Robbins Geller Rudman & Dowd has so far avoided sanctions for its controversial use of confidential witness testimony in securities fraud complaints. But its fortunes could soon change.

On Monday the firm submitted a written argument to U.S. District Judge Ruben Castillo in Chicago, who is weighing whether to sanction Robbins Geller for bringing an unsuccessful securities fraud complaint against the Boeing Company based on allegedly false testimony from an anonymous witness. The firm maintains that it acted reasonably.