NASHVILLE, Tenn. (AP) Jury selection is getting underway for an octogenarian nun and two co-defendants accused of intruding into a national security facility in Tennessee that has had a hand in making, maintaining or dismantling parts of every nuclear weapon in the country's arsenal.

Authorities say that in July, Sister Megan Rice and Michael Walli, both of Washington, D. C., and Greg Boertje-Obed of Duluth, Minn., used bolt cutters to cut through fences and spent about two hours inside the Y-12 National Security Complex.

According to court records, they splashed human blood on the walls of fortress-like Highly Enriched Uranium Materials Facility.

The activists have argued in court filings that their refusal to plead guilty to trespassing led prosecutors to enhance charges that could lead to 20-year sentences if they are found guilty.