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 disproved.
    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 types.
    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 certainty."
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 physical.
    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 answer.
    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 that.
    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.