There is a big gap between having evidence and proving your case. A common scenario when beginning a lawsuit, is to have a client bring in a big box of papers believing that this is the "evidence" that will "prove his case." Basically, the client is starting at the wrong end of the process. But it is nice to have the documents at the beginning of the case, I remember one big trial, where the client decided to bring in thousands of documents two or three days before the trial. Unfortunately, the client did not follow instructions and nearly all of what he brought in was either inadmissible or simply irrelevant.
If you want to prove a fact, you need to understand what "proof"means. In the context of a court hearing or trial, proving a point means meeting the burden of proof on a certain issue. Let's use an example from genealogy. Suppose I want to prove something simple, like a date of birth for an ancestor. If I were proving that fact in court, I would either need a document that was admissible for that fact or testimony from a witness who had some actual knowledge of the subject. The burden of proof is to produce documentary or testamentary evidence in court supporting your claim.
The probability of a document depends on when, how and for what purpose the document was created. The "best evidence" rule requires that the most reliable evidence must be used if it is available. So how would I prove a birth date? The question is "What would prove that Ancestor Roe was born on a certain date? Now back to my client's big pile of documents. If what we are trying to prove is a certain birth date, then only documents dealing with Ancestor Roe's birth are relevant to the issue of the date. No matter how valuable my client thinks the other documents are, unless they speak to the issue of the Ancestor's birth, they are essentially irrelevant. So we search through the records.
What do we find? We find a school report card for the sixth grade. We find an Army Discharge Record. We find a marriage certificate. We find a death certificate with a birth date recorded. (I assume none of these records had a birth date, other than the death certificate) But my client says that the date is wrong. When I ask him why the date is wrong, he says that he heard from his mother that they put the wrong date on the death certificate. He says that he believes the date to be six months earlier than that reported on the death certificate. I tell the client that none of the evidence he has is very good and unless we can come up with something better, we have a poor chance of proving our case in court, especially since the date on the death certificate if correct proves the opposing side's case.
My client says, why doesn't he just testify about the date on the death certificate. I tell him that, the court (judge) may or may not allow his testimony because of the rules of evidence on what is called hearsay. But even if the judge does allow the testimony, it is unlikely that the judge or a jury would find his testimony persuasive.
I suggest we do some more research and look for additional documents. We really aren't ready to go to court until we find something that establishes a birth date consistent with my client's claim. But if that is all we have. We may just have to live with the uncertainty and take our chances. The client then asks, but what happens when the other side of the lawsuit puts on their case and proves the date on the death certificate is correct? What do we do then? Exactly, I say, I remind him that inheriting the huge multimillion dollars estate all turns on the exact date of birth of Ancestor Roe, so unless we can prove the date exactly, we lose.
Now we have to know something about the way courts work today. In times past, in the ancient days of Perry Mason, you found out about your opponent's case in court. I made for a lot of stomach acid and surprises. Now there are rules in place in most cases and jurisdictions that require full disclosure of all the evidence you are going to use before you go to trial and, like my example above, if you produce the evidence too late in the trial process, you may not be allowed to use the evidence at all in court.
So back to the trial about the birth date. The opposition sends us their disclosure statement and they have a only friend of the deceased who is going to testify that he attended the deceased's 50th birthday party on such and such a date and that the date is consistent with the date on the death certificate. If that is the testimony, it is highly unlikely that what my client has will persuade either the judge or jury. Will the judge allow the opposition's witness to testify? Yes, very likely. If the judge or the jury believes the testimony, we will lose our case. In order to win, we have to come up with some evidence even more reliable than the witness that proves the date we claim is the birth date and to disprove the date on the death certificate. By the way, we have an uphill battle because the death certificate is a government document.
We go back to do some research and since we know that Ancestor Roe was in the Army. We get his draft registration card from Ancestry.com or FamilySearch.org. There in his own handwriting is his date of birth. Do we win or lose? Hmm. Could go either way depending on the date. I will let you decide.
Fortunately, in most instances in genealogy, the stakes are not quite so high concerning the proof of a date or place or whatever. But an exact date could be extremely important in proving which of two Roes was the ancestor or some other issue. Also, unlike a court, there is no judge or jury deciding who is right and who is wrong. Our genealogical conclusions depend on the court of public opinion, our relatives and our peers. But the principle is the same. It is important to have evidence that is probative of the issue and the best evidence is usually the most probative.
I plan on continuing this discussion to include more about the burden of proof and the burden of persuasion.