The chairman of the House Judiciary Committee demanded that former Attorney General John Ashcroft testify about his appointment to oversee a Justice Department corporate settlement. The chairman, Representative John Conyers Jr., a Michigan Democrat, said Mr. Ashcroft had not returned calls inviting him to appear on Feb. 26 before a subcommittee that is reviewing the hiring of former government officials as so-called corporate monitors. Mr. Ashcroft, who runs a consulting firm in Washington, is supervising a settlement between the government and Zimmer Holdings Inc., the world's biggest maker of artificial hips and knees. For 18 months work, the company says it will pay him $28 million to $52 million. "Mr. Ashcroft's experience lends a valuable perspective to the hearing as his firm was the recipient of a no-bid monitoring contract," Mr. Conyers said.