“By hiring an outfit the government views as credible, thorough, and capable, directors make it more likely that the government will trust the firm’s investigation and forgo its own, which would be more disruptive.” The perspective of this quote, predictably as it comes from Corp. Bd. Mbr., Vol. 11, July/Aug. 2008 at 63, makes it sound like the Board of Directors retains the investigatory law firm (See my posts of 25, 2005; Sept. 27, 2005 #3; Oct. 30, 2005 #2; Feb. 18, 2006 #2; Feb. 19, 2006 #2; and Nov. 24, 2005 #3: independent counsel retained by Boards of Directors.). Bear in mind also that the quote comes from a partner at an AMLAW 20 law firm.
Anyway, in another manifestation of the benefits of cachet, firms that are well known and usually large (and certainly expensive) appear more credible to government agencies, who in effect deputize them to conduct investigations.