My own feeling about recovering memories is that if they begin with a lot of feelings - emotions, feeling trauma in my body (somatic memory, for example feeling like I'm activated and buzzing or trembling inside, or actually shaking on the outside), feeling sick and faint etc, these seems a very good indicator that the memory's reliable. If what's remembered was more like a story, more in my head - this happened, then that happened etc - i'd be doubting it more.

There's an article I saw recently that says the same thing. It's about trauma relating to childhood abuse but the focus is on recovering trauma memories so I think it applies to any trauma.
http://www.tandfonline.com/doi/abs/1...99730903318467

I'm not sure if you're talking about a memory of something physical that happened (witnessing something, or physically feeling something). It's also possible to get memories of what happened for you psychologically at the time. But I won't go into that in case that's not what you mean. Thought I'd just mention it.