The General Motors’ (GM) litigation department knew about the fatal ignition switch flaw yet failed to address the safety issues for over a decade now, which is why U.S. senators on Thursday are pressing the automaker’s CEO Mary Barra to fire its top lawyer and why it didn’t do so in the past.

Recall that GM contracted an internal investigation, conducted by Atty. Anton Valukas, to look into the issue. The results, made public in June, indicated that some officials of the company knew about the problem for years prior to being publicly exposed in February. GM executives, however, found no misconduct and cleared the involved officials.

In a Senate subcommittee hearing, Barra refused to respond to the calls of lawmakers to fire Atty. Michael Millikin, calling the latter as “a man of incredibly high integrity.”

“Unfortunately in this instance it wasn’t brought to his attention,” Barra said in defense of Millikin.

Millikin explained that his subordinates kept him in the dark regarding the potential punitive damages GM faces with regard to the ignition switch defect. He said he didn’t know of the safety risks of the defect until early February 2014, just before GM issued the first public recall notice. He added that the lawyers in the April 2013 fatal crash case didn’t take any action to alert the company’s engineers in spite having enough information about the issue.

"That was tragic. If they had brought it to my attention at that time, I certainly would have made sure that they had done something," said Millikin.

Millikin informed the senators that there was already a reorganization of the legal staff to directly report to him. He also said to personally look at the engineering issues that led to serious injury or fatality, which in turn results to a settlement or court trial.

The senators were, however, firm saying Millikin should still be held liable for the company’s lower-level lawyers. The automaker dismissed 15 people in the company, mostly senior officials in the legal and engineering departments, including the lower-level lawyers.

"I do not understand how the General Counsel for a litigation department that had this massive failure of responsibility, how he would be allowed to continue in that important leadership role in this company," Senator Claire McCaskill, Senate Commerce subcommittee chairwoman, said.

McCaskill reiterated Millikin should have been fired, referring to conclusions of the internal investigation. The internal report likewise criticized a corporate culture called “GM nod,” wherein officials would collectively nod in agreement to an action plan but never implement it.

Barra announced during the Senate probe that she will change the internal culture of the company by instigating reforms for more transparency and an attention to safety.

McCaskill will continue to hold hearing in the coming weeks, this time to ask safety regulators in the government regarding their role in said recalls. She also advised Barra to expand the company’s compensation program to victims, who can claim compensation from Aug.1 to Dec. 31.

Ignition switch issues on GM’s product lines have already caused 16 deaths, based on research.