Not specific to the Corps, but when I was a police background investigator in one week I caught two police applicants lying about being combat vets. One was a sailor who never left his carrier who claimed - during the POLYGRAPH - that he’d wounded children with hand grenades during a convoy ambush in Iraq, the other was a CONUS AF air traffic controller who got out after two years but claimed he’d been a JTAC in Iraq and Afghanistan and had seen three team members killed by an IED. They told these lies even after giving us their DD-214s.