The Secret Service is investigating itself in the Colombia prostitution scandal, rather than turn the probe over to the independent Inspector General who typically looks into allegations of misconduct by Department of Homeland Security officials.
The approach appears to be the result of a special carve-out for the Secret Service forged a decade ago -- setting it apart from the standard described in a 2009 internal DHS memo, which specifically asserts that the Inspector General is "statutorily responsible for conducting and coordinating all investigations" of wrongdoing by other Homeland Security employees.
On Wednesday, Sen. Charles Grassley told ABC News he is not comfortable allowing the Secret Service's own internal affairs division to oversee the investigation -- especially because it remains unclear whether the raucous behavior in Colombia was a one-time lapse, or the sign of a broad systemic problem.
"An investigation by the agency's own Office of Professional Responsibility is necessary, but it doesn't provide transparent, independent oversight without an Inspector General's outside perspective," the Iowa Republican said Wednesday. "There's too much at stake to leave any doubts that an independent investigation wasn't conducted."
Grassley asked Napolitano during her appearance before a Senate committee Wednesday whether the department's independent, investigatory arm, the Office of Inspector General, would step in and undertake its own probe into the matter.
Napolitano responded that there is a standing agreement -- "a memorandum of understanding" -- between the Secret Service and the Inspector General that governs how internal investigations are conducted. "In these types of cases, where there is alleged misconduct, [the Inspector General] actually supervises the investigation but they use the investigatory resources of the Secret Service. That's how we are managing this one."
That is not, however, how the Inspector General's office described the arrangement in response to questions from ABC News Wednesday, in an exchange that occurred after Napolitano gave her answer to the Senate.
Spokeswoman Rachael Norris told ABC News that the inspector general is "closely monitoring" the Secret Service's investigation and will review it when it has been completed.
"We're monitoring their internal investigation at this time," Norris said. "We are not conducting an additional investigation at this time."
The Inspector General's subordinate role appears to date to 2003, when the Secret Service was moved from the Department of Treasury into the newly created Homeland Security department. Both the Secret Service and the Coast Guard, which was moved from the Transportation Department to DHS the same year, retained their internal investigative powers.
White House: No Staff Involved in Scandal
Investigation of misconduct in those two agencies appears to differ from the manner in which the Inspector General handles oversight of other agencies within Homeland Security. In a Dec. 16, 2009 memo, written to U.S. Customs and Border Protection, the Inspector General took issue with efforts by that agency's internal affairs division to investigate misconduct by its own Border Patrol agents.
"The Office of Inspector General is the organizational element within the U.S. Department of Homeland Security that is statutorily responsible for conducting and coordinating all investigations of suspected criminal wrongdoing by DHS employees, and has specific oversight responsibility for internal investigations performed by components," asserted Thomas M. Frost, then the assistant inspector general for investigations, in the memo.
Grassley said he believes the approach should be the same in the case of alleged Secret Service misconduct.
"The Inspector General should take a more active role because we can't be left with any questions that the protection of the President and national security are at risk," he said.
Grassley has also engaged in a war of words with the Obama administration over its handling of his question about the possibility that any White House advance staff joined in the partying in Colombia that occurred in advance of the president's arrival there.
Press Secretary Jay Carney said the White House Counsel's office conducted its own internal review and concluded no White House staff had participated. Grassley has sent the White House a letter asking that the details of its internal review be made public.
The Inspector General's office told ABC News it has not deviated from its standard procedure in this case. And Napolitano told senators she has "full confidence" in the Secret Service's ability to conduct its own internal review.
"Director Sullivan has the President's and my full confidence as this investigation proceeds," she said. "The investigation will be complete and thorough and we will leave no stone unturned."