Los Angeles, California (CNN ) -- When former in-house defense attorney Dimitrios Biller resigned from his top post at Toyota, he walked out with something potentially more valuable than his nearly $4 million severance package.

He took some 6,000 internal documents, including memos and e-mails potentially damaging to his former employer.

"Not potentially, they are. They are very damaging," Biller said.

Biller, now entangled in litigation with the auto giant, defended the company in product liability and negligence cases from 2003 to 2007. He says he quit because of what he alleges were "criminal acts" by Toyota -- specifically, withholding information the company was legally required to turn over to plaintiffs' lawyers during litigation.

"There is a regular pattern and practice of not producing memos, minutes, reports, and e-mails," Biller said. "These documents can be used to establish liability against Toyota in product liability and negligence cases."

The documents -- some of which were reviewed by CNN -- were sent by Biller to Toyota officials. There are numerous references to so-called "Books of Knowledge," highly confidential information on design, safety systems and testing records allegedly generated by Toyota engineers on everything from roll-overs and roof safety to sudden unintended acceleration.

The chairman of a U.S. House committee investigating Toyota seems to agree with Biller, saying Toyota engaged in a "systematic disregard for the law and routine violation of court discovery orders in litigation."

Rep. Edolphus Towns, D-New York, whose committee subpoenaed Biller's documents, said "The material, I must admit, is very, very disturbing."

Toyota defends its actions, saying, "We are confident that we have acted appropriately with respect to all product liability litigation."

Yet so far, the company has fought to keep the documents confidential and away from court cases -- like Pennie Green's. The Texas native was 17 and driving to see a movie with her cousin when her life instantly changed.

"I didn't make it," she said.

A car turned in front of Green and, with no time to react, her 1997 Camry swerved, rolled over and landed upside down. "When I opened my eyes, my nose felt like it was almost touching my belly button I was so curled up."

Green never walked again. In 2005 she filed suit against Toyota, claiming the roof was defective because it didn't withstand the weight of the car like it should have.

Biller defended Toyota in that rollover case, brought by Green's lawyer, Jeff Embry.

"We certainly requested everything that had any relevance to our case at all and, in fact, we had to go to the court to have Toyota ordered to provide their information," said Embry, who added Toyota provided just enough information to show Toyota vehicles "met the minimum standards."

Green's case settled in 2006 for $1.5 million.

Included in Biller's documents is an e-mail he said he sent to his bosses summarizing negotiations. It says, "TMS [Toyota Motor Sales USA] concluded that it would be better to pay a premium to settle this case and avoid producing the 'Books of Knowledge.'"

Embry said he had no idea how close he'd come to uncovering Toyota's alleged secrets. "I think they were very careful to keep design information, very important information in Japan, out of reach of our system as much as possible," he said.

Although Toyota calls the materials "trade secrets," Embry said, "That doesn't mean that you get to keep them a secret from the court system."

So why, if Biller knew a judge had ordered all information produced, didn't he produce it? He said he tried but was stopped by a superior who told him, "You have to protect the client at all costs."

"Even if that includes," Biller asked, "committing criminal acts or violating the law?"

The answer, Biller said, was yes.

Did he break the law? "No, I did as much as I could as a lawyer for a client to not break the law," he said. "I wrote e-mail after e-mail, memo after memo, explaining the legal obligations Toyota and its affiliates needed to fulfill."

In response to Biller's documents and his allegations, Toyota spokeswoman Cindy Knight released this statement: "Mr. Biller continues to make inaccurate and misleading allegations about Toyota's conduct that we strongly dispute and will continue to fight against vigorously."

Before leaving Toyota four years ago, Biller had a nervous breakdown caused, he said, by stress. Still, he said, he is confident his e-mails left a trail showing he tried to change Toyota.

"The documents speak for themselves. I know what happened. I know exactly what happened. I know the names of the people who were responsible for it. I know where the skeletons are hidden."

As for Pennie Green, if a judge finds Toyota did hide documents, she said, "all I want is justice for that. They just need to take responsibility for their actions."

Embry has filed a motion in Texas with the state's 18th District Court to investigate whether Toyota unlawfully withheld evidence in Green's case and should be held in contempt.

So far Toyota has fought successfully to keep Biller's documents sealed and Biller from testifying.