Case Building 101 for Historical Researchers


Researcher Bev Wright has a legal background. Now that she’s pursuing history, she wonders how the practices of one field applies to the other:

“I have a great deal of experience in building evidence in a court of law,” Bev writes. “Some circumstantial facts and evidence, laid one on top of another, often lead to fairly irrefutable conclusions. If before a jury, we call that evidence. When can we say with fair certainty that we may not be able to prove with documentary evidence a particular fact or set of facts? Setting all our facts out—lining them up—is it alright to say that there are not any or many other conclusions that may be drawn, aside from this particular one? Does that scenario fit the GPS?”

The short answer, Bev, is “Oh, yes!” Now for the long answer. …

Bev’s question actually involves two different issues:

  • The "GPS" that Bev invoked.
  • The nature of evidence as used by historical researchers.

The Genealogical Proof Standard is discussed at EE 1.5. To meet this standard of proof, a conclusion about identity or kinship has to meet 5 criteria:

  1. Reasonably exhaustive research (RER) using best sources available;
  2. Thorough identification of sources that support each assertion;
  3. Thoughtful correlation and analysis of findings;
  4. Resolution of any conflicting evidence; and
  5. A written proof argument or proof summary that identifies all the evidence and lays out reasoning.

No. 5 is perzactly what Bev describes doing for a court of law. So, yes, the bottom line is the same in both the legal and genealogical fields. We must find sufficient evidence, analyze it skillfully, and build a case for only one reasonable conclusion.


This is a point at which genealogists deviate from legal practices. Genealogists are actually more precise in the terms they use.(1) Different terms identify different types of evidence. In brief:

  • Direct evidence gives us an explicit answer to our question. It may be right or it may be wrong. Either way, it gives an answer to the question we're asking. We then have to marshal enough other pieces of evidence from elsewhere to prove whether that direct evidence is right or wrong. In short, even with direct evidence, we still have to “build a case” for our conclusion.
  • Indirect evidence is information that is relevant to our problem but does not give us an explicit answer. Instead, we combine it with indirect evidence, and reasoning, to “build a case” in the manner Bev describes. We can even use it to disprove direct evidence. More often we use it because our thorough research turned up no direct evidence. In fact, this happens very, very often.

Bev asks: “When can we say with fair certainty” that we need to build a case?

The short answer is: Every time we make an assertion, because even direct evidence can be wrong.

The long answer lies in Criteria 1 of the GPS—that “reasonably exhaustive research" (RER) that calls for using

  • the full range of records known to exist for the time and place (not just those that are convenient); and
  • every known, appropriate, research strategy.

If we fall short on the first requirement, then every unconsulted record is a ticking time bomb that could explode our claim. If we haven’t applied the second requirement, then we’ve likely missed a lot of evidence that could have been used and might change our conclusion.

If we’ve met the GPS’s Criteria 1 and we still don’t have a document that provides direct evidence, then we may still be able to build our case with nothing but indirect evidence. Usually this takes one of two tacks: 

  • If we’ve been very thorough with our research, we’ve likely turned up many pieces of indirect evidence that—all together—point to one logical conclusion.
  • If we have any conflicting evidence then, Criteria 4 of the GPS requires us to resolve the conflict before we can say the case is built. In fact, Criteria 4 calls for us to play Devil’s Advocate with our evidence, trying to disprove our hypothesis just as thoroughly as we try to prove it, to make sure that no conflicts exist.

Eventually, if we’ve been thorough in our correlation and analysis, then we will have solid reasoning to support our argument that all this “circumstantial evidence” (as the legal field calls it) adds up to only one logical conclusion.

1. The “Evidence Analysis Process Map” discussed in yesterday’s QuickTips (“The Four Cornerstones of Genealogy,” 6 July 2018) provides a graphic outline of how genealogists classify sources, information, and evidence.

2. For more guidance on case-building, see Elizabeth Shown Mills, “Building a Case When No Record ‘Proves’ a Point,” Ancestry 16 (March-April 1998): 26–31; archived at Google Books, (

HOW TO CITE: Elizabeth Shown Mills, "Case-building 101 for Historical Researchers," blog post, QuickTips: The Blog @ Evidence Explained ( : posted 7 July 2018).