A Common and Exasperating Fallacy about Eyewitness Identifications

"Inaccurate eyewitness identifications are involved in (80%, 90%, pick your percentage poison) of wrongful convictions. This demonstrates that eyewitness identification evidence is very unreliable and that it is the primary cause of wrongful convictions."


I have protested against this kind of reasoning before. See, e.g., this post and this post. But my protests haven't stopped people -- defense lawyers, newspaper reporters, judges, and even academics -- from making this kind of argument. I find this extremely exasperating.
It may be true that eyewitness identifications are frequently or very frequently inaccurate. But the sort of statistic quoted above does not show (A) that they are such (i.e., frequently or very frequently inaccurate), or (B) even if they are frequently inaccurate, that inaccurate eyewitness identifications are the primary cause of wrongful convictions of innocent people.
Why not?
1. It is not enough to know the number of cases in which eyewitness identifications are inaccurate. It is necessary (but not sufficient) to know the number of cases in which eyewitness identifications are accurate. If eyewitness identifications are accurate far more often than they are inaccurate, the discovery that a "large" number of eyewitness identifications are inaccurate does not demonstrate that eyewitness identifications are frequently or very frequently inaccurate.
2. The fact (if it is a fact) that incorrect eyewitness identifications were "involved" in wrongful conviction of innocent people in a high percentage of cases does not demonstrate that inaccurate eyewitness identifications are the primary cause of wrongful conviction of the innocent.

• I'll bet that courtrooms and judges and jurors and defense counsel and oxygen were "involved" in the vast majority of the cases in which defendants were tried and wrongfully convicted of a crime. It doesn't follow that either courtrooms, judges, jurors, or oxygen molecules are the primary cause of wrongful convictions of innocent defendants. For example, it would be useful -- and probably essential -- to know how often other inaccurate evidence of guilt -- evidence other than eyewitness identifications -- was used in trials that ended with the conviction of the innocent and how much the use of such other evidence accounted for the wrongful convictions that have been observed.

• It is often said, almost in the same breath, that inaccurate eyewitness identifications and false confessions are each involved in, say, 80% [or some other such number] of wrongful convictions of innocent people. Does it follow that (A) the primary cause of wrongful conviction of the innocent is inaccurate eyewitness identifications and (B) the primary cause of wrongful conviction of the innocent is false confessions? No: the two propositions are inconsistent.

Of course, it is possible that (B) eyewitness identifications are very frequently inaccurate and that (C) they are the primary cause of wrongful convictions of innocent people. But the statistic that (A) "inaccurate eyewitness identifications are involved in X% of cases in which innocent people have been shown to be innocent" doesn't get you from A either to B or to C.

&&& The dynamic evidence page

Evidence marshaling software MarshalPlan

Curiosity

I hope I will never again hear some politician ask,

"Why space travel?"

 

Just answer:

"Curiosity!"

    &&&   The dynamic evidence page

Evidence marshaling software MarshalPlan

Experimental statistical evidence about eyewitness identification, intersecting reference classes, and trial by jury

On a list today I said the following on the topic of "experimental statistical evidence about eyewitness identification, intersecting reference classes, and trial by jury":
The problem [XXX] points to is [an example of] the familiar problem of intersecting reference classes -- which occurs in this context because every eyewitness and every eyewitness situation are (at least) always "slightly" different and there will always be some features about an eyewitness or an eyewitness situation whose significance or non-significance [has] not been empirically tested.

Does this mean that generalizations about [] eyewitnesses and eyewitness situations are irrelevant, or useless? No, not necessarily. What it means is that until better evidence comes along, "subjective human judgment" must determine whether this or that empirically-untested feature matters. This is the way it always is - there will always be such features - even though we fans of the rule of law and rational inference feel uncomfortable about this inevitable situation. Perhaps this problem (of the inevitable presence of empirically untested features) is one very good reason for trial by jury [of 12 or more persons].

&&&
The dynamic evidence page
Evidence marshaling software MarshalPlan

The Myth of the Myth of Memory as Tape Recorder

Over and over memory researchers (e.g., Elizabeth Loftus) and proponents of reforms of the legal treatment of eyewitness evidence assert that the mind or the brain is not like a tape recorder or a camera -- and newspapers and TV reporters are fond of repeating such pronouncements. These memory researchers and legal reformers mean to debunk, they say (over and over) the popular misconception that the brain is like a tape recorder. I have been puzzled about such anti-memory-as-tape-recorder pronouncements. How many members of the public actually believe that human memory is nearly perfect because the human organism and its brain and its sensory organs etc. work like a perfectly well-oiled and well-calibrated machine? How many serious scholars said anything like that? I have done a bit of Google research. My conclusion: IT IS AN URBAN MYTH THAT MEMBERS OF THE PUBLIC OR SCHOLARS SUCH AS PSYCHOLOGISTS GENERALLY BELIEVE OR EVER GENERALLY BELIEVED THAT THE HUMAN ANIMAL AND ITS PERCEPTIONS AND ITS MEMORY WORK LIKE AN ALMOST PERFECT TAPE RECORDER OR CAMERA.  (I may eventually marshal and present some of my evidence here, but, frankly, I'm not sure I need to.) Did Proust subscribe to this memory-as-camera memory-as-perfect-machine myth? Shakespeare? Immanuel Kant? Jung? Hegel? Helmholtz? John Dewey? Are members of the public unaware that they sometimes or often forget where they put their keys or their children, or that they often cannot remember the names of some or many of their high school classmates? Is it really the case that jurors need to be told that the human mind, sense organs, etc. do not operate like (well-maintained and perfectly-calibrated) tape recorders or cameras?

• I suppose that an occasional person believes or believed that the human animal's perceptions are machine-like, always accurate, and permanent even for practical purposes. So what? Some people probably believe that the moon is made of green cheese and that they died yesterday. It doesn't follow that many or most people believe such things.

Fuzzy Logic, 1965

   &&&
The dynamic evidence page
Evidence marshaling software MarshalPlan

July 2012 NJ Jury Instructions on Eyewitness Evidence

&&&

The dynamic evidence page

Evidence marshaling software MarshalPlan