AN American man who was captured in Cambodia in March pleaded guilty to second-degree murder in a United States court on Monday, admitting that he killed his 61-year-old mother by stabbing her 17 times, The Associated Press reported. According to the reports, Nathan Helburn, 34, was captured on March 18 after being traced to Cambodia and sent back to his home state of Idaho on March 23 by US federal agents. He was initially charged with first-degree murder before a plea bargain agreement was reached. Sentencing in the case is scheduled for November 1.