Tuesday, March 03, 2009

Induction & Reference Classes in a Criminal Trial in Texas

In Schutz v. Texas, 957 S.W.2d 52 (Tex. Crim. App. 1997) accused was convicted of aggravated sexual assault on his six year old daughter. At his trial an expert for the prosecution was allowed to testify that the child's allegations were not the result of manipulation or fantasy. The Texas Court of Criminal Appeals (the state's highest appellate court in criminal cases) held that the expert's testimony was equivalent to prohibited testimony about the truthfulness of the child witness. The Court also said that "evidence that a person's allegations are the result of manipulation or fantasy is inadmissible. Such evidence never assists the jury because the jury is just as capable as the expert of drawing the conclusions involved." In note 10 of its opinion the Court of Criminal Appeals responded to a critique of this point by Judge Womack in his concurring opinion:
Judge Womack contends that our exclusion of expert conclusions concerning the truthfulness of allegations is illogical. He isolates three different types of statements that an expert might make: (1) children who are fantasizing or being manipulated behave in certain ways, (2) this child did not behave in those ways, and (3) this child was not fantasizing or being manipulated. He claims that (3) necessarily follows from (1) and (2), and, because we permit expert statements of the type (1) and (2) variety, we must necessarily permit conclusions of type (3). But, for his argument to work, Judge Womack must assume that the expert testifies that all children who are fantasizing or being manipulated behave in certain ways. If only some exhibit the behaviors in question then a conclusion that a particular child is not fantasizing or being manipulated because he does not exhibit the behaviors does not necessarily follow. But, given the imprecision of psychological science and the variability of human nature, no competent and honest expert could make the global statement necessary to satisfy Judge Womack's syllogism. At most, statements of type (1) and (2) would provide some inductive support for a conclusion of type (3). But an expert opinion of type (3) would also be supported by personal observations and lay knowledge of human behavior. The latter is clearly the exclusive province of the jury, and the former, along with statements of type (1) and (2) can be imparted to the jury by the expert. The jury can then make the inferences necessary to determine whether a type (3) conclusion is warranted without the expert commenting on that issue.
This is good legal food for philosophical thought.

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Sunday, March 01, 2009

Character Traits as Reference Classes

In United States v. Williams the Third Circuit Court of Appeals spoke of judgments about the probative value of character as "sweeping and non-individualized judgment[s]." In Commonwealth v. Adjutant the Supreme Judicial Court of Massachusetts saw a big difference between evidence such as the reputation of a person for violence and evidence that a person had attacked other people with boiling water, a butcher knife, and a crowbar.

I have some questions about "reputedly violent people" and "people who attack other people with crowbars etc."

Although reference classes are thought to be an ingredient or basis for statistical inference, can we nevertheless legitimately refer to "people who are reputedly violent" and "people who attack other people with crowbars" as "reference classes"?

What if you and I have never actually observed the behavior of a person who is reputedly violent or what if you and I have never observed the other behavior of a person who has attacked another person with a crowbar? Perhaps these are "reference classes" in the sense that they are culturally-inherited generalizations based on societal experience? Or are they instead or just as much "reference classes," or "generalizations," that people such as you and I extract from the other beliefs that you and I have about human behavior, human motivations, human derangement, etc.? If we extract such reference classes from our other beliefs, are we learning from or making use of experience? What if the beliefs from which we extract reference classes rest in part on experience?
What is the relationship between the putative reference classes (i) "people who are reputedly violent" and (ii) "people who attack another person with a crowbar"?
A. Is #(ii) a subset of #(i)?

B. Does #(ii) displace #(i)?

C. Even though #(ii) seems more specific, or more narrow, than #(i), does #(i) carry some information that #(ii) does not harbor?

  • Of course, there is the preliminary question whether #(i) harbors any information whatever about members of that reference class. I answer peremptorily: "yes." But by what epistemic right do I do so?
  • Questions ## A-C above were prompted by my recent reading of some material by James Franklin on reference classes. He thinks it's time to think further about reference classes. I agree.

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    coming soon: the law of evidence on Spindle Law