Clinton has faced a firestorm of criticism over the pardon from Republicans and Democrats alike.
Mr. Rich stood accused of evading more than $48 million in federal income taxes, making the case against him the biggest tax fraud case in American history.
If convicted, he would have faced a maximum sentence of more than 300 years in jail. Prior to the indictments, he fled to Switzerland, and for 17 years the U.S. government had been unable to get permission from the Swiss government to extradite him.
Clinton last week asserted that he pardoned Marc Rich on the legal merits of his appeal and denied the decision had any connection to campaign contributions or gifts Denise Rich may have given him.
Clinton told reporters "there was absolutely nothing political" about the decision.
Ms. Rich, a singer/songwriter living in New York City, has been a longtime contributor to the Democratic Party and to the Clintons.
Over the past 10 years she has donated more than $1 million to support Democratic candidates, including both Clinton and his wife, Hillary Rodham Clinton, in her successful run for the New York Senate last year.
Most recently, Ms. Rich donated $25,000 for Vice President Al Gore's post-election recount committee. And she gave the Clintons a $7,000 table and chair set they took with them upon leaving the White House. The Clintons have since bowed to critics and pledged to refund the cost of the furniture.
In November, she threw a star-studded charity dinner in New York, raising funds for leukemia research in memory of her daughter, who died of the disease. Ms. Rich's date for the event was Michael Jackson, but all attention was on President Clinton, to whom she gave a special saxophone as a present.
The Clintons' relationship with Denise Rich appears to go back well before that. They reportedly also were at her house the Monday after the infamous Starr Report, describing the president's affair with a White House intern and alleged efforts to cover it up, was released in fall 1998.
Pressed for Pardon Despite Divorce
Though the Riches endured a bitter divorce in 1996 and Marc Rich has since remarried, Denise had been a major advocate in the quiet but aggressive push to convince Clinton to grant the pardon before he left office.
In a Dec. 6 letter to Clinton, Ms. Rich urged the president to grant the pardon, "writing as a friend and admirer …"
Clearly suspicious about Ms. Rich's motivations, the House committee, in one of its 14 questions, asked her whether Mr. Rich or his associates had ever suggested that she or her children would benefit financially as a consequence of her support for Marc Rich's pardon.
Rich, in her letter to Clinton, wrote, "The pain and suffering caused by that unjust indictment battered more than my husband — it struck his daughters and me. We have lived with it for so many years."
A stack of e-mail submitted during the hearing revealed that Ms. Rich wrote the letter with assistance from Marc Rich's lawyers.