Alhassanain(p) Network for Heritage and Islamic Thought

Credibility Attributes: Tangible Evidence

Authenticity. Common experience with tangible evidence reveals concern about its authenticity, reliability, and accuracy. As I noted in explaining tangible evidence in Figure 1, we have first to consider whether this tangible item is what it is represented to be or what we believe it to be. The issue of authenticity often brings to mind the possibility of efforts on the part of others to mislead us in various ways. Documents can be forged, photographs can be altered, and objects can be contrived or misrepresented in various ways as I illustrated in Section 4.1.3 in my example concerning Bullet III in the Sacco and Vanzetti case. A more recent example involves a document that caused no little embarrassment to our [then] Secretary of State, Colin Powell. At a United Nations hearing he presented evidence drawn from a document represented as being an agreement between Saddam Hussein and persons in the country of Niger concerning the purchase by Saddam of certain nuclear materials. This document was later shown to be a rather clumsy forgery.

The trouble is that we often need no other person or group to mislead us; we can easily mislead ourselves. I know of one instance that occurred years ago that led to an incorrect inference that was based on a very high quality intelligence photograph. This photo was simply mislabelled about the time it was taken. We thought it was taken two days ago, when in fact it was taken about two weeks ago. The blood test you experienced last week produced a serious result that surprised both you and your physician. You take the test over again and no such surprising result occured. A short time later the testing service apologized for the lack of authenticity of your first test. Someone had mislabelled the test results of another person as belonging to you. A mistake was made but you would probably not believe the person who mislabelled your blood specimen tried to mislead you in any way.

Apart from the fields of intelligence analysis, law and medicine, historians are obviously concerned about authenticity questions. As Lichtman and French tell us, some forgeries were viewed as authentic for many years until they were carefully examined[115]. The examples they mention include the documents concerning the Donation of Constantine and the Protocols of the Elders of Zion. Inauthentic objects include the Viking rune stones found in Minnesota. The authors emphasize a fact well known in law, namely that it often requires considerable technical skill and highly specialized knowledge to uncover a forgery. Evidence of fabrication, and the degree of similarity between the artifact or document and other items of the period are examined carefully. So is the chain of custody through which the item has passed. In law, great attention is now paid to establishing the chain of custody through which some tangible item, to be presented at trial, has passed. Each stage through which an item passes offers opportunities for the intentional or unintentional alteration of or substitution for  some original item. Sadly, such concern about chain of custody was not so evident in 1921 when Sacco and Vanzetti were tried and convicted.

Reliability. The termreliability requires special attention. The reason is that this term is so often applied, as a synonym forcredibility , with reference to human sources and the testimony they provide. I believe this to be a mistake. What is at issue regarding the testimony of human sources is the extent to which we canbelieve what they tell us.  Believability or credibility is a much more complex matter as I will now begin to explain and to which I will return when examining the attributes of testimonial evidence.

Reliable processes are dependable, repeatable, or consistent. In engineering, for example, reliability concerns the probability that some system will continue to function for some specified time in the future. In the behavioural sciences the reliability of some test concerns the likeliness that it gives the same, or nearly the same, result on successive occasions. As we know, there are various statistical indices of the extent to which some result may be expected to occur in repeated samples of the same process.

One reason why reliability becomes a concern regarding tangible evidence is that so many tangible items open to our direct inspection are products of various devices. Examples include photographs and other sensor images such as radar and infra-red, voice recordings, and the traces of physical processes recorded by instruments of various kinds. The issue here concerns the reliability or dependability of the process or device used to make the tangible recording of the process of interest. One matter of interest here concerns the stated reliability of the device in question: How often would you get the same result if you took another reading? Another matter of interest concerns how well the device was maintained. As an example, the prosecutor at your trial on a charge of speeding produces a tangible record that was produced by the arresting police officer's radar gun. This record shows that you were travelling at 75 miles per hour, where the posted speed limit on part of the M-5, where you were travelling, was 60 MPH. You deny that you were exceeding this speed limit. Fortunately for you, your attorney produces evidence that the radar guns used by the police in the area in which you were arrested have a poor record of service. In addition, your attorney offers the testimony of a person who recently serviced the radar gun used in your arrest. This person testifies that this radar gun was damaged and looked like it had been dropped on several occasions.

Accuracy.   Another attribute of many items of tangible evidence concern their accuracy. Sensing devices that produce images of some sort vary in the degree of their sensitivity or resolving power. We may not be entirely sure that it was person X in the image captured by the surveillance camera at the bank where the robbery occurred. The tangible document you are examining may contain errors and omissions. Perhaps this document was translated into English from another language. You would of course be concerned about the accuracy of this translation. Tabled entries of measurements of various sorts may contain errors. We are all made aware of various ways in which charts or graphs of statistical data can be misleading A common device used to enhance truly small observed differences is to plot these small differences on an expanded scale.

I come finally to an accuracy issue involving tangible objects. This issue concerns your own detection and recognition accuracy. You examine some tangible object and believe that it reveals an event E that is of interest in the inference task at hand. But a colleague, perhaps having better detection and recognition capabilities than you possess, argues that this object does not reveal the occurrence of event E. This example illustrates how it is often necessary to rely on the opinion of other persons whose experience and skills allow them to provide advice regarding all three of the attributes of the credibility of the tangible evidence you are examining.

Competence and Credibility Attributes: Testimonial Evidence

I come now to matters I have found to be the most interesting and difficult of any I have encountered in my studies of evidence. As I noted in Section 3.1 concerning the emergence of the concept of evidence, a problem was addressed in the very earliest studies of probability and evidence in the 1600s; this problem was called thecredibility-testimony problem . I also noted that I found discussion of this problem among probabilists to be more entertaining than useful. The major reason was that I could think of attributes of the credibility or believability of human sources of evidence that these studies did not address. I began my own studies of the credibility of testimonial evidence in the late 1960s. I had already formed the belief that credibility, as a credential of testimonial evidence, has several attributes. So, my question was: how many attributes influence the inferential force of evidence? My studies of this question took me into several fields including law, epistemology, and sensory psychophysics, as well as the common experiences we all have with the testimony given by others. Fortunately, these four areas of thought converge in suggesting the three attributes of the credibility of testimonial evidence that I have already mentioned several times:veracity ,objectivity , andobservational sensitivity [including the conditions of observation]. But my studies in law convinced me of the importance of another characteristic of human sources of testimony, namely thecompetence of the person providing testimony.

Before I begin my account of where these attributes of competence and credibility come from, I will again be concerned about how the matters I mention can appropriately be termed necessary ingredients in a science of evidence. In the process, I will make use of Carnap's comparative and quantitative concepts in all of science. First, studies of the attributes of the credibility of testimony allow us to make several important comparisons. They allow us to compare the relative credibility of different persons who may provide testimony in a given situation. Second, they allow us to compare the credibility of testimonial and tangible forms of evidence we receive. We might ordinarily believe that tangible evidence, things we can observe for ourselves, are naturally more credible than testimony we receive from other persons. That this belief is not always justified becomes apparent in our studies of credibility. This comparison seems quite important in contrasting credibility issues in various areas of science and in other areas that I will now illustrate.

In most areas of the physical sciences the greatest reliance is placed on tangible evidence in the form of recorded observations that are made as a result of repeated trials involving some observable phenomenon. The researcher explains with care the reasons why these observations were made and how the results of these observations were obtained. Critics questioning these announced results can make their own observations under the same described conditions to satisfy themselves if they care to do so. But in the social and behavioural sciences and in various areas of the humanities, equally great reliance is placed on testimonial evidence obtained in some, but not all, situations that are replicable. I will return to a comparison of the forms of evidence obtainable in various areas later in Section 5.0 when I consider the benefits to all of us obtained by systematic studies in a science of evidence.

There are ways of grading the credibility of a source of testimonial evidence in quantitative terms. As I will illustrate later in Section 4.2.3, numerical assessments of the credibility of evidence arise naturally in numerical assessments of the inferential force of evidence. These credibility assessments can be combined in various ways with other numerical assessments concerning the strength of the linkages in a relevance argument that relates the event reported in testimony to some probandum or matter to be proved. In short, the strength of all the links in the chain of reasoning shown in Figure 3 can be expressed numerically in probabilistic terms. Appropriate combinations of these assessments can produce assessments of the inferential force of evidence that grounds the chain of reasoning. As I will continue to emphasize, my present purpose is simply to show how such quantitative assessments of the inferential force of evidence are possible. Whether they are employed or not depends on the interests of the person drawing conclusions from the evidence of interest to this person. In short, a science of evidence does in fact include methods for quantitative assessments of the credibility and the force of evidence.

Competence Attributes. I have already briefly mentioned two attributes of the competence of sources of testimonial evidence in Section 4.1 in connection with my description of the classification of evidence in Figure 1. In my studies of the manner in which testimonial evidence is assessed in our legal system I began to learn how the competence and credibility of a source of testimony are entirely different characteristics. I first observed this distinction in a note attached to the definition of competence given in Black's Law Dictionary. This notes says[116]:

Competency differs from credibility. The former is a question which arises before considering the evidence given by the witness; the latter concerns the degree of credit to be given to his  story. The former denotes the personal qualification of the witness; the latter his veracity. A witness may be competent and yet give incredible testimony…competency is for the court, credibility is for the jury.

I will add other attributes besides veracity as far as the witness's credibility is concerned. I also noted that the distinction between competence and credibility is not always appreciated in other areas as it is in law; intelligence analysis is one such area I know of. In news reports, as well as in intelligence documents I have read, I have seen numerous statements such as the following: "We can believe what X told us because he had good access". This is an open invitation to inferential miscarriage. Competence does not entail credibility, nor does credibility entail competence.

In times past persons having various characteristics would automatically be ruled incompetent. Members of certain religious groups, including atheists of course, convicted felons, and even in some times members of certain racial groups as well as the spouses of a defendant were ruled incompetent. There are no such rules today as expressed in the Federal Rule of Evidence FRE 601 which says: "Every person is competent to be a witness except as otherwise provided in these rules"[117].

But FRE 602 requires that ordinary or lay witnesses must have "personal knowledge" of the event(s)  about which he/she testifies. This is an important rule to which I will refer again shortly in my account of attributes the credibility of testimony. We will have to sort out what it means to say that a witness has "personal knowledge"; this is where interesting epistemological issues arise. Briefly, what FRE 602 says is that we must have evidence to support the witness's actually observing the event to which he/she testifies, or had access to the information in his/her testimony. Though this rule is frequently cited as relating to credibility I have always thought that it forms perhaps the most important attribute of competence, If the witness did not make a relevant observation or did not otherwise have access to the information in his/her intended testimony, this surely goes against his/her competence.

Another attribute of competence is frequently cited. The witness must have the mental ability to understand what he/she observed so that this person is capable of providing an intelligible and coherent account of what he/she observed. So I have labelledaccess andunderstanding as the two major attributes of the competence of testimonial evidence. But I note that these attributes apply to ordinary or lay witnesses. But expert witnesses will appear in many contexts besides law. The opinion evidence they provide, which I noted in discussing the classification in Figure 1,  involves a variety of matters discussed in FREs 702 - 706. There is also a rule concerning opinion evidence provided by ordinary witnesses; it is FRE 701. I will have more to say about opinion evidence in my discussion of credibility that follows.

Credibility Attributes.

I began consulting works on evidence in law in about 1970. The very first topic of interest to me was what evidence scholarship had to say about credibility-testimony problems. Over the next few years I consulted dozens of treatises on evidence law and found a wealth of interesting information of great value in the probabilistic work I was doing. Of particular interest to me was the experience, accumulated over many centuries in our Anglo-American judicial system, of forming questions regarding the impeachment or support of the credibility of witnesses. In Section 3.1 I mentioned how concern about the credibility of external witnesses began to emerge around 1500. Study of these questions became very important to me as I began to think about what are the major attributes of the credibility of persons who provide testimonial evidence. I will return to these questions in a moment.

At the time, I also had interests in the area of signal detection theory [SDT] and its applications in sensory psychophysics. In SDT studies human subjects are given series of trials on which visual or auditory signals at various low levels are presented and always against a background of noise. One objective in such studies was to determine theabsolute thresholds of our sensory systems, i.e., the lowest level of signal intensity that we can reliably detect. The use of SDT in such studies is interesting because this theory was not generated by psychologists, it was borrowed from the field of electrical engineering[118]. In such studies the subjects report Y = I heard it [or I saw it], or N = I did not hear [see] it; there was only noise. What separated SDT studies of thresholds from previous studies in psychology was that on a certain percentage of trials no signal, but only noise [N], would be presented. This allowed the researcher to determinehit rates [h] andfalse-positive rates [f] defined as follows:

h = P(Y|S + N), the probability that the subject says she/he heard [saw] it, given that           the signal was present [S], and f = P(Y|N), the probability that the subject says she/he heard [saw] it, given no signal but only noise [N].

Plots of h and f on what is calleda receiver operating characteristic curve [ROC]         are very revealing because for the first time researchers were able to separate out measures of our observational sensitivity from a variety of other factors, such as our expectancies and our desires, that influence a person's willingness to response Y or N.  Work on SDT studies also influenced my work on the credibility of witnesses who provide testimonial evidence as I will explain. I wrote several early papers exploring this connection[119].

But I was finally able to identify and name the major attributes of the credibility of testimony when I began to examine works in the area of epistemology concerning what is meant by the wordknowledge . Recall my example in which we wish to know whether or not event E occurred and you say we should ask person P, she will know whether E occurred. So, we ask P and she says E*, that E did occur. The question is how do we tell whether or not P knows that E occurred? In epistemology there exists what is termed thestandard analysis of knowledge, which is traceable to Plato'sTheaetetus [120]. On this analysis,knowledge is justified true belief . In the case of person P, we say on this analysis that Pknows that event E occurred if: (i) E did occur, (ii) P was justified in believing that E occurred [i.e. that P got good evidence that E occurred] , and (iii) P believed the evidence she obtained.

This standard analysis of knowledge seemed to make perfect sense to me [as a non-epistemologist]. But, as I read further about this analysis, I encountered great debate about its merits. I began to read about paradoxes associated with the standard account of knowledge that were so often linked to the works of Gettier[121]and Radford[122]. So I began to see what the trouble with the standard analysis was all about. In another place I have recorded my own reaction to the wide array of examples and counterexamples of paradoxes associated with the standard analysis[123]. The more I read the more I encountered imaginative but hardly convincing examples of paradoxes. But I also began to read comments from philosophers concerning their reactions to this imaginative but unconvincing dialogue. Nozick said he became so mired in counterexamples and increasingly complicated conditions for knowledge that he finally stopped reading the literature[124]. Cohen said that discussion of these paradoxes had led many epistemologists into "an imaginary world of freaks, speculation, and science fiction"[125].

I found no account of the requisites for knowledge that is free of controversy, So I decided explore the consequences of the standard analysis to see where it would lead me in my interests in attributes of the credibility attributes of testimonial evidence.  But I had one additional concern about where this analysis would lead me. This standard analysis concern whether our source P "knows" whether event E occurred of not. She tells us that event E occurred in her testimony E*. The question then is: Do we also "know" that event E occurred, just because P tells us that it did? Consider the uncertainties we face in answering this question. First, we do not know ourselves whether E occurred; we were not privy to the situation in which event E occurred or not. This is why we are asking P, who we believe to be competent. Further, we do not know how good was the sensory evidence that P obtained. Nor do we know about the actual extent to which P believed her sensory evidence regarding E, if she took this sensory information into account at all. Finally, we do not know if P is reporting in accordance with what she believes about event  E. Figure 4 below is an account of the standard analysis regarding P's knowledge of event E [Part A] and how this influences our uncertainties [Part B] ; here is where the three testimonial credibility attributes arise.

Figure 4A shows the sequence of events in accordance with the standard analysis. Event E did happen, P received good evidence for E [or "non-defective evidence" as some epistemologists say], whereupon P believes the evidence she obtained. But we know none of this; all we have is P's testimony E* that event E occurred. You should note that the chain of reasoning shown in Figure 4B is a decomposition of the credibility foundation stage shown in Figure 3 when we have testimonial evidence. As Figure 4B shows, we have three inferences to make from P's testimony E* according to this theory of testimonial credibility stemming from the standard analysis; each stage of this inference defines an attribute of the credibility of a source of testimony. How is this theory to be tested? I offer four tests; the first comes fromeveryday experiences we all have with persons who report on things they observe.

Experience 1 . People do not always believe what they tell us.  This is related to the person'sveracity . We could not say that this person was being untruthful if this person believed what she/he told us. In our example, the first question we ask is: Does P really believe that E occurred, as she reported to us?

Experience 2 . People do not always base their beliefs on the evidence of their senses. On occasion, we are all known to base our beliefs about the occurrence or non-occurrence of events not on what our senses report but simply because we either expect or wish certain events to occur or not occur. This is a matter of a source'sobjectivity . An objective observer is one who bases a belief on evidence rather than upon expectations/surmise or upon desires. In our example, the next question we ask concerning our source P is: If P does believe what she reported to us, upon what was her belief based? Did she believe what her senses told her about event E, or did she believe E occurred because she either expected or wanted it to occur?

Experience 3 . Our senses are not infallible. We all make mistakes in our observations. Sometimes mistakes are due to the conditions under which our observations are made, or to our own physical condition at the time of our observation. So, the final attribute I have termedobservational sensitivity [including the conditions of observation]. If the source based a belief on good sensory evidence, this would allow us to infer that the reported event did occur. So the final question is: How good were P's relevant senses at the time of her observation, and what were the conditions under which she made this observation?

But these three questions we ask about the attributes of P's credibility must be answered by ancillary evidence we have bearing upon her veracity, objectivity, and observation sensitivity. What questions should we ask about these three attributes? Answers come from the centuries-old experience in the field of law and constitute my second test of the theory of testimonial credibility I have described. In searching over fifty treatises on evidence in the field of law I found 24 questions that are asked at various times concerning attempts to undermine or support the credibility of a witness. You can find a listing of these 24 questions in other works I have written or have been a part of writing[126]. What I found especially interesting was the all 24 of these credibility-related questions can be sorted out into the three attributes: veracity, objectivity, and observational sensitivity [including the conditions of observation]. Sixteen of these questions can be sorted into exactly one of the these attributes; four can bear on either of two of these attributes; and three can bear upon all three of these attributes. In short, I found no credibility-related questions regarding testimonial evidence that could not be sorted into one or the other of these three attributes.

My third test involves the "personal knowledge" requirement for ordinary witnesses that I mentioned above concerning our FRE 602. These Federal Rules of Evidence did not exist in Wigmore's day, but there has always been concern about what is meant by "personal knowledge". The basic problem was well expressed by Wigmore[127]:

It is obviously impossible to speak with accuracy of a witness' "knowledge" as that which the principles of testimony requires. If the law received as absolute knowledge what he had to offer, then only one witness would be needed on any one matter; for the fact asserted would be demonstrated.

When a thing isknown (by a tribunal or other decider) to be, itis ; and that would be the end of inquiry.

As Wigmore understood, courts and juries can never "know" whether or not a witness  "knows" that the event she/he reports did occur. Wigmore interpreted the "personal knowledge" requirement to mean[128]:

The witness made a personal observation,

The witness formed an inference or a belief based on this observation, and

There was adequate observational or sensory data upon which to base this inference.

I have no knowledge about whether Wigmore ever read about the standard analysis of knowledge in epistemology. But his interpretation of personal knowledge seems like it could have been drawn from this analysis that forms the basis for my account of the attributes of testimonial credibility.

My final test of the use of the standard analysis of knowledge comes from SDT. As I noted, this theory allows the separate analysis of observational sensitivity from what I have termed objectivity factors such as a person's desires and expectations in forming beliefs based on observations. But veracity issues rarely, if ever, enter into analyses of SDT studies. The reason is that the subjects in SDT studies have no motive to be untruthful in saying whether they observed a signal or just noise. Instances in which plots of false positives exceed hits are very rarely encountered and researchers usually interpret such cases as a subject's misunderstanding instructions or simple lapses of attention.

I have three final comments to make about the three attributes of credibility of testimony identified above. The first is that second hand testimony based on other testimony involves catenations of the three stages of reasoning described in Figure 4B. The result is that we have the veracity, objectivity and observational sensitivity of each human source in a hearsay chain to consider as I have discussed in detail elsewhere[129]. In the case of opinion evidence given by a person, I have also described inferential elements other than testimonial credibility that we encounter in evaluating opinion evidence[130].

Finally, if you are wondering whether I regard the chain of reasoning for testimonial evidence given in Figure 4B as being final in any sense, my answer isno . I mentioned how any chain of reasoning could be decomposed to reveal additional sources of doubt. This applies to chains of reasoning I construct as well as to those anyone else constructs. Here is an example. Suppose you examine my chain of reasoning in Figure 4B and consider the first link involving the human source's veracity. You say: "I agree that veracity of a source of testimony depends on whether this source is telling us something that she believes to have happened. But what beliefs are you considering, her beliefs while she is now telling you, or the beliefs she had a month ago when she made the observation she says she made? Human beliefs are supple or elastic. What she believes now, and what she believed at the time of her observation might not be the same".

In reply to your entirely reasonable question, I say that I have already considered such instances and can easily see how one's beliefs while giving testimony may be different from this person's beliefs at some earlier time when an observation was made[131]. There are many reasons why these beliefs at different times might be different. Lapses in memory supply one reason, but so does that fact that many events have been interposed between an earlier belief and one presently held. The person may simply have changed her/his belief about what was observed. One form of evidence concerning a changed belief involves what are termedprior inconsistent statements . Did this person ever tell someone else a different story than he/she is now telling us? This is one instance of an evidential test that can involve either veracity or objectivity as I have explained.

4.2.3 The Inferential Force, Weight or Strength of Evidence

Considering this final credential of evidence certainly brings Carnap's quantitative concept in science to the fore. Probability and, thus, mathematics now definitely enters our discussion of a science of evidence. You now have an item of information that you are calling evidence because you have established its relevance in the inference at hand, and you have assessed its credibility. The question you now ask is: How strongly does this evidence favour or disfavour propositions or hypotheses you are considering? I mentioned earlier that in all views known to me the force of evidence is graded in probabilistic terms. An interesting consequence is that we presently have different formal or mathematical systems of probabilistic reasoning; in each of these systems there are different views about what the force, weight or strength of evidence means. Each of these formal systems says interesting and important things about the force of evidence, but no one view says it all. I recall Jonathan Cohen once remarking that apples are measured in different ways at the market. They are sold by number, by weight, or by volume and each makes perfect sense in certain situations. As I will mention, the same is true regarding the force, weight or strength of evidence.

In my account of the emergence of the concept of evidence, I mentioned Locke's idea of thedegrees of assent provided by evidence as we draw conclusions from it[132].  A bit later, David Hume offered a comment that has always interested me. He said[133]:

Thus all probabilistic reasoning is nothing but a species of sensation… When I am convinc'd of any principle, 'tis only an idea which strikes more strongly upon me. When I give the preference to one set of arguments above another, I do nothing but decide from my feeling concerning the superiority of their influence.

In all contexts known to me conclusions reached from evidence are necessarily probabilistic. I can think of five major reasons. Our evidence is always incomplete, commonly inconclusive, often ambiguous, dissonant to some degree, and that comes to us from sources having any gradation of credibility shy of perfection. So, in assessing the inferential force of evidence, these are things we must keep in mind. No single probabilistic view of the force of evidence that I know about accounts for all five of these considerations equally well. I have a general comment to make about the essential ingredients of the force of evidence before I consider four quite different views about how it should be assessed and graded.

Consider the general argument structure shown in Figure 3. In this simple situation depicted in the figure for a single item of evidence, I have shown a chain of reasoning consisting of credibility and relevance links. The force of evidence E* on proposition or hypothesis H depends on the strength of each link in his chain of reasoning. But you can now observe difficulties we face when we have multiple items of evidence each linked to proposition H by often lengthy and possibly interconnected chains of reasoning. Earlier, I used the current metaphor of "connecting the dots" to illustrate problems we face in assessing the overall force of masses of evidence. Figure 3 illustrates how we encounter different forms of "dots". Some dots, such as E*, represent details in our evidence. Other dots represent ideas we have about the meaning of these evidential dots and come in the form of the probanda to  which these evidential dots are connected to matters we are trying to prove or disprove. The point is that assessing the force of individual items of evidence is difficult enough, but when we have masses of evidence to contend with the task becomes astonishingly difficult, as Wigmore recognized many years ago.

It is not my intention to summarize the mathematical details of each of the four probability systems I now discuss as they concern the force, weight or strength of evidence. In the first place I have done so elsewhere[134]. In the second place, these details may be uninteresting, even perhaps unintelligible or unimportant, to many readers whom I have such great interest in reaching in my present comments about a science of evidence and why they should have an interest in it. The approach I will take is exactly the approach taken by Anderson, Twining and me in our recent work written essentially for law students. From experience, one way to quickly induce sleep among law students is to write an equation on the board. Fortunately, the essential elements of these alternative views can be expressed in words and in pictures as we have done in our work for law students[135]. The four views of the inferential force, weight or strength of evidence are as follows.