What is evidence?

I have piles and piles of historical records, old letters, e-mails, all of which provide details about my family.

Is all of the information contained in these documents evidence? If not, then how do I go about differentiating between the information and the evidence? What should I do with the information and what should I do with the evidence?

8 Answers 8


Information is only information if it is not used for anything.

Once it is used to support or unsupport some theory, then that information becomes an item of evidence for the theory.

It is like the detective who is looking for evidence. He finds information and throws away anything that isn't evidence - i.e. doesn't support or deny who the killer is.

You have collected the information because you think it has the potential to become evidence. Not all of it will. But keep it. One day, when you get more clues, you may be able to tie that other information in.


Information becomes evidence when it is used to make or help make a decision or conclusion. Thus all evidence is information, but not all information is evidence. Admittedly this is a little pedantic, and the two words are often used as synonyms. I often call all information evidence, and feel justified in doing so by thinking of all information as potential evidence just waiting for the right question to be asked!


Evidence is the use of information to support a conclusion. A piece of information may support 0, 1 or many conclusions; it should only be referred to as evidence when supporting a conclusion, otherwise it is only information.

So: If I have two sources which both contain information about the birth-date of my great-grandmother, and I am trying to work out when she was born, then both pieces of information are evidence. I may weight one piece of evidence higher than another when deciding which birth-date is more reliable, but I will explain why I did so in a note:

[Fictitious example]

"Cousin Charlie always said our grandmother Mavis celebrated her birthday on 1st April 1911, but her birth registration on 30th August 1911 by her father Alfred said she was born on 25th July 1911. Her father Alfred was recorded in the England and Wales census as being away from his family home on 2nd April 1911, and trade directories for the same period show him practicing his business as a photographer 200 miles away in July 2011 (where Mavis is recorded as born.) There is no obvious reason for Mavis's mother and siblings to celebrate the wrong birth-date, but the penalty for late registration of a birth may have caused Alfred to falsify the date and place when he registered it."

If there's a piece of information in your family record etc. that isn't relevant to a conclusion, then it's still information and not evidence. That doesn't mean you can ignore it if it doesn't fit with a conclusion you've reached; if it is relevant, it's evidence. However, your evidence might be my information if it isn't relevant to my interests.


Let me add a third category: data

  1. A collection of unsorted/uncorrelated records is data.
  2. Collated data that tells you something useful becomes information.
  3. Information with proof is evidence.

For example, in your example of "piles of ... records" (particularly the letters and emails) you have a lot of data, which on its own is probably largely useless, as much will be hearsay. However, you can consolidate and cross-reference, to confirm it... and that is then information with a use.

The historical records will, on their own, be evidence to support your information, which allows you to take an absolute position.

In genealogy we have to be careful about using uncorroborated data as fact... and in my own research I've been led down a few blind alleys by data given by close relatives, which turned out to be only partially true or totally untrue.

Family myths are common... many (most?) are just that: myths!


The first two answers are correct but there is a variation of 'evidence' that is worth mentioning.

We've just heard that information can be considered evidence in the context of some theory or conjecture, i.e. whether it supports it or contradicts it.

Some people consider any specific mention of a person to be evidence of a person existing with the associated details - usually with a particular name. These "evidence persons" are often referred to as personae. We implicitly combine these personae to create the normal "conclusion person" that most people will be acustomed to. However, it may be that one persona actually refers to a different person and may need to be changed. Some evangelists therefore give each persona its own ID and allow them to be manipulated separately.

The slight difference here is that a persona is evidence of the existence of some person from just one given source - not specifically for supporting/contradicting some theory. It's a subtle point but worth mentioning for the record.


Historical records which show where they are from, eg. a birth certificate with BDM South Australia on it, are regarded as evidence. Personally I scan original documents and attach the files to the people in my family tree software program. With the information you've gathered it's important to look for evidence which backs this up- certificates, newspaper articles, school records etc.

  • 2
    While I like the other two answers and how evidence and information is contrasted, I think it's important that you distinguished and identified concrete examples of evidence. In other words, something isn't evidence just because I think it is. :)
    – jmort253
    Oct 10, 2012 at 5:31
  • See the last sentence of your answer; it might not be clear that you distinguish between a "source" and the information contained in the source.
    – GeneJ
    Oct 17, 2012 at 17:21

The National Archives holds a lot of information in the form of passenger lists for ships arriving in Australia in the first half of the twentieth century. When I locate the one of those lists that contains the names of my grandmother and father, I have evidence for the time and place of their migration.

Exactly the same document constitutes evidence for different claims made by a hundred other family historians (who had ancestors on the same ship) and is irrelevant information for thousands of others (who did not).

Of course, If I were to undertake a study of the ethnic origin of migrants in the period 1919 to 1939, then the whole collection of passenger lists would constitute an important data source to be analysed.

Now if I locate an electoral roll showing my grandmother registered to vote before the ship arrived, then there is conflicting evidence (of the time of immigration or the identification of the relevant individual). To resolve the conflict, I would seek more information that might provide additional evidence.


Any source of information can be considered evidence, however, some evidence is false and some is true. Ideally we are always looking for multiple independently derived sources written by persons who have direct knowledge of the claims being made. Also ideally, you would not enter a claim into your database unless you had at least one source of evidence. You would of course also enter the source into your database and reference it by that claim. I also recommend categorizing all your sources. I have a number of articles on my blog concerning evidence and sources (http://gigatrees.appspot.com/blog/tag-sources.html). You might check out those covering defining source categories and evidence models and indicating impossible claims.

  • 2
    You misunderstand negative evidence, which is 'an inference we can draw from the absence of information that should exist under particular circumstances' to quote Elizabeth Shown Mills in "Evidence Explained". It is NOT false evidence.
    – user104
    Apr 16, 2017 at 15:08
  • 2
    Also on your blog on how to add negative evidence, you say 'The Genealogy Proof Standard refers to evidence that has been disproved or that is impossible as "negative" evidence.' But The BGC Genealogical Standards Manual (2000) which includes the GPS doesn't refer to negative evidence at all.
    – user104
    Apr 16, 2017 at 15:11
  • 'evidenceexplained.com/content/quicklesson-13-classes-evidence—direct-indirect-negative is a tutorial form the Evidence Explained website that explains negative evidence
    – user104
    Apr 16, 2017 at 16:23

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