General Motors knew about a defect in its ignition switches eight years ago and changed the design of an internal part, but never told federal regulators or the drivers of its cars, according to evidence from a recent lawsuit filed by the parents of a Georgia woman who died in a 2010 GM car crash.
In February the automaker recalled 1.6 million vehicles, saying their ignition switches could be accidentally turned from "run" to the "accessory" position while the car is being driven, shutting down the car's power brakes, power steering and airbags. GM's own figures have linked ignition problems to a dozen deaths.
But evidence from a lawsuit filed by the parents of Brooke Melton, whose Chevy Cobalt spun out of control after shutting off on her 29th birthday, shows that in 2006 GM altered two internal pieces of its ignition switches in a way that would make it less likely for the ignition to shut off accidentally - and made the change without alerting the government or the owners of the cars affected.
"I'm still in shock and boiling over with anger," said Ken Melton, Brooke's father. "Anger that they would sweep something like this under the rug."
Clarence Ditlow, executive director of the Center for Auto Safety, a watchdog group, accused GM of a "callous disregard for human life."
"GM had an obligation under the Safety Act," said Ditlow, "to notify the National Highway Traffic Safety Administration that there was a defect, we're correcting it, and they had the additional obligation to recall the earlier models with the unsafe part."
Four days before the accident, according to the Meltons, Brooke's car had shut off while she was driving and she had lost her power steering and her brakes. She was able to pull her car over and restart it. She called her father, and he said they should take it to a dealership in the morning.
Brooke got her car back from the dealership on March 9, 2010. She died in an accident the next day. "There was no doubt in my mind that it was caused by the same engine cutting off," said Ken. The Meltons called a lawyer.
According to the Meltons, experts contacted by attorney Lance Cooper examined the "black box" from the accident and found that the key had slipped from the "on" to the "accessory" position three seconds before the accident, shutting off her power steering and power brakes. Brooke's car had then hydroplaned on the wet highway and been struck by another car.
Last month, GM recalled the model that Brooke bought, along with other Chevrolets, Pontiacs and Saturns from model years 2003 to 2007. The car company now says the cars are prone to shutting off when the ignition is jostled.
During depositions for their suit last summer, however, the Meltons learned from GM engineers that the company had been aware of potential problems with its ignition systems before Brooke purchased her car in 2005.
Engineers were aware that if the key was jostled or stressed by a dangling keychain it might slip and turn the car off. They proposed that GM keys be altered to make the opening for the key ring smaller.
Instead of changing the keys, however, GM designed an insert that could be added to the keys. It then sent a bulletin to dealerships that said the insert could be provided to car owners who complained about ignition shut-offs.
The Meltons also learned that the car company had made another significant change with even less fanfare.
The detent plunger and spring are two metal parts that fit together inside a car's ignition column. When a car key has been turned to the "on" position, they hold the key in place.
When an engineer working for the Meltons' attorney began buying ignition columns from Cobalts, he found that between 2006 and 2007, GM had made both the detent plunger and its attached spring bigger.
The combined difference in size was only about 1.6 millimeters, or less than the width of a quarter, but the engineer, Mark Hood of McSwain Engineering, told NBC News that the change meant the plunger and spring would exert more force and make the key harder to move accidentally. "The longer plunger and the longer spring is more likely to stay in the run position," said Hood.
Hood also discovered that GM had apparently made the change to the plunger and switch without changing the part number.
"If there is an internal change in the design or construction of the switches I would have at least believed there would be a change in [the] number," said Hood.
During depositions in the Melton case in 2013, a GM design engineer responsible for the Cobalt ignition switch said he didn't recall ever authorizing such a change.
"So if such a change was made, it was made without your knowledge and authorization?" asked the Meltons' attorney.
"That is correct," answered the engineer.
The engineer couldn't be reached for comment by NBC News, and a second engineer who headed up GM's later internal investigation of the ignition switch declined to comment.
The Meltons have now settled with GM for an undisclosed sum. (Their suit against a local dealership is ongoing.) And just weeks ago, in a chronology that it submitted to federal regulators, GM provided confirmation of what the Meltons' attorney's engineer had learned while investigating their daughter's fatal crash.
GM has now disclosed to the National Highway Traffic Safety Administration that a design engineer responsible for the Cobalt's ignition switch "signed a document approving changes to the ignition switches proposed by the supplier, Delphi Mechatronics."
"The approved changes included, among other things, the use of a new detent plunger and spring that increased torque force in the ignition switch," said the document. "This change to the ignition switch was not reflected in a corresponding change in the part number for the ignition switch. GM believes that the supplier began providing the re-designed ignition switch to GM at some point during the 2007 model year."
NHTSA wants to know why the agency wasn't notified of the changes, and has formally demanded to know the names of everyone who was aware of the changes as well as their roles, and why the changes were approved in the first place.
The new CEO of GM, Mary Barra, declined an interview with NBC News, but released a video statement Monday.
"Something went wrong with our process in this instance and terrible things happened," said Barra. "As a member of the GM family and as a mom with a family of my own, this hits home for me."
During a conference call with reporters Tuesday, Barra said the company was conducting a "comprehensive internal investigation."
Barra also apologized "for the loss of life that has occurred." Said Barra, "We will take very step that we can to make sure this does not happen again."
Ken and Beth Melton point out that their daughter Brooke's death is not included in the 12 deaths that GM has attributed to ignition problems. Ken Melton says he's also angry that GM waited until 2014 to disseminate information that was available "so long ago."
"Our daughter might still be here today," said Melton.