Mr. McKay at his Washington office in 1987. (Charles Tasnadi/AP)

James C. McKay, a Washington trial lawyer who as independent counsel investigated alleged influence-peddling in the Reagan administration in the 1980s, a controversial probe that ended with an ambiguous judgment of then-Attorney General Edwin Meese III, died Nov. 23 at his home in Chevy Chase, Md. He was 98.

The cause was aspiration pneumonia, his son James C. McKay Jr. said.

A specialist in areas including antitrust law, Mr. McKay joined Covington and Burling in the 1940s, rose to partner and practiced with that firm, the largest in Washington, for more than six decades.

He was a principal attorney for the National Football League, one of the firm’s most prominent clients, in antitrust and other matters. In the 1980s, he helped represent Eli Lilly and Co., the pharmaceutical giant, in high-profile litigation arising from deaths that were linked to Oraflex, a drug prescribed for the treatment of arthritis.

His most public role came during his tenure as independent counsel. He was appointed to the position in 1987 after the Justice Department requested a special prosecutor to investigate Lyn C. Nofziger, a longtime Reagan aide who served in the White House as assistant for political affairs and who was accused of conducting illegal lobbying activities after he left the administration in early 1982.

A panel of the U.S. Court of Appeals for the District of Columbia Circuit selected Mr. McKay for the job, describing him as “an outstanding trial lawyer of wide experience,” the New York Times reported at the time, and granted him broad authority to pursue questions that arose in the course of his investigation.

Federal ethics rules restrict the lobbying activities of high-ranking government officials for one year after they leave office. Nofziger was accused of improperly aiding clients including Welbilt Electronic Die Corp. (later renamed Wedtech ), a military contractor in the Bronx that obtained a $32 million no-bid government contract for the manufacture of engines.

Previously pursued by then-U.S. attorney Rudolph W. Giuliani, the Wedtech investigation grew under Mr. McKay to include Meese, who acknowledged intervening for Wedtech during his time as White House counselor.

In 1988, Mr. McKay released an 800-page report finding that “currently available evidence does not show any criminal wrongdoing” by Meese in the Wedtech controversy.

It found that Meese “probably violated the criminal law” by submitting a false income tax return, failing to pay capital gains taxes and participating in regulatory matters involving telecommunications companies in which he held stock. Mr. McKay declined to pursue criminal charges against Meese, according to the report, because there was “no evidence that he acted out of self-interest.”

Meese, who by then had announced his intention to step down as attorney general, said Mr. McKay had conducted a “fishing expedition” that cost $1.7 million and produced “an empty net.” Meese accused the independent counsel of violating “every principle of fairness and decency” by alleging his probable guilt without charging him in court.

Mr. McKay responded that “it all came down really to the question: ‘If this were an ordinary person, would he be prosecuted?’ ”

“We concluded that he probably would not be,” Mr. McKay said. “We felt that we should treat Mr. Meese just as an ordinary citizen should be treated and not simply because he’s the No. 1 individual in the Department of Justice . . . It wasn’t a cheap shot.”

In February 1988, in a prosecution overseen by Mr. McKay, Nofziger was convicted of illegal lobbying. An appeals court overturned the conviction the next year, finding that prosecutors had not demonstrated criminal intent.

Mr. McKay was one of numerous independent counsels, most prominently Lawrence Walsh in the Iran-contra affair, who were tasked with investigating Reagan officials. The office of independent counsel remains a sensitive post, often susceptible to allegations of unfairness.

“It’s become so politicized now,” Mr. McKay told the New York Times in 1998, during Kenneth Starr’s investigation of President Bill Clinton, “that the ins hate it and the outs love it just for the purpose of bringing the ins down. That’s the part that will turn the public sour.”

James Creighton McKay was born in South Pasadena, Calif., on Feb. 24, 1917, and he grew up in Washington, where his father was an Agriculture Department economist.

The younger Mr. McKay graduated from Western High School in 1934, received a bachelor’s degree from Cornell University’s agricultural college in 1938 and worked for a period for the federal agriculture agency.

He served in the Navy during World War II, commanding a patrol craft in the Mediterranean, before receiving a law degree from Georgetown University in 1947.

While at Covington and Burling, he did pro-bono work in adoption, child custody and child abuse cases on behalf of military veterans and for indigent criminal defendants.

He was a trustee of the George Preston Marshall Foundation (formerly the Redskin Foundation) and belonged to the Chevy Chase Club in Maryland and the Metropolitan Club in the District.

Survivors include his wife of 72 years, the former Mary Anne Hunter, of Chevy Chase; three children, James C. McKay Jr. of Washington, Patti McKay of San Rafael, Calif., and Robert H. McKay of Avondale Estates, Ga.; and three grandchildren.

In 2001, Mr. McKay joined the Justice Department for a stint with the Professional Responsibility Advisory Office, becoming “one of the oldest Justice Department lawyers ever hired,” according to The Washington Post. In 2007, when Mr. McKay was 90, Washingtonian magazine wrote that he “may be Washington’s oldest active attorney.”

In addition to his legal practice, he wrote several books, among them a semi-autobiographical novel about his experience in World War II and an 800-page unpublished novel about an independent counsel.