There are many fraudulent accounts from individuals, mainly from the British/colonial side for obvious reasons.
In general, when one tries to evaluate a source from a private individual, it is best to try to cross-reference facts contained within it with other known or fixed points. When things start not to tally then there's something wrong and the source becomes untrustworthy. Zabange and Lyon are good examples of this.
Where the source is an official document or claiming to be one, and the content is dubious, then provenance has to be examined and, if necessary, scientific analysis of the document itself. The Pulleine-Cavaye order and the recent second set of Chelmsford's Instructions are good examples.