Paul and Margaret Cooke were tapping on the computers in the basement of their Fairfax County home two years ago when their 19-year-old son shot them to death. Tiffany Cooke, away at college at the time, was chatting on the phone with her father and heard her parents being killed.

Her brother, Joshua Cooke, 19, then called 911 and said, "I just shot my parents. I just blew them away with a shotgun, 12-gauge Super Magnum." He calmly waited for officers to arrive.

Joshua Cooke pleaded guilty in the slayings of Paul Cooke, 51, a financial manager at Lockheed Martin, and Margaret Cooke, 56, a retired IBM executive, and was sentenced to 40 years in prison. Now, a long-simmering dispute over their million-dollar estate is headed for court next week, pitting their 21-year-old daughter, Tiffany Cooke, against a family friend and grandmother who have hinted that the daughter may have been involved in the murder.

Even before her brother's guilty plea, Tiffany Cooke, then a freshman at Lincoln University in Pennsylvania, had hired lawyers to stake her claim to her parents' estate, which included not only their home in Oakton on Adel Road but hundreds of thousands of dollars in savings and retirement accounts.

Except for one problem: The Cookes' wills specifically excluded their children from inheriting anything.

The Cookes both graduated from the University of Pennsylvania's Wharton business school and managed their money closely, according to court documents. In 1985, they wrote separate wills. They visited a close friend in Texas, Sharon Spratley, and asked her to be the executor of their estate, if they should both die. Spratley wrote in a court filing that she was "humbled and honored" to be asked.

In each will, Paul and Margaret Cooke agreed to leave half of their estate to Paul Cooke's three sisters, and half to be divided between Margaret Cooke's mother, Ethel Jones, and Spratley.

And in each will, Paul and Margaret Cooke named these adult beneficiaries "to the express exclusion of any child of mine now living or hereafter born."

Several years later, in 1989, the couple adopted Joshua and Tiffany, then ages 6 and 5, from foster care in Ohio. But the Cookes never changed their wills.

Less than three months after the slayings, Tiffany Cooke's lawyers filed a request in Fairfax County Circuit Court that she be declared the executor and her adoptive parents' sole heir because her brother would be ineligible as their presumed killer.

Lawyers for Jones and Spratley quickly came forward with copies of the Cookes' individual wills, naming them as the partial heirs. Still, Tiffany Cooke's lawyer, Wilfred R. Mundle, argued that the wills were written before the children were adopted and therefore were invalid. He wanted the then-teenager named the executor of the estate and the sole heir.

Virginia law states that if a person writes a will before his child is born, "wherein any child he might have is not provided for or mentioned," then the child is entitled to the inheritance.

At a hearing in May 2003, Fairfax Circuit Court Judge Stanley P. Klein said he had read a little about the murders and raised a hypothetical question: "What if the brother were simply covering for the sister?" he asked, about an imaginary case in which a son killed his parents. Shouldn't the people named in the will "have an opportunity to conduct some discovery or to put on whatever evidence they want to put on to establish that the daughter might not be entitled to recover" any money?

Klein named Spratley and Manassas lawyer Thomas O. Murphy, who helped draft the wills, as the executors of the estate. Tiffany Cooke's lawyers appealed that to the state Supreme Court and lost.

Now a trial will be held Aug. 15 to determine the meaning of the will: Did the Cookes really intend to exclude their two children from inheriting the proceeds of their house, which was sold last year for nearly $500,000 more than the Cookes paid in 1987, their apartment in Arlington, their cars and their savings and retirement funds, estimated in court records at more than $600,000?

Spratley argued in legal briefs that they did just that. "The exclusion was intentional, not an oversight," wrote Spratley's lawyer, John F. Boland. He wrote that the Cookes knew in 1985 that they might adopt children later, and the language of the wills was meant "to state firmly that they intended to preclude any adoptee from taking under any circumstances unless the Cookes made later changes to their wills."

Spratley said last week: "I was a very good friend of Margaret and Paul. Margaret and Paul confided in me in good faith. I feel like I need to honor their memory."

Spratley's lawyers also raised the possibility that Tiffany Cooke wasn't entirely innocent in the murders. Noting that she was speaking with her father when he was shot, but didn't call anyone for help, her behavior was "bizarre at best," Boland wrote, "and raises concern to respondent [Spratley] as to Tiffany Cooke's possible involvement with her brother." The brief said that Jones, Tiffany's grandmother, supported further investigation of the circumstances of the death.

Spratley's brief also noted that "the Cookes provided well for their children during their lives and provided considerable life insurance benefits that passed directly to them outside their wills."

Herbert Rosenblum, who is now representing Tiffany Cooke, would not comment. Tiffany Cooke could not be located for comment.

Ethel Jones died in July 2004 and is being represented by one of her beneficiaries, Karen Bond-Louden. Her lawyer, Timothy McEvoy, also would not comment.

The Fairfax court allowed the lawyers to take Tiffany Cooke's deposition, and then Joshua Cooke was interviewed in May by video hookup from Wallens Ridge State Prison. None of the lawyers involved would discuss the results of those interviews, pending the trial Aug. 15.