After nearly nine years in prison on an "eco-terrorism" conviction, Eric McDavid was released from prison on Thursday after documents obtained by his attorneys revealed the US Federal Bureau of Investigation withheld evidence during trial.

McDavid, 37, was arrested in January 2006 for his participation in a plot by environmentalists to bomb the Nimbus Dam, near Folsom, California, among other targets. The government's case centered on intelligence gathered from an informant named "Anna," who befriended McDavid and two other eco-activists in the mid-2000s. She provided them with food, transportation, and a cabin in Northern California fitted with FBI audio and video equipment.

Soon after, Anna began to question the groups' protest tactics, saying they weren't sufficiently confrontational and began to suggest that they adopt more radical tactics. She bought supplies for assembling homemade explosives and suggested they carry out bomb attacks. If the group questioned her plots or their plans seemed to be progressing too slowly, she berated them.

Photo by McDavid Family

McDavid received a 20-year prison sentence in May 2008. Following his conviction, however, a FOIA request filed by his supporters turned up 3,400 pages of documents that were withheld by the government during trial. The FBI turned over 2,500 pages of documents, including correspondence between McDavid and Anna that revealed he had romantic feelings for her. In one communication McDavid wrote that he wanted to leave activism and build a future with Anna.

Ben Rosenfeld, one of McDavid's attorneys, told VICE News that Anna used these feelings to manipulate McDavid, leading him to believe there would be "time for romance" after the mission had been completed.

"This is an egregious case of government and official misconduct, and it's been a Kafkaesque nightmare for Eric and his family," Rosenfeld told VICE News. "If people think this can't happen in this country, they should think again."

In an agreement with the US Justice Department, McDavid pleaded guilty to a general conspiracy charge with a maximum sentence of five years, in an exchange for waiving any claims for civil damages.

"He never should have been arrested, charged, convicted, or done this much time," Rosenfeld told VICE News. "Frankly, he shouldn't have had to plead to a new felony charge yesterday just to get out of prison."

But McDavid's case, says Rosenfeld and some environmentalists, reveals a broader government program to survey, infiltrate, harass, and jail environmental activists across the country, oftentimes comparing them with radical Islamic jihadists. It's an episode that many environmentalists describe as the "Green Scare."

In 2010, a report from the Justice Department's Office of the Inspector General found the FBI had improperly investigated individuals associated with domestic activist groups, including extending investigations without good reason and keeping domestic terrorism files on acts of nonviolent, civil disobedience. In one case, the agency kept details on a public antiwar rally in a "special events" file, against the guidelines of both the Attorney General and the FBI.

The situation became worse after September 11, Floegel said, particularly in cases where activism brushes up against corporate interests.

"We've had our offices invaded, we've had our phones tapped, we've had our computers hacked," Mark Floegel, research director for Greenpeace, told VICE News. "The FBI is hiring itself out as a private thug force for American corporations."

Rosenfeld said political dissent is the object of the Bureau's activities, rather than just individual suspects.

He told VICE News: "The FBI, at least with respect to anarchists and radical environmental activists, has been intent on chilling people into inaction and destroying individual lives for the incredibly cynical purpose of making examples of people and trying to scare the community."