Dunn Lampton, a former U.S. attorney in Mississippi who prosecuted two civil rights-era cold cases and a complex corruption case involving a wealthy attorney and state judges, has died. He was 60.

Among Lampton's best known cases was the prosecution of James Ford Seale, a reputed Ku Klux Klansman who died in prison this month. Seale was convicted in 2007 of two counts of kidnapping and one of conspiracy to commit kidnapping in the 1964 deaths of Henry Hezekiah Dee and Charles Eddie Moore, both 19.

Lampton died Wednesday evening, according to former acting U.S. Attorney Donald Burkhalter, one of the prosecutors who served after Lampton's 2009 retirement

"He was a hell of a trial lawyer and he did a good job as U.S. attorney," Burkhalter said Thursday. "I think he always tried to do the right thing."

The cause of death was not immediately released, but Lampton had been in declining health. The U.S. attorney's office said the funeral will be at 1 p.m. Saturday at Covenant Presbyterian Church in Jackson. Burial will be private.

President George W. Bush appointed Lampton as U.S. Attorney for the Southern District of Mississippi in September 2001, putting him in charge of federal prosecutions in 45 counties.

Among the highlights of Lampton's career were prosecutions in two civil rights-era cases that led to the convictions of reputed Klansmen Seale and Ernest Avants.

The Justice Department is investigating whether the Standard & Poor's credit ratings agency improperly rated dozens of mortgage securities in the years leading up to the financial crisis, The New York Times reported Wednesday.

The investigation began before Standard & Poor's cut the United States' AAA credit rating this month, but it's likely to add to the political firestorm created by the downgrade, the newspaper said. Some government officials have since questioned the agency's secretive process, its credibility and the competence of its analysts, claiming to have found an error in its debt calculations.

The Times cites two people interviewed by the government and another briefed on such interviews as its sources. According to people with knowledge of the interviews, the Justice Department has been asking about instances in which the company's analysts wanted to award lower ratings on mortgage bonds but may have been overruled by other S&P business managers.

If the government finds enough evidence to support a case, it could undercut S&P's longstanding claim that its analysts act independently from business concerns. The newspaper said it was unclear whether the Justice Department investigation involves the other two major ratings agencies, Moody's and Fitch, or only S&P.