

Her apprehension was well founded. A year ago, as she sat in her station wag- on in the driveway of her home in the wealthy South Florida city of Naples, a powerful pipe bomb exploded between the front seats. Margaret Benson, 63, and her adopted son Scott, 21, were killed immediately. Her daughter Carol Lynn, now 42, was seriously injured but escaped from the car moments before a second bomb blast.

Last week, after deliberating 11 1/2 hours on testimony heard during a four- week trial, a jury in nearby Fort Myers found her son Steven Benson, 35, guilty of two counts of first-degree murder, two of felony murder and five relating to arson and unlawful explosives. Judge Hugh D. Hayes Jr. said he intended to heed the jury's recommendation for life in prison when formal sentencing occurs next month.

Prosecutors presented 52 witnesses who painted Steven as an improvident drifter whose business failures apparently led him to misappropriate some of his mother's fortune. Only days before the explosions, Margaret Benson asked a family lawyer to investigate. Steven, the prosecutor argued, feared disinheritance. Experts testified that his handprints were found on receipts for a length of 4-in.-diameter pipe ($36.08, including tax) and two pipe endpieces ($28.05 total) of the kind used in the fatal bombs. Steven's sister, her face bearing ugly burn scars from the bombing, told the court that he left the car just before the blast, ostensibly to get something from the house, and kept his back to her as she screamed for help.

Steven's lawyers contended that the killings could have been the work of young Scott's enemies, made during a fast-track life of girl chasing and drug buying. Scott, it was disclosed after the murders, was the out-of-wedlock son of Carol Lynn; he had been legally adopted by his grandmother.

Steven, considered mild-mannered around Naples, where the freshly widowed Margaret Benson had moved from Lancaster, Pa., in 1980, wept twice during the trial. When the verdict was pronounced, he sat in choked silence. The defense planned to appeal.