A federal judge declared a mistrial Wednesday in the case of a Nevada rancher accused of leading an armed standoff against the government in 2014, blaming prosecutors for withholding key evidence from defense lawyers, including records about the conduct of FBI and Bureau of Land Management agents.

Chief U.S. District Judge Gloria Navarro in Las Vegas dismissed a jury seated last month for the long-awaited trial of Cliven Bundy, his sons Ryan and Ammon Bundy and self-styled Montana militia leader Ryan Payne.

The decision is the latest in a string of failed prosecutions in Nevada and Oregon against those who have opposed federal control of vast swaths of land in Western states.

Jurors acquitted the two Bundy sons of taking over a federal wildlife refuge in Oregon for more than a month in early 2016 and amid calls for the U.S. government to turn over public land to local control.

In the Nevada case, Navarro faulted federal prosecutors for failing to turn over all evidence to defense attorneys.

"The government is obligated to disclose all evidence that might be favorable" to the defense, the judge said.

The case stemmed from an armed confrontation that capped a decades long dispute over Cliven Bundy's refusal to pay grazing fees. The 71-year-old rancher says his family has grazed cattle for more than a century in the area and insists public land belongs to states, not the U.S. government.

CLIVEN BUNDY REFUSES TO LEAVE JAIL AMID ONGOING TRIAL

Government agents began rounding up his cattle. The four on trial were accused of enlisting armed gunmen to force government agents to abandon the effort.

The judge had hinted last week that trouble was afoot. She sent the jury home to review sealed documents following closed-door hearings over complaints about the conduct of FBI and Bureau of Land Management agents during the standoff.

Jurors got a glimpse of the claims when Ryan Bundy, who represented himself, spoke at opening statements about seeing government snipers and surveillance cameras positioned on hilltops surrounding his family home in the days before armed supporters answered his family's calls for help.

A whistleblower memo by a lead U.S. Bureau of Land Management investigator that was released last week alleges widespread bad judgment, bias and misconduct, as well as "likely policy, ethical and legal violations among senior and supervisory staff" in the days leading up to the standoff.

The memo said agents who planned and oversaw the cattle roundup mocked and displayed clear prejudice against the Bundys, their supporters and Mormons.

The investigator, Larry Wooten, said he was removed from the investigation last February after he complained to the U.S. attorney's office in Nevada.

The judge freed the Bundy sons and Payne to house arrest during the trial after nearly two years in jail. Cliven Bundy refused the judge's offer, with his lawyer saying the patriarch was holding out for acquittal.

"A mistrial is a very bad result for the government," Ian Bartrum, a University of Nevada, Las Vegas, law professor who has followed the case closely told the Associated Press.

Bartrum had cast the trial as a test of whether the federal government could enforce its own land policy in Western states where it owns or controls vast expanses.

Acting U.S. Attorney Steven Myhre had no immediate answer when asked by the Associated Press about whether prosecutors would retry the case, but according to Reuters, a new trial date was set for Feb. 26, 2018.

In a new trial, the Bundys and Payne still would face 15 felony charges including assault and threats against federal officers, firearms counts, obstruction and extortion.

Prosecutors also failed to win full convictions against others at the tense confrontation near Bunkerville, about 80 miles northeast of Las Vegas.

Six men who acknowledged carrying assault-style weapons faced a trial and a retrial. Two were acquitted, two were convicted of some charges and two are free after pleading guilty to misdemeanors to avoid a third trial. None was found guilty of conspiracy.

Payne had pleaded guilty in July 2016 to a felony conspiracy charge before trial in the armed takeover of the Oregon wildlife refuge. He's now fighting to withdraw his plea and his expected sentence of more than three years in prison.

The Associated Press contributed to this report.