Aaron Hernandez Pleads Not Guilty To Beating Handcuffed Inmate, Challenges Evidence

Aaron Hernandez talks with one of his defense attorneys, Charles Rankin, during a hearing on Monday, June 16, 2014, in Fall River, Mass. (AP)

FALL RIVER, Mass. – Former New England Patriots' tight end Aaron Hernandez pleaded guilty Monday to charges that he attacked a handcuffed inmate and threatened to kill a guard and his family while at a county jail in Dartmouth, Massachusetts.

Hernandez is charged with murder in three killings.

The plea came Monday, the same day his lawyers asked a Massachusetts judge to dismiss a murder charge in the 2013 slaying of semi-pro football player Odin Lloyd. Defense attorneys say the charges should be dismissed because prosecutors have failed to show probable cause that Hernandez killed Lloyd or even took part in the slaying.

Prosecutors countered that they have "powerful evidence" against Hernandez that bolsters their case.

The judge did not immediately rule.

Hernandez also is charged with killing two men in Boston in 2012. He is being held without bail.

Based on reporting by The Associated Press.