A mother and father will serve well over a decade behind bars for breaking their baby’s leg.The couple, Dara Ann Dillard Cooper and Jonathan Randall Cooper, both entered guilty pleas before Circuit Court Judge Bart Stanley to charges of aggravated child abuse. They were both ordered to serve 15 years in prison at a minimum of 85 percent before they are eligible for parole.“It’s a horrible case,” said McMinnville police detective Todd Rowland of the horrific fracture sustained by the 2-month-old infant at the hands of one of his parents. Neither parent took responsibility for the injury after the diagnosis.The infant was taken to Vanderbilt Children’s Hospital where doctors said it had suffered a spiral fracture to one of its legs, the result, experts say, of a twisting motion.