The court-appointed trustee recovering money for Bernard L. Madoff's victims is preparing a wave of new lawsuits seeking to wrest funds away from investors who also were duped by the Ponzi scheme. In an interview, Irving Picard said he could wind up suing about half the estimated 2,000 individual investors he has called "net winners" from their dealings with Mr. Madoff. Such investors withdrew more from Mr. Madoff's firm than the amount of principal they invested. "The people who made money, who got more, have made money at the expense of the people who didn't," said Mr. Picard, who has...