Law courts are important institutional settings in which public understanding of science is problematic. Courts have struggled with the question of how to handle scientific evidence in a system of justice in which lay jurors are responsible for deciding the facts of the case. Judicial conceptions of science and of jurors' capacities to understand scientific evidence inform decisions in particular cases. Such decisions, in turn, act as precedents that, for better or worse, embed judicial conceptions of public understanding of science into the workings of the legal system. This paper examines an English case in which the difference between “scientific” and “common sense” evidence was explicitly at stake. In this case Regina v. Adams, DNA evidence was used to convict the defendant of rape. The principal item of prosecutorial evidence was a match between DNA profiles developed from the defendant's blood and from semen recovered at the crime scene. Prosecution experts expressed the evidence in probabilistic terms, estimating a probability of one in 200 million that a DNA profile from a randomly chosen unrelated man in the relevant population would match the profile developed from the crime stain. Other so-called “common sense” evidence supported the defendant's not guilty plea. The case was appealed twice in the mid-1990s as the Court of Appeal deliberated over an innovative effort by the defense to counteract the prosecution evidence by converting the non-DNA “common sense” evidence into probability estimates. In its decisions, the Court reinstated a boundary between the “scientific” and “common sense” evidence, arguing that this boundary was necessary to preserve the jury's role as trier of fact. The paper's discussion of the court's boundary work addresses unresolved problems with the place of probability estimates in jury trials.
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References
1.
and Ronald Thwaites Q.C. and Marc Brittain, “Perfected Grounds of Appeal & Skeletal Argument,”Denis John Adams v. Regina, in The Court of Appeal, Criminal Division, 25 September 1997. Ruth McNally attended the second appeal, and McNally and Lynch interviewed Peter Donnelly (24 November 1997), an expert witness for the defense, and Ian Evett (18 December 1998), an expert for the prosecution.
2.
The judicial summary stated that the attack came from behind, and the victim only saw her assailant briefly. Donnelly (interview 24 November 1997, p. 12), provided a different version of witness's testimony, and stated that the day after the rape the victim told the police that she had a good view of her attacker and was confident that she would be able to recognize him again. In fact, according to Donnelly, she did claim to see him walking down the street a couple of years later, but the police were unable to locate the man at the time.
3.
and Kathleen Jordan, Sociological Investigations into the Mainstreaming of the Polymerase Chain Reaction (Ph.D. Dissertation. Department of Sociology, Boston University, 1997).
4.
This focus on a particular case is inspired by Harold Garfinkel's idea of “perspicuous settings”: specific occasions, cases, or practices that explicate fundamental concepts, themes, and distinctions that social theorists tend to address abstractly, often in endless debates with one another. The idea is to find a setting and embed a study in that setting, in order to explicate a relevant concept, theme, or distinction (in this case, the science/commonsense distinction). Our reliance on textual reconstruction, and our limited legal backgrounds, greatly limits the extent to which this study is “embedded,” in the way that Garfinkel recommends, in the case and its legal circumstances. See Harold Garfinkel, Ethnomethodology's Program: Working Out Durkheim's Aphorism (Lanham, MD: Rowman & Littlefield, 2002), 181-184.
5.
J. L. Austin devised the category of “performative utterance” to describe linguistic expressions that, when uttered in the appropriate circumstances institute or accomplish real-worldly events. J L. Austin, How to do Things with Words (Oxford: Clarendon, 1962). So, for example, under the appropriate ceremonial conditions, an official can christen a ship or pronounce a couple to be married. Such declarations do not describe preexistent conditions; instead, they perform, or contribute to the performance of, the state of affairs in question.
6.
Thomas Gieryn , Cultural Boundaries of Science: Credibility on the Line (Chicago: University of Chicago Press, 1999). Unlike the philosophers who have attempted to formulate principled demarcation criteria, Gieryn recommends a social-historical orientation to efforts by scientific associations and courts to accord or deny scientific status to candidate fields such as phrenology, creation science, and various social sciences.
7.
As an anonymous reviewer of an earlier draft of this paper noted, judges, attorneys, and expert witnesses are in a different situation from that of a jury. Unlike jurors, judges and attorneys often encounter repeated presentations of similar types of evidence and repeated performances by the same expert witnesses. Witnesses, attorneys, and judges thus have an opportunity to learn from prior cases and to adjust their actions accordingly. It is not necessarily the case, however, that judges have superior understanding of technical issues than jurors. See Gary Edmond and David Mercer, “Scientific literacy and the jury: reconsidering jury `competence',”Public Understanding of Science6 (1997): 329-357.
8.
For a similar suggestion made in an experimental study of probabilistic formulations of DNA evidence, see F. Taroni and C. Aitken, “Probabilistic reasoning in the law: part 1: assessment of probabilities and explanation of the value of DNA evidence,”Science & Justice38, no. 3 (1998): 165-177.
9.
The New York Times (2 March 2001, A-1, 17) reported that in the past 40 years, jury trials ending with verdicts in the United States had dropped from 5.4 to 1.5 percent of civil cases and from 10 to less than 5 percent of criminal trials.
10.
John Henry Wigmore famously stated that the presentation and testing of evidence in the trial court is “the greatest legal engine ever invented for the discovery of truth,” in Wigmore's Code of the Rules of Evidence in Trials of Law, 3rd ed. (Boston: Little Brown, 1940), 29.
11.
For a more elaborate description of DNA profiling techniques oriented to lay readers, see National Research Council, The Evaluation of Forensic DNA Evidence (Washington D.C.: National Academy Press, 1996). In the mid-1990s, the STR system began to replace the SLP technique, and the latter is rarely used anymore. However, because SLP was the key profiling technique used in Adams, it remains the focus of our discussion.
12.
and Saul Halfon, “Collecting, testing and convincing: DNA experts in the courts,”Social Studies of Science28, nos. 5/6 (1998): 801-828.
13.
and Jennifer Mnookin, “Fingerprint evidence in an age of DNA profiling.” The relationship between DNA profiling and fingerprinting is the subject of current research by Michael Lynch and Simon Cole.
14.
In 1994, the Home Office announced an initiative to construct a national DNA profile database. This national database uses the STR system. The first profiles were entered in April 1995.
15.
For a description of the database, see J. E. Allard, “Series sexual crimes identified by a DNA computerised database,”Advances in Forensic Haemogenetics, 4 (1992): 295-297.
16.
Examples include patient reports of experiences that psychiatrists attribute to hallucinations and contrary testimony about the speed of a particular automobile by defendant and arresting officer in traffic court. Paul Drew examines testimony at a rape case in which the victim and defendant give different versions of the circumstances leading to the alleged crime. See Paul Drew, “Contested evidence in courtroom cross-examination: the case of a trial of rape,” in Talk at Work: Interaction in Institutional Settings, eds. John Heritage and Paul Drew (Cambridge: Cambridge University Press, 1992), 470-520.
17.
As a reviewer of an earlier draft noted, the defense also relied upon expert evidence (viz., the testimony of Peter Donnelly). The Appeal Court tended to draw a sharp distinction between expert and commonsense evidence, independently of Donnelly's role as an expert. Donnelly presented himself as an expert who assisted the defense with a critique of the prosecution's “expert” evidence and who offered to represent the “common sense” evidence with a Bayesian procedure.
18.
Judgment, 1st appeal, p. 9 (page numbers are to a computer aided transcript by Smith Bernal, London).
19.
We did not have direct access to the two trials, and so our reconstruction is limited by the partial and retrospective summaries, citations, and quoted portions of transcript provided by the Court of Appeal.
20.
Quotations of witness statements by Dr. Harris, Ms. Lygo, and Mr. Lambert were taken from the document Thwaites and Brittain, (cit. no. 1), p. 2, sec. 3.1.
21.
Ibid.
22.
The reason that four probes would result in seven bands is that three of the probes identified heterozygous sites in the particular samples (two each for three probes) and one identified a homozygous site.
23.
Thwaites and Brittain, (cit. no. 1), p. 3, sec. 3.5.
24.
For a study of particularistic uses of arguments to support and discount evidence, see G. Nigel Gilbert and Michael Mulkay, Opening Pandora's Box: An Analysis of Scientists' Discourse (Cambridge, UK: Cambridge University Press, 1984).
25.
Judgment, first appeal, 1996 (cit. no. 1), p. 3.
26.
Judgment, second appeal, 1997 (cit. no. 1), p. 3. The statement is confusing, because a match probability of 1 in 220 is much higher (and not lower, as the statement implies) than a probability of, for example 1 in 200 million. Perhaps the statement meant to say that including the brother would reduce the odds against the possibility of a profile from someone other than Denis John Adams matching the crime stain.
27.
For an illuminating discussion of how burden of proof for including particular persons in the suspect pool is shifted from prosecution to defense in DNA profiling cases, see Michael Redmayne, “Doubts and burdens: DNA evidence, probability and the courts,”Criminal Law Review (1995); 464-482.
28.
Thwaites and Brittain, (cit. no. 1), p. 4.
29.
Ibid., p. 5.
30.
Donnelly, quoted in Judgment, 1st Appeal, 1996.
31.
Ibid.
32.
Ibid.
33.
The 100 percent figure ignores the chance of a false negative (for example, a non-match between Adams's blood profile and the crime stain due to an error in the collection or analysis of the samples).
34.
This calculation must assume that the series of estimates covers all of the relevant evidence. They must be exhaustive. Otherwise, it would be inappropriate to make a guilty or not-guilty judgment on the basis of the series of estimates. It is obvious that the four items of defense evidence can be divided further. One could, for example, treat the witness's misidentification of Adams in the police line-up as a separate item from the mismatch between Miss M's description of the perpetrator's age and Adams's age. According to Donnelly (interview, cit. no. 1, p. 21), as long as all of the evidence is represented in the series of estimates, the overall calculation should, in principle, not be affected by the way it is parsed into separate items. Others, including a Mr. Lambert, who testified for the prosecution in the second trial, expressed misgivings on this point, arguing that the questionnaire that Donnelly prepared did not cover all of the relevant evidence, or all of the evidence that particular jurors might consider relevant (second appeal summary, cit. no. 1, p. 7).
35.
Donnelly also criticized the forensic scientists for not adding a correction factor for sampling error. This had a relatively minor effect (1 percent) on the resulting estimate.
36.
In a later case, R v. Watters (Court of Appeal [Criminal Division], October 19, 2000), the panel of judges on the Court held that DNA evidence without corroborating evidence was not sufficient to convict in that case. This judgment referred to the specific circumstances of the case; a burglary case in which an STR profile developed from a cigarette butt found at the crime scene matched the defendant's profile. The defendant had two brothers, and including them in the suspect pool greatly increased the probability that another person besides the defendant could have matched the crime scene evidence.
37.
An anonymous reviewer of the draft of this article commented that we make too much of the “ultimate issue,” because, in practice, it is often ignored and easily circumvented. We have no reason to doubt such an assessment, and if it is so that the “ultimate issue” is less than ultimate, then the Appeal Court's insistence upon its relevance should be viewed as a contingent way of settling the case at hand, rather than as an invocation of an omnirelevant and binding judicial principle for any comparable case.
38.
First appeal, (cit. no. 1), p. 15.
39.
Ibid.
40.
Ibid.
41.
Summing up of His Honour Judge Pownall, quoted in Second appeal, 1997, p. 8.
42.
A summary of Thwaites's arguments was presented in the Lord Chief Justice's summary, 2nd appeal, (cit. no. 1), pp. 5-8.
43.
Second appeal, (cit. no. 2), p. 10.
44.
R v Adams (1996) 2 Court of Appeal, R 467, cited in R v Doheny and Adams (1997) 1 Court of Appeal R 369, 374 G, which in turn is cited in Ibid., p. 11. <AU: please add note number to #44 above>
45.
The theme of judicial bootstrapping deserves more attention than we give it within the frame of this paper. See Gary Edmond and David Mercer, “Litigation life: law-science knowledge construction in (Bendectin) mass toxic tort litigation.”
46.
Second appeal, (cit. no. 1), p. 12.
47.
Interestingly, the court exemplified the “conventional” approach by describing how a juror might work through the various elements of the Adams case. This description included a sequence of probabilistic judgments, much as a Bayesian might describe them, except that the judgments would not be numerical.
48.
Second Appeal, (cit. no. 1), p. 13.
49.
Theodore Porter , Trust in Numbers: The Pursuit of Objectivity in Science and Public Life (Princeton: Princeton University Press, 1995).
50.
Ulrich Beck , Risk Society: Towards a New Modernity (London: Sage, 1992).
51.
and Alan Irwin and Brian Wynne (eds.), Misunderstanding Science? The Public Reconstruction of Science and Technology (Cambridge, UK: Cambridge University Press, 1996).
52.
See Steven Shapin, “Cordelia's love: credibility and the social studies of science,”Perspectives on Science3 (1995): 255-275.
53.
and H. M. Collins, Artificial Experts: Social Knowledge and Intelligent Machines (Cambridge, MA: MIT Press, 1990).
54.
It is possible to identify parallel themes between the sociology of scientific knowledge (SSK) and the arguments in an adversary trial (see Michael Lynch, “The discursive production of uncertainty: the O. J. Simpson `Dream Team' and the sociology of knowledge machine,”Social Studies of Science28, nos. 5/6 (1998): 829-868). However, it would be misleading to suppose that, in the Adams case, the participants in the trial are acting in accordance with the concepts and methodological strategies of SSK. It would be equally misleading to suppose that Thwaites and Donnelly lay out a position that is akin to a radically skeptical or “relativist” treatment of all knowledges as being “on a par with one another.” Thwaites and Donnelly seek to trump one “scientific” card (forensic DNA evidence) with another “scientific” (or mathematical) card (Bayesian probability). Their questionnaire is designed to allow jurors to weigh “scientific” (legal) evidence and “common sense” (legal) evidence on the same scale, but this circumscribed strategy does not suggest or imply a general hypothesis about “the causes” of credibility. Instead, it is a calculative device for inscribing and weighing credibility judgments.
55.
See Gieryn, “Boundary-work and the demarcation of science from non-science.”
56.
See State v. Steffen 230 N.W. 536 (Iowa, 1930).
57.
For a sociological discussion of procedural and statistical problems associated with early versions of DNA profiling, see Derksen, “For a sociology of measurement.” A key point in criticisms of court treatments of DNA profile evidence is that such evidence should be treated as “reports” by particular agents and agencies rather than simple scientific facts. Jonathan J. Kohler, “On conveying the probative value of DNA evidence: frequencies, likelihood ratios, and error rates,'University of Colorado Law Review67 (1996): 859-886, at 868.
58.
By the year 2000, probes were developed for as many as 13 DNA loci in the STR system. Estimates of more than one trillion to one were given against the odds against random matches between profiles from unrelated persons. With such impressive figures in hand, it has been argued that it will no longer be necessary even to consider the possibility that more than one person in the relevant suspect population could possibly match a given crime stain profile. Exceptions would be made for identical twins, and (with low likelihood) other very closely related persons. See Bruce Budowle, Ranajit Chakraborty, George Carmody, et al., “Source attribution of a forensic DNA profile,”Forensic Science Communications2, no. 3 (July, 2000) (available at: http://www.fbi.gov/programs/lab/fsc/backissu/july2000/source.htm).
59.
The position he developed in the interview is consistent with one he has held all along. For a non-technical account of his argument, see his Biology as Ideology: The Doctrine of DNA (New York: Harper Collins, 1992), 78-83.
60.
Ruth McNally, notes taken while attending second appeal, 17 October, 1997.
61.
For an argument against the policy of reporting match probabilities without taking laboratory errors (or evidence collection, mislabeling, etc.) into account, see William C. Thompson, “DNA evidence in the O. J. Simpson trial,”University of Colorado Law Review67 (1996): 827-857.
