The Great Mix-Up: Sources, Information, Evidence, and Proof


Image: Bart Luyckx, “Magnifying glass and reflection” via Flickr Commons

Sources. Information. Evidence. Proof. For many genealogists, these four terms can be baffling. They are often transposed, merged, miscommunicated, or all of the above. Let’s dissect all four and look at them in practice with the case study “Jethro Potter’s Secret: Confusion to Conclusion in Indiana, Illinois, Ohio, and Michigan,” written by Harold Henderson, CG(SM) and published in the June 2013 issue of the National Genealogical Society Quarterly (NGSQ).

Every genealogist consults sources. They are the pension files we comb through at an archive, the gravestones we find in a cemetery, the census returns we browse through on the web, and the books we read in the library. Sources are not the courthouses, libraries, websites, or other repositories that we visit. They are the papers or books we physically hold, the tombstones we read with our eyes, and the digitized records we save to our computers.

Sources are divided into three major categories: original sources, derivative sources, and authored works. Original sources are first recordings of some type of action or event. In Henderson’s case study, Mary Masterson’s deposition, which was taken in 1924 and tucked away into a pension file (see page 112), is an original source. It has not been rewritten, abstracted, or transcribed, and it is still in its original form in the pension file. Derivative sources are versions of original sources that were created at some later date. A transcription of Mary’s deposition that was created by a genealogist in 1973 would be a derivative source.

Sources don’t shift from original to derivative. If Mary’s deposition disappears from the pension file, a transcription made in 1973 would still be a derivative source. If the pension file in its entirety were digitized or microfilmed, the newly created images would still be considered original. Authored works are a different animal—they are written bodies of work based upon information from a variety of sources. Henderson’s case study is an authored work.

What do sources give us? Information—about people, places, and events. As genealogists, we seek the information items that sources provide—names, dates, and occupations, to name a few. In Henderson’s case study, Mary Masterson’s deposition (the source) tells us that she lived with a man named Jacob for eight months and had a child with him (the information).

Information comes in three forms—primary, secondary, and unknown—based on who gave the information. Primary information has a higher probability of being accurate because it is provided by someone with first hand knowledge of the event. Secondary information, on the other hand, generally has a lower probability of being accurate, since it is hearsay. The information provided in Mary Masterson’s deposition is primary information. Mary recalled events she personally experienced.

The informant—or the person who provided the information—is the key in determining whether information is primary or secondary. Did the informant experience the event, or did they hear about it later? Sometimes the identity of the informant or their personal experience regarding the event is not known. In these instances, it is impossible to determine whether information is primary or secondary, so it is considered unknown.

Henderson’s case study also includes a deposition by Hattie Gerwig, the sister of Mary Masterson (see page 112). According to Hattie, Mary gave birth to a child whose father was Jacob McCroskey, the husband of Mary’s paternal aunt, Minerva. However, the author points out that Hattie was too young to remember these events herself—so the information provided in her deposition is secondary information.

Now it gets complicated: evidence! Evidence—whether direct, indirect, or negative—does not exist until a research question is asked. In Henderson’s case study, the question is “Who were the parents of Jethro Potter?”

We transform information into evidence as we interpret and analyze it in the context of our research question. Direct evidence is a single piece of information that directly answers the question. Indirect evidence is information that does not directly answer the research question, but that can be combined with other clues to provide the answer. Negative evidence is the absence of information that in itself suggests the answer to a research question.

In Henderson’s case study, direct evidence provides one possible answer to part of the research question: Jethro Potter was the son of Noadiah Potter. However, Mary Masterson and Hattie Gerwig’s depositions each provide indirect evidence that Jacob McCroskey was Jethro’s father. This evidence is considered indirect because the depositions do not specifically name Mary’s child as Jethro—they simply provide information that she gave birth to a son in the late 1860s. The indirect evidence from the depositions must be considered along with other evidence—for example, Jethro’s approximate birth date—to suggest an answer the research question. As with all NGSQ case studies, a body of this evidence is presented in the article as part of the process for establishing proof.

What is proof? A conclusion is proven (or considered accepted) when it satisfies the five elements of the Genealogical Proof Standard (GPS): a reasonably exhaustive search into a variety of sources, complete and accurate source citations, careful analysis and correlation, resolution of conflicting evidence, and a sound, written conclusion.

Henderson’s case study meets the GPS. He has researched and documented dozens of different sources relevant to the location and time period—vital records, social security records, census enumerations, numerous record types found in pension and estate files, court records, newspaper obituaries and articles, deeds, county histories, tombstone markers, oral interview notes, and funeral home records. The information provided by these sources provides both direct and indirect evidence to answer the research question: “Who were the parents of Jethro Potter?” The evidence is correlated and explained to address conflicts. Finally, the author’s conclusions are presented in a sound and coherent written manner.

The more familiar we are with these four key elements—sources, information, evidence, and proof—the stronger our questions, research, analysis, and conclusions will be. There’s no better way to reinforce these concepts than to find one or more recent NGSQ case studies and analyze them:

  • What is the genealogical question being asked?
  • Do you find any derivative sources among those used in the case study? If so, why do you think these were used as opposed to original sources?
  • Are you able to find an instance where the author draws secondary information from a source? Does it prove to be reliable?
  • Can you find direct, indirect, and negative evidence in the case study?
  • Was conflicting evidence presented? Has it been discussed and resolved as part of the effort to establish proof?
  • Did the author present a clear and convincing argument?

When we have a genealogical question, we consult a variety of sources. It only makes sense that, as genealogists, we would also study numerous examples of complex proof arguments as we work to establish proof from our own research. The highest level of genealogical scholarship can be found in NGSQ case studies. Take advantage of these resources available to you as an NGS member. Practice your skills—read, analyze, and repeat.

Click here to log in to the NGSQ Archive and read Harold Henderson’s article.


  1. March 16, 2015 5:29 pm
    • March 17, 2015 12:22 pm

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