In a state where cigarette smoking had sickened and killed tens of thousands of residents, Louisiana Attorney General Richard Ieyoub was getting ready to launch one of the most difficult legal battles of his career.

With billions of dollars at stake, the tobacco industry was already geared up to fight back.

More than a dozen lawyers for the industry descended on the attorney general’s office in March 1996 and made it clear: If he filed suit, they would take steps to derail his political career, he later recalled.

The lawyers said the tobacco companies would not only oppose his planned primary run for the U.S. Senate that year, they would also win whatever case he filed against them.

"They proceeded to tell me that this was a frivolous case," Mr. Ieyoub said. "That it was foolish for me to put my political career on the line. And that they would be wholeheartedly against me."

The day after the tense meeting, Mr. Ieyoub said he filed the sweeping case on behalf of his state, accusing major cigarette makers of concealing the hazards of smoking in what grew into the largest litigation ever waged against the U.S. tobacco industry.

The lawsuit he helped advance with other states was built partly on internal documents from the industry that showed tobacco executives knew as far back as 1963 that cigarettes were addictive and could cause cancer, despite the testimony of the industry's top executives who appeared before Congress in 1994 and said no such evidence existed.

The case would prompt the companies to settle for hundreds of billions of dollars in 1998, cementing Mr. Ieyoub's legacy as one of the state's most impactful attorneys general.

But before his sudden death in April at the age of 78, he would wage another legal battle in a case with striking parallels to his earlier fight and with far more at stake for him personally.

After a diagnosis of oral cancer in 2017 and a painful operation that led to reconstructive surgery of his jaw, he was alerted to the massive recall by the global medical device maker Philips Respironics in 2021 of its breathing machines, including two of the same models that he had used to treat his sleep apnea.

In interviews with the Pittsburgh Post-Gazette and ProPublica before he died, Mr. Ieyoub said he launched his own inquiry with his lawyers into whether the continuous positive airway pressure device that he strapped to his mouth every night to help him sleep may have triggered the cancer.

As he learned more about the company's practices prior to the recall, he decided to file a lawsuit in federal court in Pittsburgh in 2021, accusing the company of selling machines that were dangerously defective. Philips Respironics has two plants near Pittsburgh that make its CPAP and ventilator devices.

Mr. Ieyoub has since emerged as one of the best-known figures to take on the industry powerhouse in a case that now involves hundreds of plaintiffs across the nation.

Long known for tackling tough lawsuits as the top law enforcement agent in Louisiana, he said he was confronting what he called a level of “corporate abuse and dishonesty” that he hadn’t seen in decades and threatened millions of people worldwide.

“The fact that I was involved in the tobacco lawsuit made it even more necessary for me to stand up and try to do what I could to bring about some accountability,” he said.

Mr. Ieyoub, who settled contentious civil rights cases and fought for consumer protections during his 12 years in office, said he was angered when evidence emerged in court that showed Philips had known of the defect in the machines for years but didn’t tell consumers until the recall.

After he filed his case — now being taken up by his estate — he learned that emails showed that Philips engineers were aware as early as 2016 that foam placed in the devices to reduce noise was breaking down into tiny particles.

In a written statement to the Post-Gazette and ProPublica, Philips said "the health and well-being of patients are a top priority" for the company, and "we regret the distress and concern that the Philips Respironics recall has caused to affected device users, including Mr. Ieyoub and his family."

The company said it launched the massive recall two years ago "out of an abundance of caution" and that tests performed by Philips in the wake of the recall now show the foam does not pose any "appreciable harm to health in patients." There is no causal link between the devices and cancer, the company said.

But the Food and Drug Administration, which oversees the medical device industry, issued a statement in October saying tests by the company were not adequate and that further evaluations needed to be done.

Three experts who reviewed the company’s test results for the Post-Gazette and ProPublica said the sleep apnea machines and ventilators tested positive for genotoxicity, the process that causes cells to mutate and can lead to cancer.

"You can’t make the argument that it’s safe. That’s bad science,” said an engineer familiar with the Philips testing.

Mr. Ieyoub said he believed the company “consciously decided not to reveal” evidence the machines were potentially dangerous. "That could have saved a lot of lives or prevented many, many people from having to go through extensive treatment,” he said.

At the time of the recall, Mr. Ieyoub was years into recovery from his bout with cancer that led to a 17-hour surgery at the MD Anderson Cancer Center in Houston, where surgeons stripped back part of his face, removed a piece of his jaw and replaced it with bone cut from his lower right leg.

“I was wondering whether I would be disfigured for the rest of my life,” he said.

Mr. Ieyoub began to piece together the potential connection between the Philips SystemOne and Philips Remstar CPAPs he had been using for years and the cancer that the doctors had removed.

He had never smoked, and the kind of cancer removed from his mouth was frequently found in patients who had used tobacco products, records show.

“I felt like I needed to look further and do a little bit more investigation,” he said.

With every piece of evidence that was surfacing, he said he encouraged his lawyers to keep pressing his case with the goal of uncovering the inner workings of a company that should have made decisions that were "best for the people and not worry so much about profits," he said.

Art Murray, his son-in-law and one of his lawyers, said Mr. Ieyoub was motivated not just by his own case, but by the sheer number of people impacted by the health crisis.

“He got visibly mad,” said Mr. Murray, a New Orleans attorney. "Most people didn't survive what he went through."

In the months before he died April 10 of an aortic aneurysm, he would frequently talk to family members about his battle with Big Tobacco and the similarities surfacing in his own legal challenge against Philips.

"The irony was not lost on me and it wasn't lost on him," said Mr. Murray.

For Mr. Ieyoub, a Democrat who first won public office in 1984 as district attorney for Calcasieu Parish in southwest Louisiana, the fight that he waged more than two decades ago defined him as a person and also took a toll on his political life, said those who knew him.

After he filed the lawsuit against the cigarette makers, joining Mississippi and three other states, the industry poured soft money in campaigns against him, he told The Advocate newspaper in 2003. "I don't know how much, but they did contribute heavily, and it was a very close race," he said.

Just before the Senate primary in 1996, he was accused by the National Republican Senatorial Committee of improperly spending campaign money — allegations he vehemently denied — and was eventually defeated in the race, missing a runoff by 13,586 votes.

The Justice Department launched an inquiry into the campaign expenses and other matters, but eventually ended the investigation with no action taken.

Michael Moore, the former attorney general of Mississippi who first approached Mr. Ieyoub about joining other states in challenging the tobacco companies in 1996, told the Post-Gazette that none of the allegations held up and that they were motivated by politics.

"There was no case," said Mr. Moore. “They tore him and his family apart. I walked step by step with him through all that. It really hurt him because he knew he had not done anything wrong.”

At the time, both the Republican governor, Mike Foster, and the state health secretary, Bobby Jindal, a Republican who was later elected governor, filed affidavits opposing the suit. "It took a lot of courage for him to file at that point, because, you know, he did have a lot of opposition," said Mr. Moore.

Mr. Ieyoub told the Post-Gazette that it didn't matter that some of the top lawmakers didn't favor the litigation. He was moved by two factors: The tobacco companies knew years earlier the products they were selling could cause serious illnesses and concealed it, he said. And he was especially upset over the discovery that the companies were targeting young people using cartoon characters in marketing campaigns.

"One of the results of that lawsuit was to prevent them from doing that kind of advertising. We fought very hard to bring it out," he said.

Mr. Ieyoub's wife, Caprice, an attorney who was married to him for 28 years, said her husband didn’t waver in his stance, despite criticism from some of Louisiana’s powerbrokers.

"He sacrificed so much to serve," she said. "When Richard was faced with tough, hard choices, we used to say if you ever lose your job for doing it, we can live with that."

Ultimately, Louisiana would reap $4.6 billion in the tobacco settlement to be paid over 25 years. In the ensuing years, Mr. Ieyoub would win two more terms as attorney general and lose a close primary race for governor in 2003 before leaving office the next year.

In an interview with the Post-Gazette and ProPublica at his home two weeks before he died, Mr. Ieyoub said that much of his passion for politics was influenced by his father, who emigrated from Lebanon as a teenager and who frequently spoke about the oppression that his family felt because of their Catholic faith.

“He said, ‘Son, you are so lucky to have been born in this country.’ And so that was planting seeds.”

In 2016, the year before his cancer diagnosis, he was appointed by Gov. John Bel Edwards as the state commissioner of conservation, which regulates the oil and gas industry, a post he held until his death.

For much of his career, he said he fought on behalf of constituents, but the last legal battle he waged against Philips was for himself — and even then, he was conscious of the millions of other people whose lives were impacted by the recall.

"To think that so many people are going to have to suffer," said Mr. Ieyoub. "It’s a tragedy."

On April 10 — the day before evidence was released in court that showed Philips’ own tests found the breathing machines posed “unacceptable” risks to patients — Mr. Ieyoub died. His funeral Mass was held at St. Joseph Cathedral in Baton Rouge, where one of the speakers was Mr. Edwards.

He was recognized for his years in public service, with flags flown at half staff and a moment of silence at the state capitol, but his calling was not about ceremony, said his wife.

“He was never willing to even consider not stepping up” when faced with challenges, “and while some saw it as courageous, he just saw it as part of the role he was called to serve.”

ProPublica investigative reporter Debbie Cenziper and Post-Gazette data reporter Michael Korsh contributed to this report.

Michael Sallah: msallah@post-gazette.com; @mikesallah7

Mike Wereschagin: mwereschagin@post-gazette.com; @wrschgn