Former U.S. Attorney Anton Valukas, who was hired by GM to do the investigation, will also testify. Panel members will question Valukas on his conclusions that a lone engineer, Ray DeGiorgio, was able to approve the use of a switch that didn't meet company specifications, and years later, to order a change to that switch without anyone else at GM being aware, the congressional aide said.
The panel's own investigation turned up evidence that at least five other GM employees were aware that DeGiorgio ordered the company that made the part to change the switch, the aide said.
Barra plans to tell lawmakers that she's taken steps to fix GM in the wake of the small car recall. She authorized a companywide safety review that has led to more than 40 recalls this year that cover almost 18 million cars in the U.S. GM has said that more are possible.
Here are some other questions lawmakers are likely to ask Barra and Valukas:
—Q: How does GM plan to change the cumbersome corporate culture laid bare by Valukas's report?
Valukas' investigation found that a pattern of incompetence and neglect within GM kept the ignition switch problem concealed for 11 years. Rep. Diana DeGette of Colorado, the senior Democrat on the Energy and Commerce investigative subcommittee, said this week she wants to know "what are they going to do to break this culture." Barra has acknowledged that the report drew a "deeply troubling" portrait of GM as an organization. According to her prepared remarks, Barra will tell the hearing that GM has restructured its process for making safety decisions "to raise it to the highest levels of the company," among a number of changes.
—Q: How will GM compensate victims of crashes linked to the faulty switches?
Barra says the company expects to begin processing victims' claims for compensation by Aug. 1. Lawmakers want details. GM has hired attorney Kenneth Feinberg to put a plan in place; he'll rule on who is eligible to receive compensation and will set the amounts. More than 300 claims have been filed. Feinberg has presided over compensation plans for the victims of the Sept. 11 terrorist attacks, the 2010 BP oil spill in the Gulf of Mexico and other disasters.
—Q: Could the seeds of an even wider problem be lurking within GM's corporate structure?
Barra has said that the safety review is nearly complete and hasn't turned up any other serious problems. She called the ignition-switch debacle a "unique series of mistakes" made by the company over many years. The news Monday of another huge recall for a problem similar to the ignition-switch defect has fueled lawmakers' skepticism. "This latest recall raises even more questions about just how pervasive safety problems are at GM," Rep. Fred Upton, R-Mich., chairman of the Energy and Commerce Committee, said.
—Q: How bad were the problems at GM.
He and his team know GM thoroughly after interviewing 230 employees and reviewing 41 million documents. Valukas will tell the hearing that his team found an alarming "lack of urgency" among GM employees to fix the switches, magnified by a dysfunctional corporate structure. He acknowledges that his report leaves open some questions, notably: whether there was civil and criminal culpability; whether GM will make the right decisions to stop this from happening again; and what specific crashes were caused by the ignition switch problem.
—Q: Do the actions that GM has taken so far appear sufficient?
In addition to making organizational changes, the company forced out 15 employees and disciplined five others for their roles in the ignition-switch debacle. More than half the 15 were senior legal and engineering executives who failed to disclose the defect and were part of a "pattern of incompetence," according to Barra. The Justice Department likely will use Valukas' findings as a "road map" for questions and employees to pursue in its criminal investigation.