in the film, apparently in order to preserve the protagonist's personal integrity, mitch exposes a systematic overbilling scheme by the firm, thus driving a wedge between the moroltos (who in essence become complicit with mitch) and their law firm (in the book, overbilling only received a brief mention). he receives a smaller amount of money from the fbi, which he gives to ray, allowing him to disappear. rather than capitalizing on his circumstances by stealing money from the firm, as in the book, the movie's mcdeere ends up battered and bruised, but with his integrity and professional ethics intact. mitch also makes the fbi have to work in order to bring down the firm by having to argue that each instance of excessive billing is a federal offense (by virtue of the excessive bills being sent through the mail). the volume and frequency meets the criteria for rico, thereby enabling the fbi to effectively put the firm out of business by seizing its property and equipment and freezing its bank accounts. from here the moroltos would then need to find another law firm willing to take them on as clients, and if they couldn't, charges for non-lodgment of tax returns could be brought. since mitch is exposing only illegal activity, he is able to retain his law license.