If the US state wins, it will be the first case in the world to successfully prosecute a fossil fuel company for greenwashing and misleading the public.
How much is the fossil fuel industry actually doing to tackle climate change? If you listen to the companies themselves, quite a lot.
The firm claims it could “one day power planes, propel ships and fuel trucks and cut their emissions in half”.
But not everyone’s buying it.
And – partly because of that – Exxon and other oil companies are fighting various forms of legal action across the US.
But it’s partly because of what climate change is doing to the people of Massachusetts, that the state decided to take Exxon to court.
Bruce Silverbrand is a shell fisherman and oyster farmer who’s been working on the waters around Bourne, at the gateway to Cape Cod, all his life.
He is worried – the tides have also changed and the weather is becoming more extreme.
“You would think that the company’s primary business is saving the world,” says Karen Sokol, a law professor at Loyola University, New Orleans.
In a statement, it also said the case against it has no merit.
I don’t think I’ll ever see anything out of it,” he says.