Types of Evidence Useful for Understanding the JFK Assassination
(December 2000)

   Understanding the JFK assassination depends on one’s ability to
extract the few valuable pieces of evidence from the large mass of
unhelpful evidence. This requires us to understand the various types
of evidence, how evidence is used in the legal system, and the ways in
which evidence may be used by students of the assassination. This
essay provides a brief introduction to the basic types of evidence and
their characteristics. It puts formal legal definitions into readable
English and extracts the most important ideas from them.
(Surprisingly, the law uses English poorly, and is full of vague terms
and words with multiple meanings. While this ambiguity may give
lawyers, judges, and the law the flexibility they consider important,
most of the time it only confuses the rest of us.)
   The legal system uses a wide variety of terms to describe
evidence, many of which deal with minor or specialized aspects of
evidence that are irrelevant to the assassination. Worse, a number of
terms overlap or duplicate one another. Different sources often offer
conflicting definitions. To the lay person, this can be very
confusing. Luckily, we as critical thinkers in the JFK case need only
concern ourselves with major distinctions.

Definitions and properties

What is evidence?
   Here are some typical legal definitions of evidence: (1) any
species of proof, or probative matter, legally presented at the trial
of an issue, by the act of the parties and through the medium of
witnesses, records, documents, exhibits, concrete objects, etc., for
the purpose of inducing belief in the minds of the court or jury as to
their contention; (2) testimony, writings, or material objects offered
in proof of an alleged fact or proposition; (3) that probative
material, legally received, by which the tribunal may be lawfully
persuaded of the truth or falsity of a fact in issue; (4) all the
means by which any alleged matter of fact, the truth of which is
submitted to investigation at judicial trial, is established or
   In other words, evidence includes all the ways by which we try to
prove allegations.

Ideas versus objects
   Evidence can be ideas or objects. Ideas, or human interpretation
of information relevant to the allegation in question, can be
delivered orally, or testified to, by a witness under oath, as
testimonial evidence. Testimonial evidence can also be given in
written form, via affidavits or depositions.
   Ideas from nonwitnesses can also be presented in written form,
generally as documents of various kinds. Such evidence is called
documentary evidence, which can be defined as ideas represented on
material objects such as deeds, wills, titles, letters, contracts,
receipts, X-ray plates, and so forth.
   Evidence can also be presented by means of objects, sometimes
collectively referred to as material objects, physical objects, or
"probative material." Such evidence is called demonstrative evidence
or real evidence. Demonstrative evidence is seen, heard, etc.,
directly rather than being described by a witness. By illustrating
some aspect of verbal testimony, it can help the jury understand the
crime. Demonstrative evidence does not directly address the question
of guilt, however. Examples of demonstrative or real evidence are
guns, contracts, maps, diagrams, photographs, models, charts, medical
illustrations, and X-rays.
   Thus, evidence can be said to encompass testimony, writings, and
physical objects.

Relation to the allegation
   Evidence is either direct or indirect. As its name suggests,
direct evidence relates immediately to the allegation being tested. If
the direct evidence is true, the allegation is established. Black’s
Law Dictionary defines direct evidence in these ways, among others:
"Evidence, which if believed, proves existence of fact in issue
without inference or presumption," and "Evidence…which in itself, if
true, conclusively establishes [a] fact." (As noted in "Using
important words precisely," fact should not be used in this way
because it refers to something not yet established.) An example of
direct evidence would be the surveillance video of a person robbing a
convenience store. Another piece of direct evidence would be a witness
who saw a person steal a car. Direct evidence in the JFK assassination
would be the testimony of a witness who saw someone fire one or more
shots from the Texas School Book Depository.
   In contrast, indirect (circumstantial) evidence does not bear
immediately on the allegation, but rather on something related to it.
From the related fact(s), the existence of the allegation in question
can be inferred (but not proved). Indirect evidence is normally the
strongest collectively, when multiple pieces combine to strengthen a
particular conclusion. Indirect evidence is sometimes called
collateral circumstances.
   At first glance, direct evidence would seem to be stronger than
indirect, because the former can prove the question whereas the latter
requires inference (deduction or induction). And yet, the opposite can
be true—circumstantial inference can be correct if its data are
correct and its patterns of reasoning are sound, whereas a conclusion
derived from direct evidence can be wrong if the evidence is flawed.
For these reasons, the law generally does not favor direct or indirect
evidence over the other. A judge or jury considers evidence of all
   Evidence that is indirect to the crime is direct to some facet of
the crime. For example, an audio tape of two conspirators planning a
crime is direct to the conspiracy but indirect to the crime itself
because it cannot prove that the conspirators actually committed the
crime. A receipt for purchasing a gun is direct evidence that a
certain person owned the gun but indirect that he used it in
committing a crime. The great majority of evidence considered in
typical trials is indirect to the crime itself.

Strength of evidence

   The law uses two archaic terms for strength of evidence, neither
of which are helpful for the assassination. The stronger type is
called mathematical. According to Black, evidence is mathematical if
it "establishes its conclusions with absolute necessity and
   Moral evidence is "highly probable" or "highly persuasive," i.e.,
weaker. Examples include arguments from analogy or induction,
experience of the ordinary course of nature or the sequence of events,
and the testimony of men. (Sorry, you women—this last phrase comes
directly from the law.)
   But what about evidence that is weaker than "highly probable" or
"highly persuasive"? The law seems to have no consistent terms for
this category. For the purposes of the JFK assassination, we may
describe the three common strengths of evidence as conclusive (or
strong), persuasive, and weak (or something similar). These would
correspond to probabilities of roughly 95% and greater, 75–95%, and
less than 75%.

Reliability of evidence

   One of the most important characteristics of evidence is its
reliability. This property is particularly germane to understanding
the JFK assassination, where much questionable evidence has been
produced and intermingled with the solid evidence. Unfortunately, the
law provides no systematic way other than the courtroom to distinguish
good evidence from bad. Fortunately, however, disciplines outside the
law do.
   Determining the reliability of a piece of evidence is a two-step
process. The first step, often neglected but exceedingly helpful, is
to assess the testability of the evidence. If the evidence cannot be
tested rigorously and objectively, it is useless because we can never
know whether it is right or wrong. While this sounds like a truism, it
is actually an enlightening principle that when used consistently can
bring order to large masses of evidence. The second step is to
determine the correctness, or accuracy, of the evidence. Thus to
determine the reliability of evidence, we first decide whether it can
be meaningfully tested, and then, if the answer is positive, we try to
validate it.


   Many ideas or pieces of evidence are inherently untestable, that
is, they are of a type whose correctness cannot be determined
objectively. The eminent philosopher of science Sir Karl Popper has
discussed at length this property of evidence, which he calls
falsifiability. (See his essay "Science, pseudo-science, and
falsifiability.") Most people feel intuitively that "testable
evidence" is something like "scientific" data, in distinction to
untestable evidence, which would come from "unscientific" sources. The
precise definition is quite straightforward, however: testable
evidence is that which has a concrete object (which can be a photo, a
graph, a table of data, etc.) and a description or interpretation of
the meaning of that object written by a person capable of
understanding it. (In a courtroom, the person would be a sworn
witness, often an expert.) The physical nature of the object allows
the statement to be checked independently and objectively by others
(i.e., to be falsified). This opportunity for validation forms the
core of the first step in determining reliability.
   For simplicity, then, let us define testability as the property of
being objectively falsifiable, or simply physical. Any evidence that
is not testable is automatically weak, i.e., it has little or no
probative value. For example, evidence based on someone’s word is
untestable and therefore unreliable and weak. But since testabililty
is only the first step toward reliability, testable evidence is not
automatically reliable.

Examples of testable evidence

   Testable evidence includes everything physical. For the JFK
assassination this means medical (e.g., X-rays and autopsy
photographs), classical ballistics (e.g. tracing bullets and casings
to weapons by matching lines and markings), applying physics to
ballistics (as in the Z-film), wound ballistics (e.g. using shapes,
sizes, and markings of wounds to determine whether of entrance or
exit; determining direction of bullets from beveling and coning), hair
and fiber analysis, fingerprints, chemical analysis (emission
spectrography, NAA, and other modern techniques), and the more-modern
DNA analysis. Note that every one of these types of evidence combines
a physical object with an expert’s interpretation of it. The next few
paragraphs give some brief examples of each of these in the JFK case.

   Ballistic analysis. By comparing the markings on the three largest
fragments of bullets found in the limousine and at Parkland Hospital
with various rifles, FBI investigators were able to determine that
they had all been fired from Oswald's rifle to the exclusion of all
other rifles. Similar results were found for the three cartridge cases
found on the sixth floor of the Depository.
   Wound-ballistic analysis. The physicians who examined the bullet
wounds to Kennedy and Connally tried to categorize them as entrance or
exit wounds from their properties. They got most of them right. The
team at Parkland misidentified the tiny hole in the throat as an
entrance wound, however. They were right that it looked like an
entrance wound, although it was really the exit wound from the body
shot that entered Kennedy's upper back/lower neck region. The Parkland
personnel were handicapped because (a) they did not know of the back
wound, and (b) they soon destroyed the wound by using it as a starting
point for their tracheotomy.
   Chemical analysis. The set of lead fragments from the bullets was
analyzed twice for trace elements, once by the FBI in 1964 and later
by the HSCA in 1977. When properly interpreted, both sets of results
offer very strong evidence (but not proof) that only two bullets, both
from a Mannlicher-Carcano rifle, hit Kennedy and Connally. When
combined with the ballistic evidence for the large fragments, they
show that the Mannlicher-Carcano in question was in fact Lee Harvey
Oswald's. Thus, all the fragments recovered that were big enough to
analyze came from two bullets fired from his rifle that day.
   Analysis of motions by physics. The motions of Kennedy's head and
body after the fatal bullet hit his head are recorded on the Zapruder
film. When analyzed carefully in terms of conservation of momentum and
energy, the number of bullets hitting his head and their general
direction of origin can be determined nearly conclusively.
   Forensic pathology. The documentary records from JFK's autopsy
include notes, reports, diagrams, photographs, and X-rays. All are
available for qualified physicians to study and interpret.
   Hair and fiber analysis. The Warren Report describes how, for
example, the fibers caught on Oswald's rifle were compared with those
of the shirt he was wearing that day.
   Fingerprint analysis. The Dallas Police Department and the FBI
lifted various fingerprints and palmprints from the rifle, the boxes
on the sixth floor of the TSBD, and so on. Some were Oswald's; some
remained unidentified.
   Analysis of documents. The Warren Report describes how various
documents from Oswald's possession were checked for accuracy. Some
were found to be fakes, such as his ID cards. Others were found to
contain alias signatures in his handwriting, such as the records of
ordering and receiving his pistol and his rifle.

   Once a piece of physical evidence has been identified, it still
must be tested before it may be considered reliable. There are various
ways to test evidence. One is to examine whether it agrees with other
evidence that has already been validated. Another is to examine the
consequences (predictions) of the evidence and see whether they
correspond to reality. A third is to gather new data to test the piece
of evidence. This also can be a long job, but it is truly worth the
effort. (For an organized series of steps for checking evidence, see
"A critical method for the JFK assassination" in the essay "A critical
method for understanding the JFK assassination.")

Examples of untestable evidence
   Numerous as the examples of testable evidence listed above are,
their numbers are dwarfed by the huge mass of evidence that is
untestable. (See "Shadings of eyewitness testimony.") These types of
weak evidence includes testimony of eyewitnesses at the scene (a vast
record indeed); some undeterminable fraction of Marina Oswald's
testimony; recollections of the medical personnel who attended Kennedy
in the emergency room at Parkland Hospital (much discussed of late);
recollections of the staff at Parkland Hospital; recollections of the
ambulance personnel; recollections of the autopsy technicians in
Bethesda Memorial Naval Hospital; deathbed confessions concerning who
might have ordered Kennedy killed; speculations about who else might
have wanted him killed and why; views stated by members of the Kennedy
family and others close to the assassination; reports of seeing Oswald
in various places (Clinton, LA?) or with various people (with Ruby and
the Carousel Club; having an office at 544 Camp Street in New Orleans;
meeting with "Maurice Bishop"; test-driving a car in Dallas; etc.);
entire books written by people confessing to be conspirators or in
league with the actual conspirators (such as Robert Morrow's
"Betrayal"); and so on. You get the picture. Many books about the
assassination have been based virtually completely on this weak
evidence. Consequently, they must all be dismissed outright as
unverifiable, therefore uncertain, and therefore useless in practice.

Purging the unreliable evidence

   Welcome to the frustrating world of the JFK assassination! What do
we do when we can't trust most of the evidence? We follow steps 3a,b
of the pattern of critical thinking offered in "A critical method for
understanding the JFK assassination." First we divide the available
evidence into strong and weak, where strong effectively means
physical. Then we eliminate all the weak evidence and proceed with the
   Step 3 is perhaps the most distinctive of the nine steps in this
pattern of critical thinking. It is controversial among JFK
researchers because it goes against the grain of so much of their
research. And yet it is fully justified from the standpoints of logic,
common sense, and tradition. It offers the fastest and most efficient
path to delimiting the answer. It offers the most realistic assessment
of the quality and quantity of the available evidence. It offers an
immediate sense of how close to an answer we are likely to get. (See
the essay on asking the right first question.) Anyone who does not
follow this method is going against logic, common sense, and centuries
of critical tradition, and is guaranteeing an uncertain, if not wrong,
answer. Seen in this light, there is no choice.
   Of course, clearing out bad data will significantly restrict the
number of conclusions we will be able to draw. It will also restrict
the number of topics we will be able to consider. Many JFK researchers
consider this penalty too harsh to bear. I say the opposite—I consider
it a relief to have settled this all-important question. The last
thing I want is to be wrong about any part of the assassination. Far
better to remain silent about some part than to be wrong about it.
   It is very important to be conservative here—better to err on the
side of eliminating some data that are correct than to let in any data
that are wrong. The moment we include any data of dubious reliability,
we can no longer be sure that any subsequent conclusions are correct.
Our goal needs to be much like the physician's "First, do no harm." I
see no way to avoid these harsh measures if we really want to get the
   But this approach is really nothing new—we do the same in all
matters of importance in our daily lives. When we go looking for a new
car, for example, we want to be sure that we are provided with the
correct information. If a salesman misleads us or offers incorrect
information, we go somewhere else immediately. When we set out to buy
a house, we often get it inspected so that we know the truth about it.
Why then should we be any less rigorous with the JFK assassination?
   Surprisingly few JFK researchers treat their evidence like this.
They let in anything and everything, and hope that somehow the weaker
information will be sorted out in the wash. Even if they give initial
lip service to hard evidence, they don't follow it in practice. They
just take it all in and arbitrarily emphasize what seems best to them.
Those practices guarantee disaster. The link between evidence and
conclusions cannot be beaten—include unreliable evidence and your
conclusions will be unreliable. I submit that no one among us wants
   Then why do JFK researchers insist on including unreliable data?
It clearly is an irrational act. We had best leave this question until
later in the course, for the answers are not pretty.