At a meeting on Jan. 31, 2006, G.M. lawyers reviewed the fatal crash of Amber Marie Rose. Ms. Rose, 16, of Dentsville, Md., had been killed the previous July when the 2005 Cobalt she was driving hit a tree. Her air bag did not deploy, and she slammed into the steering wheel so hard that she broke it.

At the meeting, Kathy Anderson, a G.M. engineer, said that the air bag was not expected to deploy, because it was not a head-on collision. Instead, the car’s front right corner made contact with the tree. Moreover, the car had hit several small trees before coming to a rest, which suggested a softer impact. The vehicle’s power mode also had been in “accessory” instead of “run” at the time of the crash, but Ms. Anderson said that was not a focus of her investigation, because she felt that the air bag ought not have deployed in the first place.

Lawyers homed in on the problem more closely in 2007, as they discussed another lawsuit that had been brought against G.M. — that of Candice Anderson, whose 2004 Ion ran off the road in fall 2004 while she was driving, with her boyfriend in the passenger seat. She survived, but her boyfriend was killed. Ms. Anderson was charged with manslaughter.

The Valukas report recounted that five months before Ms. Anderson pleaded guilty to a lesser charge of criminally negligent homicide, G.M. had analyzed her accident and found a problem with the car was to blame, not her. According to the report, the black box in Ms. Anderson’s car was blank, which the company found to be troubling and indicative of the very defect it had yet to formally identify.

“The most likely scenario for the lack of data and the nondeployment was a power loss,” wrote the G.M. engineer who evaluated the case.

The company settled Ms. Anderson’s lawsuit, as well as the one brought by Ms. Rose’s family.

More definitive evidence of a connection between a problematic switch and a failure of air bag systems was presented to G.M. in 2007. Keith Young, a Wisconsin police trooper, and a team of Indiana University researchers had each reviewed the details and black box data of an Oct. 24, 2006, crash that killed two teenage girls, Amy Rademaker and Natasha Weigel, in St. Croix County, Wis.