A critical method for validating physical evidence
17 October 2002

    The great strength of physical evidence is that it can be evaluated objectively and repeatedly. This makes it possible, at least in principle, to establish its meaning beyond reasonable question, something that cannot be said of witness evidence. Getting to the meaning is a two-step process, however, with the first step being "validating" the evidence, or determining whether it is genuine. Given the recent claims that much of the physical evidence in the JFK assassination has been tampered with or faked entirely, up to and including the Zapruder film, it seems important to establish a systematic procedure for validating such evidence. I believe that there exists such a process, a variant of the critical method of thinking that is discussed on its own page here. This method of validation is classical in nature, in that it follows the highest logical and scientific precepts. There is nothing new in it other than the way it is expressed.
    The method follows the critical method nearly step by step. Like that method, it is empirical, objective, progressive, parsimonious, provisional, and self-correcting. Here are its steps, followed by a brief discussion and a series of actual examples of its use in the JFK assassination.

1. Ask the question. (Is this piece of physical evidence genuine?)
2. List all possible preconceived answers, no matter how bizarre or biased. (The three general possibilities are "genuine," "tampered with," and "planted.")
3. Assemble all relevant evidence.
4. Divide the evidence into "strong" and "weak," where "strong" means objectively validated (physical evidence that has passed the process described here), and "weak" means of a type that cannot be objectively validated (all witness evidence, plus any physical evidence that has not yet been validated).

    Strong evidence only

5. List all possible answers consistent with the strong evidence.
6. Choose the simplest answer consistent with all the strong evidence. (The simplest answer is usually "genuine.")
7. Test this working hypothesis against its consequences (predictions) or against new evidence that arises.
8. Consider the working hypothesis proved if it passes all the tests and no other answer is possible. (Uncommon.) Then go to step 12.
9. Retain the working hypothesis if it passes all the tests but other answers are possible. Then go to step 12.
10. Reject the working hypothesis if it fails one or more of the tests. Choose the next-simplest answer and return to step 7 for testing.
11. Continue until you find the simplest hypothesis that survives all the tests. (If two or more successful hypotheses are equally simple, retain them as multiple working hypotheses.) Then go to step 12.

    Strong and weak evidence (Steps 12 through 19 are only for cases where you wish or need to add weak evidence to the mix. If you stay with strong evidence only, proceed to step 20.)

12. Add selected weak evidence to the strong evidence. Remember that this will downgrade any answer to "speculative and without logical force."
13. List all possible answers consistent with the strong and weak evidence.
14. Choose the simplest answer consistent with all the evidence.
15. Test this working hypothesis against its consequences (predictions) or against new evidence that arises.
16. Consider the working hypothesis proved if it passes all the tests and no other answer is possible. Go to step 20.
17. Retain the working hypothesis if it passes all the tests but other answers are possible. Go to step 20.
18. Reject the working hypothesis if it fails one or more of the tests. Choose the next-simplest answer and return to step 15 for testing.
19. Continue until you find the simplest hypothesis that survives all the tests. (If two or more successful hypotheses are equally simple, retain them as multiple working hypotheses.) Go to step 20.

    Either set of evidence

20. Continue testing the successful hypothesis (or hypotheses) against new evidence as it appears. Status of answer: reliable if from strong evidence only, speculative and unreliable if from strong and weak evidence.

Discussion
    Just as in the case of interpreting evidence, there is little or no reason to add weak evidence to the mix when there is abundant strong evidence, for weak evidence cannot in and of itself make strong evidence stronger. In fact, it does the opposite—it weakens it. The only legitimate reason to turn to weak evidence is insufficient strong evidence. The weak evidence can be used as a source of new leads, one of which may eventually pan out. But this is nearly a random process, since you have no way of telling from the weak evidence itself whether it is correct—you have to check it out first, which can be an exhausting process. You only turn to weak evidence when you have no other way to go.

Examples
    This 20-step process may seem forbidding at first, but it is not really. A few examples will show how it is actually used, and that no one need fear it. For simplicity, we restrict the initial examples to strong evidence.

    CE 399
    Question: Is CE 399 genuine?
    Possible answers: genuine; tampered with; planted.
    Strong evidence: ballistically matches Oswald's rifle (fired from it); chemically paired with wrist fragment from Connally (i.e., fired from that rifle that day); consistent with the injuries to Kennedy and Connally; strong chain of custody.
    Possible answers consistent with the strong evidence: genuine; tampered with after the fact.
    Simplest of these answers: genuine.
    Comments: Since the "genuine" answer is the simplest that works, we must begin with it ("retain" it). We are not justified in invoking anything more complex without direct evidence for it. Since it is "retained" but not "proven," we must test it further.
    Additional tests: Does the idea that CE 399 was fired from Oswald's rifle that day fit with other strong evidence? Yes, the other two large fragments that also were traceable to Oswald's rifle, the nature of the back wound, the forward bending of fibers in Kennedy's jacket and shirt, and the three empty shells from the same rifle that were found on the sixth floor, to name a few. Does the idea conflict with any strong evidence? No.
    Final status of the "genuine" answer: Retained and strengthened.

    Wrist fragment
    Question: Is the lead fragment from Connally's wrist genuine?
    Possible answers: Genuine; substituted after the fact, presumably by someone with access to FBI storage facilities..
    Strong evidence: chemically linked to CE 399 by NAA; tight chain of custody.
    Possible answers consistent with the strong evidence: genuine; substituted.
    Simplest of these answers: genuine.
    Comments: Same as for CE 399. Since the "genuine" answer is the simplest that works, we must begin with it ("retain" it). We are not justified in invoking anything more complex without direct evidence for it. Since it is "retained" but not "proven," we must test it further.
    Additional tests: Does the "genuine" answer fit with other strong evidence? Yes, the pattern of wounds through Connally's body that culminated in the bullet being buried in his left thigh. Does the answer conflict with any strong evidence. No.
    Final status of the "genuine" answer: Retained and strengthened.