Georgia sheriff reopens probe into teen's 2013 death; doctor says initial conclusion 'doesn't make any sense’

A Georgia sheriff has reopened the investigation into the mysterious 2013 death of a high school student found wrapped up in a gym mat.

But eight years later, a new sheriff has reopened the investigation, and the doctor who conducted an independent autopsy told Fox News Wednesday that it was scientifically impossible for the teen to have died as initially described. "Originally it was called ‘positional asphyxia,’" said Dr. William Anderson. "They felt he crawled in down the gym mat and into the middle of it, to try to get a sneaker -- which of course doesn’t make any sense because all you’d have to do is knock the gym mat over on its side, and the sneaker would be at the bottom." Positional asphyxia, Anderson said, happens when someone is trapped in a way that they can’t breathe properly, then suffocates as their muscles grow exhausted and can’t overcome the pressure on their chest. It can take hours, and the evidence would be obvious, he said -- but the state's autopsy showed Johnson's lungs were "basically normal."