A Montgomery County judge ruled yesterday that Potomac socialite Betty Brown Casey did not coerce her husband, land developer Eugene B. Casey, to put her in control of his $200 million estate and leave his grandchildren with nothing.

In a 176-page opinion, Circuit Court Judge Paul A. McGuckian ruled that Casey did not manipulate her husband into modifying his will before he died in 1986 at age 82.

Eugene Casey, an agricultural policy adviser to President Franklin D. Roosevelt, was one of the richest landowners and businessmen in Montgomery County when he died.

The judge described the lawsuit as "a tangled tale" of a family torn apart by money. Attorneys representing 10 of Eugene Casey's 11 grandchildren argued during a six-week trial last winter that Casey was senile when he revised the will. The lawyers claimed Betty Brown Casey, Eugene's third wife, persuaded him to reduce the inheritance of his children and disinherit his grandchildren.

William F. Gately, an attorney for the grandchildren, said that his clients were disappointed and that they would decide within 10 days whether to pursue their claims.

Betty Brown Casey could not be reached for comment, but her attorney, Brendan V. Sullivan Jr., called the ruling "a complete vindication."

Sullivan said Eugene Casey "had a strong view of the way he wanted to treat his children. She gave them far more money over the years than he did."

Instead of leaving half of his fortune to his children as he planned in an earlier will, Eugene Casey decided in 1985 to leave the money to a charitable foundation headed by his wife and give his children $1 million each. Betty Brown Casey, 67, controls the foundation.

In March 1990, the widow was the apparent target of someone who placed a 12-inch pipe bomb in the trunk of her Mercedes-Benz. As she was being driven from a Northwest Washington clothing store, the bomb blew the back end off the car but caused her only minor injuries.

The crime remains unsolved, and investigators complained that she and other family members were uncooperative.

The judge said Betty Brown Casey appeared more concerned than her husband about the futures of his children and grandchildren.

Noting Eugene Casey's crusty and often selfish ways, his frugality and his willfulness, McGuckian said he believed Eugene Casey knew what he was doing when he revised his will.

After hearing from 15 medical witnesses, McGuckian said he found that Casey suffered from "no substantial mental deficit during 1984 and 1985." The judge described Casey as "a man who while physically enfeebled still maintained total control over his office and his business affairs."

"Eugene B. Casey once characterized himself as a lone wolf," McGuckian wrote. "In any wolf pack, Mr. Casey would have been the alpha male. He was referred to by witnesses from both sides as 'not dominatable,' 'totally individual' and 'always being in control of any situation.' "

McGuckian said it also was clear that Eugene Casey directed his wife's life, not the other way around.

"She testified that Mr. Casey was an old-fashioned man," McGuckian wrote. "He was the boss. He ate when and what he wanted. She recounted his statement that in his marriage, he made 95 percent of the decisions and Betty made 5 percent -- but he told her which 5 percent."

McGuckian said he found it significant that none of Casey's children protested or voiced concerns about his mental capacity when they received notice that the will had been changed in August 1985. The will was revised under the supervision of Casey's attorney, Clark M. Clifford.