Evidence Revisited: DNA, POE, and GPS
From OnBoard - Newsletter of the BCG
Helen F.M. Leary, "Evidence Revisited:
DNA, POE, and GPS," OnBoard 4
Science and the law are in agreement: there is only one
way to prove kinships beyond reasonable doubt DNA
testing. As a genealogical standard, that is hardly practical.
For at least the past 25 years, genealogists have tried
to use another standard for judging the persuasiveness of
evidence: the preponderance of the evidence popularly
called the POE. In practice, the results have been troublesome.
During the summer of 1997, trustees of the Board for Certification
voted to discontinue use of the term. They based that decision
upon several factors discussed below.
PROBLEM WITH THE POE
The term preponderance of the evidence was borrowed
from the legal field, where it is the standard used by judges
and juries to decide the liability of a defendant in civil
lawsuits. Prior to the advent of DNA testing, it was also
the standard by which paternity was proved in court. One
legal encyclopedia for laymen restricts it to a "case
of contested facts" and defines it as "superiority
in weight (determined by value and not by amount) of the
evidence presented by one side over that of the other."1
The legal standard has always been recognized as inexact
when applied to genealogical compilations a fact
that has always been acknowledged by the Board, by those
who lecture under its auspices, and by leading speakers
and writers. It is inexact for two reasons:
- The legal standard requires that evidence be weighty
enough to only tip the scales one way or the other. In
genealogy, the standard is stricter a statement
is considered "proved" when the evidence supporting
it is of sufficient power to convince a reasonable, unbiased
person. This does not mean "beyond the shadow of
a doubt," the strict standard used in criminal cases.2 The genealogical standard is now and always has been between
the two legal extremes.
- The genealogical standard applies when evidence is direct
and virtually impregnable (e.g., an an interlocking series
of birth, marriage, and death certificates, for example).
It applies when circumstantial evidence is assembledto
distinguish among several persons of the same name, perhaps.
And it applies when evidence is insufficient for a solid
case, because records do not survive or were never created.
Although the genealogical use of POE has been beneficial
in some ways directing thought and discussion towards
the nature of genealogical proof it has often been
misunderstood. Some believed it to be a method for deciding
what kind of information to collect, a means of judging
its probable reliability, or an arbitrary yardstick to measure
"how much evidence" constitutes "proof."
Even the leading genealogists have disagreed, over the
years, as to the term's precise meaning although
they do agree on the standard itself. Further, with the
advent of televised court cases and interminable "expert"
discussions of the latest Trial of the Century, legal terminology
has been bandied about to the confusion of all.
Clearly, the term preponderance of the evidence has outlived its usefulness. In abandoning the term, however,
the Board has not abandoned the standard nor has
the Board revised it, watered it down, or made it stricter.
Perhaps it is time we called our standard by its own name:
the genealogical proof standard GPS, if we
must have an acronym.
In any event, both genealogical standards and Board requirements
call for an understanding of information, evidence,
INFORMATION AND EVIDENCE
DNA testing has been effectively applied in rare genealogical-historical
cases e.g., to prove that Anna Anderson a.k.a"
Anastasia" was not the Russian princess of that name.
DNA testing, however, is not available for general useexhuming
the bodies of all known John Smiths until an ancestral match
is made is impractical, to say the least.
Because we cannot be absolutely certain of genealogical
facts without the aid of DNA tests, the statements we make
are assertions of what we believe to be true. If we do not
safeguard the validity of our assertions, we may spend time
and energy creating a hybrid grafting somebody else's
ancestry onto our family tree. Therefore, we base every
genealogical statement on evidence.
Evidence is drawn from information in written records,
oral testimony, and artifacts. Information is inert
and impartial, until we use it to support an assertion about
someone's identity, relationship, biographical event, or
circumstance. As an example, let us say: according to the
1850 census, John M. owned real estate worth $25,900. That
information is neutral it conveys no more than exactly
what it says. When we interpret the information and assert
that "John M. was a wealthy landowner," we have
drawn a conclusion. That conclusion is the sum of prior
deductions based on our judgment that (a) the census data
is reasonably reliable; and (b) $25,900 represents realty
of higher-than-normal value.3 By resting our statement on
hitherto neutral information, we convert the data into evidence.
We measure the power of evidence its convincing
weight by asking of it the following questions:
- Are these sources generally accepted as reliable? Is
the information itself coherent and free of obvious error?
There are, of course, no "irrefutable" sources.
Even a birth certificate may be mistaken in some of its
- Was the data's significance understood? Were its logical,
physiological, psychological, social, legal, religious,
ethnic, and historical contexts accurately reflected in
the evidentiary conclusion?
- Is the data being used as direct or indirect (circumstantial) evidence? This judgment depends on how
it is used. "John M. was a wealthy landowner"
rests on direct evidence taken from the census. The same
evidence is indirect when used to support a complex statement
about John's identity e.g., "the land value
points to his being the plantation-owning John, not the
Baptist minister John."
We use these standards for negative assertions, also. "John
M., who died in 1842, was not the father of Henry M., born
in 1847" sounds incontrovertible but nevertheless fails
if evidence about John's death or Henry's birth is in error.
Proof is dependent on the sum of our evidence. No single
item, regardless of how reliable, well-interpreted, or direct,
can stand alone in support of an assertion about a specific
We cannot rest a statement such as "our ancestor John
M. was a wealthy landowner" on 1850 census evidence,
for it does not speak to John's identity as "our ancestor."
The sum of the evidence might include the presence in his
household of Henry M., aged four but it must also
include at least two other things:
- an evidentiary chain that links this child with the
Henry M. who later fathered a child Marmaduke, who fathered
a child Henry, and so on until the chain connects to us.
- supporting evidence that the householder, John M., was
indeed Henry's father, for the enumerator in that year
recorded no direct information about relationships.
Whatever the content of a genealogical statement, when
we correlate and assemble a body of evidence in its support,
we build a case for its validity.
Judgment about a proof's power to convince depends on answers
to another set of questions:
- Was the search for relevant information thorough? Did
it include all sources that a reasonably knowledgeable
genealogist would expect of a competent search?
- Is the evidence valid? (We return to the evaluation
described above to answer this question.)
- Was the evidence assembled correctly? Does all the
underlying data concern the same person, event, or relationship?
Has it been faithfully portrayed, without distortion or
- Does the proof satisfactorily answer questions raised
by (a) data that conflicts with the genealogical statement;
and/or (b) information that might have been available
in records that were never created or have been subsequently
If the answers to these questions warrant our conviction
that the statement is substantially true, it is said to
be proved. That does not mean that it can never be disproved
by additional data or more precise interpretation. It does
mean that frivolous challenges, such as "but something
else could have happened" or "The History of the
M. Family (undocumented) says otherwise," should not
be viewed as sufficiently powerful to destroy our case.
A lineage, pedigree, or genealogy is a series of related
assertions proved by a complex web of interwoven evidence.4 In weaving that web, we cite our sources and, when necessary
for clarity, explain our evidence. We may have inadvertently
chosen faulty materials or made a mistaken connection, but
our goal is a portrait of the family that is as close to
the true picture as possible.
Helen F.M. Leary, CG, CGL
1. You and the Law (Pleasantville, N.Y.: Reader's
Digest, 1984), 790.
2. Technical terms for the standard used to convict in
a criminal trial are clear and convincing evidence in some jurisdictions and beyond a reasonable doubt in others. Although the names themselves do not connote
a restrictive standard, jury instructions normally expound
on them, emphasizing the serious nature of a decision that
may lead to defendant's loss of liberty or life.
3. To make this conclusion, we would have to compare John
M.'s property value with that of a reasonably broad cross-section
of other landowners in the same area and time period.
4. The Board defines genealogy as a written account of
the descendants of a given person or couple. Some call this
kind of compilation a descendancy.
This article was originally published in OnBoard,
BCG's educational newsletter and is protected by copyright.
Individuals may download and print copies for their personal
study. Educators are granted permission to provide copies
to their students as long as BCG, OnBoard, and the
appropriate author are credited as the source of the material.
Republication elsewhere is not permitted.