Sister Megan Rice, Michael Walli and Greg Boertje-Obed gained entry to a Unites States nuclear weapons installation.

 KNOXVILLE, Tenn. - Jurors could begin deliberating Wednesday the fate of a now 83-year-old nun and two other peace activists charged with damaging U.S. government property last year at a secure defense facility where enriched uranium for nuclear bombs is stored.

All three defendants - Sister Megan Rice, who was 82 at the time of the incident, Michael Walli and Greg Boertje-Obed - took the stand in the Knoxville federal court trial before the defense rested its case on Wednesday.

Closing arguments were set for Wednesday afternoon, followed by instructions to the jury in the trial before U.S. District Court Judge Amul Thapar. Prosecutors and defense attorneys presented a total of about 1-1/2 days of evidence in the trial.

A witness for the prosecution testified that the activists disrupted operations, endangering U.S. national security, in the July 2012 break-in at the heavily guarded Y-12 National Security Complex in Oak Ridge, Tennessee, the primary U.S. site for processing and storage of enriched uranium.

Another prosecution witness said the physical damage to the facility cost more than $8,500 to repair.

The activists are accused of cutting several fences, walking through the complex for hours, spray-painting slogans and hammering on the walls of the facility. When guard Kirk Garland confronted them, they offered him food and began singing.

Defense attorneys said the activists, who belong to a group called Transform Now Plowshares, had taken part in a symbolic break-in that did not harm the facility.

“Every moment as we sit here now is an imminent threat to the life of the planet,” Rice testified on Wednesday.

Walli, a Vietnam veteran who described himself as indigent, said, “I can never do enough,” while Boertje-Obed said it was “a miracle” that they could walk from a church parking lot over a ridge and reach the building deep inside the facility grounds.

Defense attorneys also presented a retired Army colonel as an expert witness who testified on Wednesday that the incursion onto the facility grounds helped the government by exposing lax security, which has been improved since then.

Steven Erhart, site manager for the Y-12 National Security Complex and a prosecution witness, on Tuesday said under cross-examination that the breach pointed to “systemic issues and problems with security that should have been detected.”

The breach sparked investigations by the U.S. Congress and the Energy Department, which oversees nuclear facilities. An Energy Department inspector general report in August found “troubling displays of ineptitude” at the complex.

Shortly after the incident, the top security official at the National Nuclear Security Agency and two other federal officials were reassigned. Also, top officials at WSI, the international security company that provided security at Oak Ridge, were removed and officers were fired, demoted or suspended.

If convicted, the activists face up to 20 years in prison on the charge of damaging a national defense premises and 10 years for causing more than $1,000 damage to U.S. government property. - Reuters