Many can't remember details from last week and decades-later memories are to be taken with a bag of salt......,
..., I'll take it with a bag of salt as most would be 2nd or 3rd person recollections already "colored" by having been filtered through someone else's memories...
..., And then we have "eye-witness" testimony to crimes where the witness was completely wrong. Memory is plastic...
Memory is plastic for a population; one cannot predict for the individual. I deal with first person accounts acquired immediately after crimes have occurred, as well as those collected days, weeks, or months after...perhaps years. Some are by witnesses, and some are by victims. Some are so bad I have to ask "are you sure you were there?". Some are so accurate they give chills down the spine to a defense attorney. Today we have the luxury of physical data, sometimes, to confirm or dismiss the information in first person accounts, because several first person accounts of the same event in no way overcomes the problems and possible flaws of a first person account.
Yet from all that you've written, you can't really accept any first person accounts, whether journals written within minutes of the event or memoirs done some time after the event. So what's the point of looking for a first person account when there is no physical archaeology or preserved artifacts to confirm the account?
LD