For bugg smasher, your question is difficult to answer, given that the law of evidence is a vast topic and, in any event, differs according to the applicable legal jurisdiction. It is simpler for me to say that if you want to provide me with some examples of what kind of evidence you wish to offer up, I might be able to offer you some guidance as to whether or not it would be admissible in a UK court.
For ducksoup and JJ, on the subject of a pilot "breaking contract", I suppose you are both right to some degree. JJ's "leaving before one's training bond is amortized" and ducksoup's "not giving the contracted notice period" might, in some circumstances, lead to allegations as to contract breaking. The point, though, is that such acts by a pilot may be perfectly reasonable and justifiable in the relevant circumstances. It seems less than equitable, then, that a pilot should be shunned, blacklisted, whatever, merely on the basis of an employer's unproven allegation as to contract breaking, or, as I understand is alleged in some cases, "bond-jumping".
[ 09 August 2001: Message edited by: Holt CJ ]