Gilbert Levin, the PI for the Labeled Release experiment, is an engineer, with an MS in Sanitary Engineering, and a PhD in Environmental Engineering. He was not a NASA employee. It has been suggested that NASA's extraordinary reluctance to admit the success of the Labeled Release experiment is due to snobbery and envy at NASA's upper management level. If they can only keep delaying until Levin dies (he's quite old now), he won't win the Nobel and embarrass NASA's chemists and biologists.
http://www.gillevin.com/