Letson has signed an affidavit with his testimony as to the events of that day. I bet if you examine his service record, he will be on record as having been assigned to that post as the only doctor at that hospital who could've seen the injury. I bet that if they examine the records for that facility and the recollections of the standing procedure, Letson's memories will be vetted.
Letson was on Hannity the other day and did say that he was the only doctor available. He became very emotional while discussing this. You could tell that he didn't enjoy exposing Kerry but felt that it was his duty with the info that he has.