'Conflicts of interest'
Some legal experts said there could be a conflict of interest for law firms with working ties to GM to be involved in the investigation.
"To me, there's a conflict of interest," said Monroe Freedman, a legal ethics expert and law professor at Hofstra University School of Law. "A reasonable person might question whether the firm wants to curry favor with GM, so it can maintain a good relationship or obtain future work."
GM spokesman Selim Bingol said there is no conflict of interest, and Valukas "has been charged to go where the facts take him and give the company an unvarnished report on what happened. He is the ideal person to do that, given his understanding of our business and his reputation for adhering to the highest standards."
Jenner and King may indeed speed things along, said Stephen Gillers, a professor at New York University School of Law. "It makes sense as a matter of efficiency since the firms know the client," he told Reuters.
In a letter to employees last week, Barra promised an "unvarnished" look at the recall that is occurring 10 years after the issue first came to light. She has not granted any interviews on the matter.
(Read more: NHTSA to GM: Have you been hiding something?)
GM is recalling cars to correct a condition that could allow the engine and other components, including front airbags, to turn off while the vehicle is traveling at high speed. More than 1.6 million older vehicles are affected.
The failure is believed to be caused when weight on the ignition key, road conditions or some other jarring event causes the ignition switch to move out of the "run" position, turning off the engine and most of the car's electrical components mid-drive, with sometimes catastrophic results. GM has recommended that owners use only the ignition key with nothing else on the key ring.
The House Energy and Commerce Committee said it is investigating GM and the National Highway Traffic and Safety Administration's (NHTSA) response to consumer complaints related to the problems with ignition switches.
The committee, led by Michigan Republican Fred Upton, will hold hearings in the coming weeks. Upton led the 2000 investigation into Firestone tire failures on Ford Motor Co vehicles - resulting in the TREAD Act that requires automakers to report complaints of defects to the NHTSA.
"Did the company or regulators miss something that could have flagged these problems sooner? If the answer is yes, we must learn how and why this happened, and then determine whether this system of reporting and analyzing complaints that Congress created to save lives is being implemented and working as the law intended," Upton said in a statement from the committee late Monday.
In an email, GM spokesman Greg Martin said the company was "fully cooperating with NHTSA and will do so with the Committee, too."
Controlling the information flow
GM may be focused on controlling the flow of information from the review.
"If they want to send a message to shareholders that they have uncovered everything, they might hire an independent firm," Richard Painter, a professor at University of Minnesota Law School, told Reuters. "But they may want to disclose just enough to keep shareholders informed, and keep other things private to keep legal defenses available to them."
Sources previously said GM's team of investigators had begun interviewing employees involved in the problems surrounding the ignition switch, which first came to the company's attention in 2004.
GM went through a U.S. government-led bankruptcy in 2009, which is the dividing line between what became known as "old GM" and "new GM."
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Valukas served as lead counsel for the U.S. Securities and Exchange Commission's four-year investigation of "old" GM's pension accounting, which concluded with no allegations of fraud or intentional misconduct.