Today, Sen. Elizabeth Warren (D-MA) sent a letter to Attorney General Eric Holder inquiring as to why the Department of Justice failed to prosecute a single major Wall Street bank executive in the wake of the financial meltdown.

“Have you conducted any internal research or analysis on trade-offs to the public between settling an enforcement action without admission of guilt and going forward with litigation as necessary to obtain such admission and, if so, can you provide that analysis to my office?” wrote Warren.

The letter was also addressed to Federal Reserve Chairman Ben Bernanke and Securities and Exchange Commission Chairwoman Mary Jo White.

In a May 2012 Daily Beast article, Government Accountability Institute President Peter Schweizer and veteran journalist Peter Boyer reported that Holder’s DOJ has failed to prosecute a single top Wall Street executive and that DOJ financial-fraud prosecutions are at 20-year lows. 

Furthermore, Schweizer and Boyer revealed that Eric Holder’s former law firm, Covington & Burling, counts among its clients top financial firms and banks, including: Goldman Sachs, JPMorgan Chase, Citigroup, Bank of America, Wells Fargo, and Deutsche Bank. 

Holder also installed other Covington & Burling lawyers in the Department of Justice, as well as others whose past firms represent the big banks:

Lanny Breuer, who had co-chaired the white-collar defense unit at Covington with Holder, was chosen to head the criminal division at Obama’s Justice. Two other Covington lawyers followed Holder into top positions, and Holder’s principal deputy, James Cole, was recruited from Bryan Cave LLP, another white-shoe firm with A-list finance clients.

With Holder now under intense fire for the Associated Press-DOJ snooping scandal, it remains to be seen whether Warren will get the answers she seeks about the DOJ’s refusal to prosecute Wall Street. Given Schweizer and Boyer’s revelations last year, perhaps Warren would do well to revisit the crony connections between Eric Holder, Lanny Breuer, Covington & Burling, and Wall Street.