After three years of litigating, the state of Massachusetts is about to find out what ExxonMobil knew about the connection between fossil fuels and global warming–and when. On Monday, the Supreme Court refused a petition to hear the #ExxonKnew case. Instead, the Court opted to let stand a ruling from the Massachusetts Supreme Judicial Court from April 2018.

This means that Exxon will now need to begin digging through records dating back as far as 1976 in response to Massachusetts Attorney General Maura Healey’s records requests. This will take time, since many of the records have not been digitized.

Now the question is, what does Healey expect to find?

“The decision by the U.S. Supreme Court to not take this case does not change the underlying problems with Attorney General Healey’s investigation,” said National Association of Manufacturers (NAM) Senior VP and General Counsel Linda Kelly, calling the investment a “misguided political effort” and a “waste of Massachusetts’ tax dollars.”

“The New York Attorney General’s office brought essentially the same investigation in 2015, received millions of documents from the company, and failed to find a smoking gun.”

Working under a similar premise as Massachusetts, then-New York Attorney General Eric Schneiderman spent nearly three years investigating the company. Over the course of this lawsuit, Exxon was forced to produce more than 4 million pages of documents and nearly 200 hours of testimony by 18 witnesses.

After all this, the investigation failed to uncover any evidence directly pointing to a coverup. By the end of the summer, even judges were beginning to express frustration over the many information request motions and the Attorney General’s failure to file a case.

Telling the attorneys that the requests could not go on “interminably,” New York Superior Court Judge Barry R. Ostrager told the AG’s office that they needed to work toward a prosecution or drop the case.

“The company has provided millions of pages of documents and answered questions over some three years of investigation,” he said. “It’s not my place to tell you when an investigation ends, but it is my place to put an end date on the requests for information and the filing of a complaint.”

In late October. New York eventually did file a suit against Exxon, alleging that Exxon had misled investors about the risks climate change regulations posed to its business. This was far less than many supporters had hoped for, especially given the AG’s broad access to company documents.

It’s uncertain if Massachusetts will find anything better. Under the terms of a Common Interest agreement that New York and Massachusetts signed in 2016, the New York AG’s office should have been able to share any documents it obtained with its counterpart in Massachusetts.

Even if Massachusetts is able to file a lawsuit, its odds of winning are uncertain. The Securities and Exchange Commission (SEC), which also reviewed company documents, came to a similar conclusion as New York, finding that the company had not misled investors.

Industry observers see the cases as a means of putting pressure on energy companies without necessarily building towards a case. The sheer volume of requested records and the shifting terms of what the AGs were looking for has cost Exxon time and money and will likely be a warning to other companies.

“These investigations were designed to put energy companies on notice that if they dared to disagree with certain elected officials on climate policy, they would be met with abuse and harassment,” says Spencer Walrath, of Energy in Depth.

“Though these public officials may be frustrated over what they perceive as federal inaction on climate change, targeting law-abiding companies with arbitrary investigations only deters future investment in the state, to say nothing of it being a poor use of taxpayer resources.”

Ironically, the #ExxonKnew legal saga is coming to an end even as environmentalists in some of the same AG’s offices are already at work on new tactics. Rather than trying to find evidence that energy companies covered up information about the connection between fossil fuels and global warming, cities and some state governments have filed public nuisance suits against oil companies in an attempt to make these companies pay for costs associated with global warming.

Follow Erin on Twitter.