First of all, in the legal context, clear and convincing evidence is commonly defined in the context of instructions given to a jury. Here is one common definition in the form of a jury instruction:
Thus, a party cannot meet the burden of establishing <state cause of action> by simply producing evidence which is slightly more persuasive than that opposed to it, which would meet the burden of proof under the preponderance of evidence standard. Instead, the party must produce clear and convincing evidence which is evidence that is substantial and that unequivocally establishes the elements of tate cause of action>, which I shall shortly explain to you. Clear and convincing evidence is evidence that establishes for you a very high probability that the facts asserted are true or exist. See Connecticut Civil Jury Instructions.Here is another definition:
The clear and convincing standard requires evidence of such convincing force that it demonstrates, in contrast to the opposing evidence, a high probability of the truth of the fact[s] for which it is offered as proof. To be clear and convincing, the evidence must be so clear as to leave no substantial doubt and be sufficiently strong to command the unhesitating assent of every reasonable mind. See Sample Instruction.It is not sufficient that the person presenting the evidence be convinced that the evidence is clear and convincing, it is necessary that the judge and the jury also believe it to be. Now, here is the rub, who acts as judge and jury in the genealogical context? It is all well and good to talk about such a standard, but how is it obtained?
The Board for Certification of Genealogists explains the Genealogical Proof Standard (GPS) as follows:
The GPS reflects a change from the term "Preponderance of the Evidence," used earlier to describe the high standard of proof BCG had always promoted. (For further information about this topic, click here for information on BCG's decision and here for a detailed article on this subject.) Case studies in national genealogical journals, such as the National Genealogical Society Quarterly and The American Genealogist, illustrate the GPS.For example, the first element of the GPS is a reasonably exhaustive search. Who determines whether or not the search is "reasonably exhaustive"? If the researcher is the one making the determination, then there is, in effect, no standard.
Although it is convenient to think about the "preponderance of the evidence" standard being raised to the higher "clear and convincing proof" standard, this is not really a viable concept given the requirements of an adversarial proceeding and the decisions made by judge and jury in the legal setting. I suggest that as genealogists, we simply rely on the GPS without direct reference to the legal standards which do not really apply to our individual work.