The New York attorney general is taking ExxonMobil to trial in a historic case Tuesday, accusing the oil giant of misleading investors about the company’s financial risks due to climate change.

Under the direction of Attorney General Letitia James, this is the first climate fraud lawsuit to go to trial in the United States. James is acting under New York’s Martin Act, a 1921 anti-fraud law meant to protect investors against false statements, even ones made without proof of intent to deceive.

The historic lawsuit comes as more and more legal action is being taken against Exxon and other fossil fuel companies by cities and states seeking to hold them accountable for their contribution to climate impacts.

The trial, which will take place before the judge and not a jury, will begin Tuesday at 2:15 p.m. EDT in the New York Supreme Court, and could last up to three weeks. Climate activists plan to rally outside the court ahead of the trial to draw attention to it. It is possible that Exxon’s former chief executive Rex Tillerson, who left the company to serve as President Donald Trump’s initial secretary of state, could testify. New York’s investigation previously revealed Tillerson used a second secret email address as the company’s CEO.

New York prosecutors began their investigation about four years ago and sued Exxon last October. Under the direction of Attorney General Eric Schneiderman, who later resigned amid a harassment scandal, in November 2015 New York issued its first subpoena to Exxon demanding documents on the company’s internal accounting on climate risk.

The investigation followed parallel investigations by InsideClimate News and the Los Angeles Times showing how the oil company’s own researchers confirmed that fossil fuels have contributed to global warming in the 1970s and 1980s. (Subsequent reporting revealed oil researchers were studying climate change back in the 1950s.) The information about Exxon’s climate research threw the company’s later efforts to cast doubt on climate science and fund misinformation campaigns into sharp focus.

“Exxon has been working very hard to prevent this day from ever happening,” Michael Gerrard, director of Columbia University’s Sabin Center for Climate Change Law, told BuzzFeed News. They’ve brought lawsuits in both federal court and state court to halt or delay action on the investigation, and waged a public relations campaign, he added.

The allegations, explained

The crux of this Exxon case hinges on whether they were keeping “two sets of books,” said climate activist Kert Davies, who helped expose Exxon’s past funding of climate denial. This would portray climate risk to shareholders “differently in public than they are behind closed doors.”

The New York attorney general declined to comment, instead pointing BuzzFeed News to a pretrial memo filed on Oct. 7 that spells out Exxon’s alleged deceit. In anticipation that governments would adopt aggressive new climate policies including charging companies for their climate pollution, such as carbon dioxide, Exxon said in public disclosures that it was accounting for how a warming world threatened the business.

Specifically, Exxon disclosed to investors “that it was applying a cost of carbon approaching $80 per ton across its business to account for that risk,” per the memo. “But ExxonMobil did no such thing. For many years, ExxonMobil’s undisclosed internal guidance directed its employees to apply a far lower cost of carbon than the company purported to use.”

By claiming to use a higher carbon cost than it actually was, “ExxonMobil made its assets appear significantly more secure than they really were, which had a material impact on its share price,” according to the memo. The New York attorney general estimates the damage to Exxon shareholders ranges from about $476 million to $1.6 billion.

At trial, Exxon is expected to acknowledge it had two sets of carbon costs but will argue investors should have known this and how the different prices were used based on disclosures.

“Reasonable investors who reviewed ExxonMobil's disclosures understood that climate risks factored into ExxonMobil's decision-making, which is all that could have mattered to them. Those investors also understood that ExxonMobil did not disclose the proprietary details about how it weighed those risks,” the company wrote in its own pretrial memo. Moreover, the company accuses the New York attorney general office of finding “no evidence of wrongdoing.”

Company spokesperson Scott Silvestri told the Los Angeles Times the investigations into Exxon were “politically motivated and resulted from a coordinated effort by anti-fossil fuel groups and contingency-fee lawyers involved in other lawsuits against industry.”

Exxon did not immediately respond to a request for comment.