In December of 2011, I was invited to speak to the police concerning a former roommate of mine who has been accused of murder (and posted a question concerning that here on the site). Just this week, I received a notification that I am to appear again, this time in court, to testify as a witness. Having heard horror stories of people with faulty memories being imprisoned for a year or more because they provided false testimony without knowing they did so, or because their testimony didn't overlap with what they told the police, I am now very worried (I am an expat living in Germany, and I've not yet been able to talk to a proper lawyer to determine how strict the laws concerning court testimony are). Perhaps that is somewhat narcissistic of me, given the circumstances, but the fact remains. I wonder, then, what kind of "truth" I am supposed to tell the court. The truth seems to be that I *believe* that my former roommate behaved in way X, spoke of topic Y and didn't speak of Z, with my only justification being that that's how things seem in my memory - which, given the 2-3 years since the time I lived with that roommate, may well be faulty. Is my belief that something happened because my memories say it happened justified? Or is the only truth that "I, based on my potentially faulty memory, hold the potentially false belief that [such-and-such] happened?" I think it might be best to preface everything I say with "I believe that... As far as I can remember, it seems... I'm not sure, but I believe that..." Is that a valid way of circumventing the problem of not knowing whether I can trust my own memories?