For a claim in the form of:
Is the (potentially negative) fact F about a person P true?
Is the following answer's conclusion considered valid? (and if not, what would be the conclusion that is legitimately supported by supplied level of evidence?)
According to an interview with person P themselves, they have stated that the fact F is false
Specific properties of the answer that I'd like to highlight are:
This first person response from person P is the only evidence cited
Person P has a plausible motivation respond with "false" no matter what the actual truth is (e.g. if it were true, they would look worse off to other people).
As @Sklivvz noted, this can be somewhat subjective, but not always (in other words, a reasonable person can be reliably assumed to be motivated to NOT want to admit to being a criminal, or to have failed in some endeavour/life using a well established criteria). Basically, the point here is to establish that there may be a plausible reason for the person to NOT tell the truth in the interview, in which case the onus is on the answerer to prove the facts to be as stated.
Fact "F" in the first-person response is subjectively defined (as an example, the interview asks if a person is "successful", or "wealthy/poor", etc... without any definition of what that means).