buddy letter
n.— «“We’ve seen people who refused treatment at the time,” she said. “What we advise people is to search for and submit new evidence.”…She said veterans have also had some luck in introducing as evidence what is called “a buddy letter”—a signed affidavit by a witness to the injury.» —“The pain lingers” by Stacy Milbouer Nashua Telegraph (New Hampshire) Oct. 15, 2007. (source: Double-Tongued Dictionary)