PORTLAND, Ore. (Reuters) - The integrity of a federal court jury was called into question on Tuesday as the panel deliberated for a third day in the trial of seven people charged with conspiracy in the armed takeover of a U.S. wildlife center in Oregon this year.

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The issue came to light when the 12-member panel sent a handwritten note to the presiding judge stating that one juror had professed being “very biased” at the start of deliberations last week, citing his past employment with the federal Bureau of Land Management (BLM).

The letter, a copy of which was shown to journalists by defense lawyers, did not make clear whether the juror’s supposed bias was for or against the accused.

The defendants contend their occupation of the Malheur National Wildlife Refuge in eastern Oregon was a legitimate act of civil disobedience protesting control exercised over millions of acres of public land in the West by various federal agencies, including the BLM.

The government has countered that the militants’ leader, Ammon Bundy, and five other followers engaged in a lawless scheme to seize federal property by armed force during the 41-day standoff, which began in early January.

The six men and one woman on trial are charged with conspiracy to impede federal officers through intimidation, threats or force, as well as with possession of firearms in a federal facility and theft of government property.

Each faces up to six years in prison if convicted of conspiracy alone. A separate handwritten jury query to the judge on Tuesday indicated panelists were close to a verdict on some defendants, on some charges, but were split on others.

The newly raised scrutiny of a juror’s impartiality could prolong deliberations and even pave the way for a mistrial or appeal.

U.S. District Judge Anna Brown interviewed the juror privately on Tuesday and said afterward she found “no basis” for determining he was biased. He had disclosed during jury selection that he was employed by BLM roughly 20 years ago.

Brown also agreed with prosecutors that further questioning could undermine the sanctity of jury deliberations, which are supposed to remain private.

But defense lawyers urged the judge to consider further interviews to determine whether the panelist in question should be disqualified and replaced by an alternate before deliberations proceed.

“If we do not get to the bottom of this ... we’re inviting a mistrial down the road,” Bundy’s lawyer, Marcus Mumford, said.

Brown instructed both sides to present arguments for and against further jury interrogation on Wednesday.