The attorney, Stuart Stein, told a federal appeals court Wednesday that Dummar deserves another shot at the money because of pilot Robert Diero, who came forward in 2004 to say he flew Hughes to a brothel in Nevada around the time and the place that Dummar said he found Hughes.
Stein, an estate-planning lawyer from Albuquerque, N.M., with a radio show, argued that Hughes' associates knew about Diero but didn't disclose it at the original probate trial in 1977-78.
"The judgment was obtained by fraud," Stein told a three-judge panel of the 10th U.S. Circuit Court of Appeals in Denver.
Dummar's lawsuit seeks the money from two men who benefited from Hughes' will, one of whom is deceased. Randy Dryer, an attorney for one of the estates, told the appeals judges that Stein's allegations of fraud are based on "speculation and conjecture."
And Dryer said that even if a jury heard from Diero and believed the story, "It doesn't necessarily follow that the jury would have concluded that the (will) was valid.
"They could have easily concluded that Mr. Dummar saw a golden opportunity to reward himself for his good deeds," Dryer said.
Dryer also argued the will already has been determined to be a forgery, saying that it doesn't contain the authentic writing of Hughes.
Dummar is among the most famous of hundreds of people who came forward claiming to be heirs to Hughes' estate after the eccentric billionaire's death in 1976.
Now 63, Dummar delivers frozen food and lives in Brigham City, Utah. He says as a 22-year-old man he was driving across the Nevada desert in December 1967 when he came across a "bum" near Lida Junction and gave him a ride to the Sands Hotel in Las Vegas.
Dummar said the man claimed he was Hughes, but he didn't believe it until someone he said was Hughes' personal messenger delivered the handwritten will to the Brigham City gas station that Dummar owned.
It included instructions to turn the will over to The Church of Jesus Christ of Latter-day Saints, which also stood to gain $156 million. The church never pursued a claim.
Diero said it wasn't until years later that his memories about the flight were jogged by a newspaper article mentioning Lida Junction, a tiny community about 150 miles north of Las Vegas and six miles from the place where Dummar claims he found Hughes.
Diero had been a director of aviation facilities for Hughes Tool Co. He broke a nondisclosure agreement with the company when he came forward with his account of flying Hughes from Las Vegas to the Cottontail Ranch brothel for a tryst with a diamond-toothed prostitute. After losing track of Hughes, Diero said he returned to Las Vegas without him.
Diero has said he routinely delivered Hughes on secret nighttime flights in a single-engine plane to rural Nevada brothels, a claim disputed by others familiar with Hughes.
After Diero came forward, Stein renewed Dummar's claims in court, seeking money from Hughes' cousin, William Lummis, and the estate of Frank Gay, who was chief operating officer of Summa Corp., which controlled Hughes' major assets.
Lower courts dismissed the claims, so Dummar appealed to the 10th Circuit on the grounds that the alleged fraud meant the case had not been fairly and fully litigated.
Gay died in May 2007 at age 86. Lummis is retired and is living in Texas. Peggy Tomsic, an attorney for Gay's estate, asked the appeals court to uphold the ruling against Dummar in the original probate case.