Florida Trial Court Excludes the Opinion of a Latent Fingerprint Examiner — Maybe

Last week, Miami-Dade Circuit Court Judge Milton Hirsch issued an “order” stating that when the time comes in a burglary case, he will exercise his “common sense” to fulfill his “gatekeeping function” for scientific evidence under Florida law to prevent “excessive and unsupportable claims made by fingerprint examiners.” Order on Defendant's Motion in Limine, State v. Borrego, Nos. F12-101 & F12-7083, at 16 (Fla. Cir. Ct. Oct. 25, 2012) [cited as ODMIL]. One would not think that this promise would be horribly out of line.

Yet, the Miami Herald reported that outraged prosecutors now “vow to appeal” this “rare and controversial legal move.” David Ovalle, Miami-Dade Judge Rules Fingerprint Evidence Should Be Restricted, Miami Herald, Oct. 28, 2012. So what, exactly, is the shocking legal move here? Reviewing the three documents filed so far in the case, the judge's "order" looks more like a vague campaign pledge than a concrete judicial order amenable to interlocutory review.

The Defendant’s Motion

The defense asked for a specific ruling. It filed a pretrial motion for an order limiting the examiner’s testimony “to the similarities and dissimilarities he observed.” Defendant’s Motion in Limine, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct.) [cited as DMIL]. The ghost of U.S. District Court Judge Pollak’s perceptive (but then disowned) initial opinion in United States v. Llera Plaza rises just in time for Halloween. Andy Newman, Judge Rules Fingerprints Cannot Be Called a Match, N.Y. Times, Jan. 11, 2002.

In addition, the public defender asked for a series of “thou shalt nots. One would think that these would have been superfluous if the court made the first ruling. Nonetheless, the defense wanted an order prohibiting the analyst from speaking of a “match” or “identification,” and from stating his “level of confidence in his own testimony,” and from revealing or suggesting that a second examiner verified the match. DMIL at 2.

The defense did not rely on the general acceptance standard for scientific evidence that Florida follows. It could have. The Florida Supreme Court has applied the standard in a manner that resembles the direct inquiry into scientific validity mandated for federal courts in Daubert v. Merrell Dow Pharmaceuticals, and even a long history of use in police laboratories is not conclusive proof of general acceptance when a broader cross-section of the scientific community expresses doubts. David H. Kaye et al., The New Wigmore on Evidence: Expert Evidence (2d ed. 2011).

Instead of raising this threshold objection, however, the defense contended that a good fingerprint examiner is no better than a juror in forming a categorical opinion on the basis of the similarities and differences between an exemplar and a latent print DMIL at 2-3. This claim in highly problematic. Existing research may not be extensive, but it does support the view that trained examiners can outperform the laity. See Fingerprinting Error Rates Down Under, June 24, 2012.

Also implausibly, the defense argued that “match” necessarily means “absolute certainty” and somehow reached the conclusion that in recommending an end to testimony of “a source attribution to the exclusion of all others in the world,” DMIL at 4, the NIST report on latent fingerprinting supported the contention that no testimony about a “match” should be allowed. See Government-sponsored Report on Latent Fingerprint Work in Criminal Investigation and Prosecution, Feb. 18, 2012.

The defense advanced several other peculiar arguments. It maintained that the expert was unqualified to attribute a print to Borrego, even tentatively, because he lacked training or education in “population statistics or probabilities.” DMIL at 5. This qualifications argument has no force of its own. The real argument in this part of the public defender's memorandum is that fingerprint examiners do not follow the practice of DNA analysts of reporting probabilities “based on established scientific principles.” Id. at 6. A course in statistics and probability would not solve this problem. The gravamen of the complaint is not really the education of examiners. It is the practice of using personal judgment instead of a generally accepted statistical model.

Finally, the defense suggested, with no legal analysis, that “due process” and the “constitutional right to trial by jury, rather than trial by ‘expert’” justified “an order limiting Womack’s testimony to the parameters [sic] described herein.” Id at 8. In light of the normal opportunity to challenge excessive or dubious claims before a jury, however, the Fifth and Sixth Amendments do not add much, if anything, to the evidentiary argument.

The Prosecutor’s Reply

Rather than respond to any of these overblown arguments, the prosecution filed the State’s Motion to Disqualify Judge, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct. Oct. 15, 2012) [SMDJ]. (With unintended humor, the Miami Herald’s website refers to this as a “motion to rescue Judge Hirsch from the case.”) The motion stated that Judge Hirsch, in another case, had suggested that the prosecutor read his writings on fingerprint evidence and then said he would recuse himself if the state moved for his disqualification. On this basis, the prosecutor wrote that she entertained “a reasonable belief that Judge Hirsch will not be fair and impartial in ruling on any motions on fingerprint testimony.” SMDJ at 2.

Judge Hirsch was not swayed. He summarily denied the request. His Order Denying Motion to Disqualify Judge, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct. Oct. 25, 2012), is unedifying. But then again, the state’s theory that a judge must or should disqualify himself because he has written something on a subject or has stated a willingness to recuse himself in another case seems flimsy. These statements do not mean that a judge is incapable of making a fair ruling. Still, the state’s argument, if raised on appeal, might gain more traction if (as the Miami Herald reported) “Hirsch issued his order Thursday before prosecutors could write their reply to Borrego’s defense request to restrict the testimony of the fingerprint expert.”

The Order on the Fingerprint Testimony

The Order on Defendant’s Motion in Limine stretches across 17 pages. The court prepared and issued this sprawling “order” without a reply memorandum from the state. For that matter, neither does the document discuss the defendant’s argument about the education of the expert in probability and statistics. It surveys the history of science and scientific evidence, Florida’s adoption and application of the standard of general acceptance for such evidence, and a judge’s role in excluding evidence.

Then it turns to fingerprinting in literature and law. The court states that no problem arises when a fingerprint analyst merely displays the similarities and differences between two images. ODMIL at 13. This might be so if the examiner did not present himself as a forensic scientist, did not speak of the “science” of fingerprinting, did not refer to “the scientific method,” and insisted that he was present as little more than a photographer of images with no more skill than any juror to make the comparison. But even with all these fangs removed from the expert testimony, the admissibility of such testimony on ordinary relevance grounds is open to question. What intelligent use can jurors who know nothing about the variability of impressions of fingerprint features make of the images that are said to coincide sufficiently to be incriminating? Kaye et al., supra. Yet, the court seems to regard it as axiomatic that “[w]hen blow-ups, photographs, or other reproductions of fingerprints are admitted into evidence, the truth-seeking function of trials is advanced.” ODMIL at 14-15.

The Order castigates the most extreme testimony that fingerprint examiners once provided. Testimony that an identification can be made “to the exclusion of every other fingerprint in the history of the world” is “unsupportable.” Id. at 14. Testimony that “the error rate associated with their work, or with fingerprint examination in general, is zero” is“worse than wrong.” Id. Yet, the ensuing discussion of error rates from “human imperfections” is itself rather confused. The Order defines “error rate” as “false positives plus false negatives over total population.” ODMIL at 14. Whatever this means, it is not an “error rate” suitable for presentation to a jury. Kaye et al., supra. Moreover, contrary to the implication in the Order, it is not the “measurable error rate” used in “DNA analysis, the gold standard in forensic evidence.” Id. at 14. Like fingerprint examiners, DNA analysts do not normally present a rate of errors from “human imperfections,” and few of them would claim that human errors are impossible or never occur.

Thus, only this much of the Order is clear: The expert may not state that there is no chance at all that someone other than Radames Borrego left the fingerprints, that the association between Mr. Borrego and the latent prints is absolutely certain, or that mistakes are impossible. But beyond these limitations—which should be part of the profession’s own standards anyway—the Order is incredibly murky. It states that

a trial court must ... protect the integrity of the truth-seeking function from pollution and misdirection due to excessive and unsupportable claims made by fingerprint examiners. For a fingerprint witness to testify, "I direct the jury's attention to the arch appearing here, and the loop appearing here" is one thing; for a fingerprint witness to testify, "I have concluded that this fingerprint matches that of the defendant to the exclusion of all other fingerprints in the history of the world" is a very different thing. And in between these two very different things lie a thousand nuances and gradations of testimony. The trial judge must apply Frye, and Ramirez [a Florida Supreme Court case excluding testimony not generally accepted among toolmark analysts about the marks on cartilage], and his gatekeeping function, and his common sense, to each one of them when and as they are offered in evidence. [¶] And that is exactly what I intend to do at the trial of the case at bar.

Id. at 16.

The Bottom Line

So what do the 17 pages mean for the “thousand nuances and gradations” of testimony that are the subject of allusion rather than analysis? Would a description of relevant features followed by a qualitative statement of likelihoods be acceptable? Cf. Going South with Shoeprint Testimony, July 14, 2012. How about a statement that Mr. Borrego cannot be excluded as the source, although most people could be? Would the judge's "common sense" allow the observation that the prints in question are far more consistent with each other than randomly selected ones? May the examiner opine that the prints “match” as that term is used in the field, while adding that this match does not mean no one else in the world also might have a finger that would produce a matching image? Cf. Who Is Nelson Acosta-Roque? (Part III).

The operative part of the Order is not helpful here. It reads, “Defendant's motion in limine is respectfully GRANTED only to the extent of the foregoing order” ODMIL at 16. It is fine to enliven opinions with poetry, as this one does, but some precision in evidentiary rulings would be more useful to the parties.

References

• Order on Defendant's Motion in Limine, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct. Oct. 25, 2012)
• Order Denying Motion to Disqualify Judge, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct. Oct. 25, 2012)
• Defendant’s Motion in Limine, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct.)
• State’s Motion to Disqualify Judge, State v. Borrego, Nos. F12-101 & F12-7083 (Fla. Cir. Ct. Oct. 15, 2012)
• David H. Kaye et al., The New Wigmore on Evidence: Expert Evidence (2d ed. 2011)
• David Ovalle, Miami-Dade Judge Rules Fingerprint Evidence Should Be Restricted, Miami Herald, Oct. 28, 2012, http://www.miamiherald.com/2012/10/28/v-fullstory/3071658/miami-dade-judge-rules-fingerprint.html
• Fingerprinting Error Rates Down Under, June 24, 2012, http://for-sci-law-now.blogspot.com/2012/06/fingerprinting-error-rates-down-under.html
• Going South with Shoeprint Testimony,  July 14, 2012, http://for-sci-law-now.blogspot.com/2012/07/going-south-with-shoeprint-testimony.html
• Who Is Nelson Acosta-Roque? (Part III). http://for-sci-law-now.blogspot.com/2012/06/who-is-nelson-acosta-roque-part-iii.html
• Government-sponsored Report on Latent Fingerprint Work in Criminal Investigation and Prosecution, Feb. 18, 2012, http://for-sci-law-now.blogspot.com/2012/02/government-funded-report-on-latent.html

Acknowledgments: Thanks to Professor Joelle Moreno for calling the case to my attention.

More on Semrau: The Other Daubert Factors

In United States v. Semrau, the U.S. Court of Appeals for the Sixth Circuit upheld the exclusion of a defendant’s “unilateral” fMRI testing for conscious deception. Previously, I focused on the court’s discussion of error rates. Known error rates implicate admissibility under both Federal Rule of Evidence 702 and Federal Rule 703. (Rule 702 is the locus of the scientific validity standard adopted in Daubert v. Merrell Dow Pharmaceutics, and Rule 703 states the common law, ad hoc balancing test for virtually all evidence.) I do not think the opinion is as clear as it could have been on which error rate pertained to what. Nevertheless, it is encouraging that the court recognized that two parameters are necessary to describe the accuracy of a procedure that classifies items or people into two categories (liar or truth teller).

But Daubert's list of factors extends beyond error rates, and the Semrau court’s handling of the other Daubert subissues also merits a mixed review. First, the court suggested that fMRI lie detection satisfied Daubert’s criteria for testing and peer review. It referred to “several factors in Dr. Semrau's favor,” namely:

“[T]he underlying theories behind fMRI-based lie detection are capable of being tested, and at least in the laboratory setting, have been subjected to some level of testing. It also appears that the theories have been subjected to some peer review and publication.” Semrau, 2010 WL 6845092, at *10. The Government does not appear to challenge these findings, although it does point out that the bulk of the research supporting fMRI research has come from Dr. Laken himself.

The suggestion that these factors favor the defendant treats Daubert’s references to testing, peer review, and publication rather superficially. That a scientific theory is “capable of being tested” tells us almost nothing about the validity of the theory. The theory that in the year 2075, the moon will turn into a blob of green cheese is capable of being tested, but that does not help validate it today. Likewise, the mere existence of peer reviewed publications means nothing without examining the content of the publications and the reactions to them in the scientific literature.

The court came closer to addressing the true Daubert issue of whether peer reviewed publications,  considered as a whole, validate a technique or theory when it responded to defendant’s argument that the district court was overly concerned with the realism of validity studies.  In that context, the court of appeals quoted the caveat in one fMRI study that:

This study has several factors that must be considered for adequate interpretation of the results. Although this study attempted to approximate a scenario that was closer to a real-world situation than prior fMRI detection studies, it still did not equal the level of jeopardy that exists in real-world testing. The reality of a research setting involves balancing ethical concerns, the need to know accurately the participant's truth and deception, and producing realistic scenarios that have adequate jeopardy.... Future studies will need to be performed involving these populations.

But even this mention of the content of one study does not explain why the experiments are inadequate to demonstrate validity. Why would it be harder to detect a lie that has grave consequences to the subject of the laboratory experiment or field study than one that has more trivial consequences?

Second, the court of appeals wrote that the “controlling standards factor” had not been satisfied because “[w]hile it is unclear from the testimony what the error rates are or how valid they may be in the laboratory setting, there are no known error rates for fMRI-based lie detection outside the laboratory setting, i.e., in the ‘real-world’ or ‘real-life’ setting.” But what does the realism of laboratory experiments have to do with the existence of a clear protocol for gathering and interpreting data? Naturally, if a test is not standardized, it is hard to ascertain its error rate—a point that has been prominent in debates over fingerprinting. And, if the tester departs slightly from the standard test protocol, the probative value of the test should be questioned under Rule 403. But the issue of external validity should not be confused with the issue of whether standards are in place for administering a test.

Finally, the court implied that without realistic field testing, there could be no general scientific acceptance of a method of lie detection in the forensic setting. This may be true, but all empirical studies pertain to particular times, places, and subjects. Deciding what generalizations are reasonable or generally accepted depends on understanding the phenomena in question. Can laboratory experiments alone show that certain factors tend to affect the accuracy of eyewitness identifications? For years, many experimental psychologists seemed willing to accept forensic applications of laboratory results that lacked complete realism. The ability of fingerprint examiners to match true pairs of prints and exclude false pairs of prints can be demonstrated in laboratory studies with artificially created pairs. Applying the error rates from such laboratory experiments to actual forensic setting could well be hazardous, but the experiments still prove that there is information that analysts can use to make valid judgments. In that situation, it is doubtful that raising the stakes of a judgment will render the technique invalid.

The Semrau court does not pinpoint the source of its discomfort with pure laboratory experiments. As we have just seen, a court should not assume that laboratory experiments never can establish validity of a technique as applied to casework. However, in the case of fingerprint identification, it seems clear enough that the prints do not change depending on whether they are deposited in the course of a crime or produced at another location. The fMRI data might well be different when generated under fully realistic circumstances. As a result, proving that there is detectable brain activity specific to conscious deception under low stakes conditions might not establish that the same pattern arises under high stakes conditions. Without a generally accepted theory of underlying mechanisms to justify extrapolations to the usual conditions of casework, low stakes laboratory findings may not suffice show general acceptance of validity under those conditions.

In sum, Semrau should not be read as establishing that the existence of testability carries any significant weight in favor of admission, that publication in a peer reviewed journal necessarily demonstrates validity, that a lack of complete realism in laboratory studies proves that there  are no “controlling standards” in practice, or that only field studies can establish general acceptance.

These concerns about the wording of the opinion notwithstanding, the problem of generalizing from the laboratory studies to the conditions of the Semrau case are substantial, and the court’s conclusion is difficult to dispute.

True Lies: fMRI Evidence in United States v. Semrau

This month, the U.S. Court of Appeals for the Sixth Circuit issued an opinion on “a matter of first impression in any jurisdiction.” The case is United States v. Semrau, No. 11-5396, 2012 WL 3871357 (6th Cir. Sept. 7, 2012). Its subject is the admissibility of the latest twist, the ne plus ultra, in lie detection—functional magnetic resonance imaging (fMRI).

In several ways, the case resembles what may well be the single most cited case on scientific evidence—namely, Frye v. United States, 293 F. 1013 (D.C. Cir. 1923). Frye instituted a special test for admitting scientific evidence. In Frye, a defense lawyer asked a psychologist, Dr. William Moulton Marston, who had developed and published studies of a systolic blood pressure test for conscious deception, to examine a young man accused of murdering a prominent physician. Dr. Marston came to Washington and was prepared to testify that the accused was truthful in retracting his confession to the murder. The trial court would not hear of it. The jury convicted. The defendant appealed. In a short opinion pregnant with implications, the Court of Appeals for the District of Columbia affirmed the exclusion of the expert’s opinion that the defendant was not lying to him.

In United States v. Semrau, defense counsel invited Dr. Steven Laken to examine the owner and CEO of two firms accused of criminal fraud in billing Medicare and Medicaid for psychiatric services that the firm supplied in nursing homes. Like Marston, Dr. Laken, had invented and published on an impressive method of lie detection. Following three sessions with the defendant, Dr. Laken concluded that the accused “was generally truthful as to all of his answers collectively.” As in Frye, the district court excluded such testimony. As in Frye, a jury convicted. As in Frye, the defendant appealed. As in Frye, the court of appeals affirmed.

Dr. Marston held degrees from Harvard in law and in psychology. He worked hard to develop and popularize psychological theories (and he created the comic book character, Wonder Woman). Like Marston, Dr. Laken is highly creative, productive, and enterprising. Dr. Laken started his scientific career in genetics and cellular and molecular medicine. He achieved early fame for discovering a genetic marker and developing a screening test for an elevated risk of a form of colon cancer. For that accomplishment, MIT’s Technology Review recognized him as one of the most important 35 innovators under the age of 35 and noted that “Laken believes his methods could spot virtually any illness with a genetic component, from asthma to heart disease.” I do not know if that happened. After four years as Director of Business Development and Intellectual Asset Management at Exact Sciences, a “molecular diagnostics company focused on colorectal cancer,” Laken left genetic science to found Cephos, “the world-class leader in providing fMRI lie detection, and in bringing fMRI technology to commercialization.”^1/

Despite these parallels, Laken is not Marston, and Semrau is not Frye. For one thing, in Frye, the trial judge excluded the evidence without an explanation. In Semrau, the trial judge had a magistrate conduct a two-day hearing. Two highly qualified experts called by the government challenged the validity of Dr. Laken’s theories, and the magistrate judge wrote a 43-page report recommending exclusion of the fMRI testimony from the trial.^2/

Furthermore, in Frye, there was no previous body of law imposing a demanding standard on the proponents of scientific evidence—the Frye court created from whole cloth the influential “general acceptance” test.^3/ In Semrau, the court began with the Federal Rules of Evidence, ornately embroidered with the Supreme Court's opinions in Daubert v. Merrell Dow Pharmaceuticals and two related cases and with innumerable lower court opinions applying the Daubert trilogy. This legal tapestry requires a showing of “reliability” rather than “general acceptance,” and it usually involves attending to four or five factors relating to scientific validity enumerated in Daubert.^3/ I want to look briefly at a few of these in the context of Semrau.

* * *
Even though the only judges to address fMRI-based lie detection (those in Semrau) have deemed it inadmissible under both the Daubert standard (and under the Frye criterion of general acceptance), Cephos continues to advise potential clients that “[t]he minimum requirements for admissibility of scientific evidence under the U.S. Supreme Court ruling Daubert v. Merrell Dow Pharmaceuticals, are likely met.” One can only wonder whether its “legal advisors,” such as Dr. Henry Lee (see note 1), are comfortable with Cephos’s reasoning that

According to a PubMed search, using the keywords ”fMRI” or “functional magnetic resonance imaging” yields over 15,000 fMRI publications. Therefore, the technique from which the conclusions are drawn is undoubtedly generally accepted.

The reasoning is peculiar, or at least incomplete. The sphygmomanometer that Dr. Marston used also was “undoubtedly generally accepted.” This pressure meter was invented in 1881, improved in 1896, and modernized in 1901, when Harvey Cushing popularized the device in the medical community. However, the acknowledged ability to measure systolic blood pressure reliably and accurately does not validate the theory—which predated Marston—that blood pressure is a reliable and valid indicator of conscious deception. Likewise, the number of publications about fMRI in general—and even particular evidence that it is a wonderful instrument with which to measure blood oxygenation levels in parts of the brain—reveals very little about the validity of the theory that these levels are well correlated with conscious deception. To be sure, there is more research on this association than there was on the blood pressure theory in Frye, but the Semrau courts were not overly impressed with applicability of the experimentation to the examination conducted in the case before it.^4/

* * *
In addition to directing attention to general acceptance, Daubert v. Merrell Dow Pharmaceuticals identifies “the known or potential rate of error in using a particular scientific technique” as a factor to consider in determining “evidentiary reliability.” The Daubert Court took this factor from circuit court cases involving polygraphy and “voiceprints.” Unfortunately, the ascertainment of meaningful error rates has long confused the courts,^5/ and the statistics in Semrau are not presented as clearly as one might hope.

According to Cephos, “[p]eer review results support high accuracy,” but this short statement begs vital questions. Accuracy under what conditions? How “high” is it? Higher for diagnoses of conscious deception than for diagnoses of truthfulness, or vice versa? The court of appeals began its description Semrau’s evidence on this score as follows:

Based on these studies, as well as studies conducted by other researchers, Dr. Laken and his colleagues determined the regions of the brain most consistently activated by deception and claimed in several peer-reviewed articles that by analyzing a subject's brain activity, they were able to identify deception with a high level of accuracy. During direct examination at the Daubert hearing, Dr. Laken reported these studies found accuracy rates between eighty-six percent and ninety-seven percent. During cross-examination, however, Dr. Laken conceded that his 2009 “Mock Sabotage Crime” study produced an “unexpected” accuracy decrease to a rate of seventy-one percent. ...

But precisely what do these “accuracy rates” measure? By “identify deception,” does the court mean that 71%, 86%, and 97% are the proportions of subjects who were diagnosed as deceptive out of those whom the experimenters asked to lie? If we denote a diagnosis of deception as a “positive” finding (like testing positive for a disease), then such numbers are observed values for the sensitivity of the test. They indicate the probability that given a lie, the fMRI test will detect it—in symbols, P(diagnose liar | liar), where “|” means “given.” The corresponding conditional error probability is the false negative probability P(diagnose truthful | liar) = 1 – sensitivity. It is the probability of missing the act of lying when there is a lie.

So far so good. But it takes two probabilities to characterize the accuracy of a diagnostic test. The other conditional probability is known as specificity. Specificity is the probability of a negative result when the condition is not present. In symbols that apply here, the specificity is P(diagnose truthful | truthful). Its complement, 1 – specificity, is the false positive, or false alarm, probability, P(diagnose liar | truthful). That is, the false alarm probability is the probability of diagnosing the condition as present (the subject is lying) when it is absent (the subject actually is not lying). What might the specificity be? According to the court,

Dr. Laken testified that fMRI lie detection has “a huge false positive problem” in which people who are telling the truth are deemed to be lying around sixty to seventy percent of the time. One 2009 study was able to identify a “truth teller as a truth teller” just six percent of the time, meaning that about “nineteen out of twenty people that were telling the truth we would call liars.” . . .

Why was this not a problem for Dr. Laken in this case? Well, the fact that the technique has a high false positive error probability (that it classifies most truthful subjects as liars) does not mean that it also has a high false negative probability (that it classifies most lying subjects as truthful). Dr. Laken conceded that the false positive probability, P(diagnose liar | truthful), is large (around 0.65, from the paragraph quoted immediately above). Indeed the reference to 6% accuracy for classifying liars (the technique’s sensitivity to lying), corresponds to a false positive probability of 100% – 6% = 0.94. The average figure for this false alarm probability, according to Dr. Laken’s statements in the preceding quoted paragraph, is lower, but it is still a whopping 0.65. Nevertheless, if the phrase “accuracy rates” in the first quoted paragraph refers to specificity, then the estimates of specificity that he provided are respectable. The average of 0.71, 0.86, and 0.97 is 0.85.

What do these numbers prove? One answer is that they apply only under the conditions of the experiments and only to subjects of the type tested in these experiments. The opinions take this strict view of the data, pointing out that the experimental subjects were younger than Semrau and that they faced low penalties for lying. Indeed, the court explained that

Dr. Peter Imrey, a statistician, testified: “There are no quantifiable error rates that are usable in this context. The error rates [Dr. Laken] proposed are based on almost no data, and under circumstances [that] do not apply to the real world [or] to the examinations of Dr. Semrau.”

These remarks go largely to the Daubert question. If the experiments are of little value in estimating an error rate in populations that would be encountered in practice, then the validity of the technique is difficult to gauge, and Cephos’s assurance that this factor weighs in favor of admissibility is vacuous. If there is no way to estimate the conditional error probability for the examination of Semrau, then it is hard to conclude that the test has been validated for its use in the case.

* * *
Fair enough, but I want to go beyond this easy answer. Psychologists often are willing to generalize from laboratory conditions to the real world and from young subjects (usually psychology students) to members of the general public. So let us indulge, at least arguendo, the heroic assumption that the ballpark figures for the specificity and the false alarm probability apply to defendants asserting innocence in cases like Semrau. On this assumption, how useful is the test?

Judging from the experiments as described in the court of appeals opinion, if Semrau is truthful in denying any intent to defraud, there is roughly a 0.85 probability of detecting it, and if he lies, there is maybe a 0.65 probability of misdiagnosing him as truthful. So the evidence—the diagnosis of truthfulness—is not much more probable when he is truthful than when he is lying. As such, the fMRI diagnosis of truthfulness has little probative value. (The likelihood ratio is .85/.65 = 1.3.)

That a diagnosis of deception is almost as probable for truthful subjects as for mendacious ones bears mightily on the Rule 403 balancing of prejudice against probative value. The court held that this balancing justified exclusion of Dr. Laken’s testimony, largely for reasons that I won’t go into.^6/ It referred to questions about “reliability” in general, but it did not use the error probabilities to shed a more focused light on the probative value of the evidence.

However, it seems from the opinion that Dr. Laken offered at least one probability to show that his diagnosis was correct. The court noted that

Dr. Imrey also stated that the false positive accuracy data reported by Dr. Laken does not “justify the claim that somebody giving a positive test result ... [h]as a six percent chance of being a true liar. That simply is mathematically, statistically and scientifically incorrect.”

It is hard to understand what the “six percent chance” for “somebody giving a positive test result” had to do with the negative diagnosis (not lying) for Semrau. A jury provided with negative fMRI evidence (“He was not lying”) must decide whether the result is a true negative or a false negative—not what might have happened had there been a positive diagnosis.

As for the 6% solution, it is impossible to know from the opinion how Dr. Laken arrived at such a number for the probability that a subject is lying given a positive diagnosis. The conditional probabilities from the experiments run in the opposite direction. They address the probability of evidence (a diagnosis) given an unknown state of the world (a liar or a truthful subject). If Dr, Laken really opined on the probability of the state of the world (a liar) given the fMRI signals, then he either was naively transposing a conditional probability—a no-no discussed many times in this blog—or he was using Bayes’ rule. In light of Dr. Imrey’s impeccable credentials as a biostatistician and his unqualified dismissal of the number as “mathematically, statistically and scientifically incorrect,” I would not bet on the latter explanation.

Notes

1. If the firm’s website is any indication, it is not an equivalent leader in good grammar. Apparently seeking the attention of wayward lawyers, it advertises that “[i]f you or your client professes their innocence, we may provide pro bono consulting.” The website also offers intriguing reasons to believe in the company’s prowess: it is “represented by one of the top ten intellectual property law firms”; it has “been asked to present to the ... Sandra Day O’Connor Federal Courthouse”; and its legal advisors include Dr. Henry C. Lee (whose website includes “recent sightings of Dr. Lee.”). In addition to its lie-detection work, Cephos offers DNA testing, so perhaps I should not say that Dr. Laken has withdrawn entirely from genetic science.

2. The court of appeals buttressed its approval of the report with the observation that “Professor Owen Jones, who observed the hearing” and is on the faculties of law and biology at Vanderbilt University, stated in an interview with Wired, that the report was “carefully done.”

3. For elaboration, see David H. Kaye, David E. Bernstein & Jennifer L. Mnookin, The New Wigmore: A Treatise on Evidence—Expert Evidence (2d ed. 2011) http://www.aspenpublishers.com/product.asp?catalog_name=Aspen&product_id=0735593531

4. For a short discussion of validity in this context, see Francis X. Shen & Owen D. Jones, Brain Scans as Evidence: Truths, Proofs, Lies, and Lessons, 62 Mercer L. Rev. 861 (2011),

5. See David H. Kaye, David E. Bernstein & Jennifer L. Mnookin, The New Wigmore: A Treatise on Evidence—Expert Evidence (2d ed. 2011).

6. The court appeals wrote that “the district court did not abuse its discretion in excluding the fMRI evidence pursuant to Rule 403 in light of (1) the questions surrounding the reliability of fMRI lie detection tests in general and as performed on Dr. Semrau, (2) the failure to give the prosecution an opportunity to participate in the testing, and (3) the test result's inability to corroborate Dr. Semrau's answers as to the particular offenses for which he was charged.”

Dear Judges: A Letter from the Electronic Frontier Foundation to the Ninth Circuit

On the eve of the en banc oral argument in Haskell v. Harris, The Electronic Frontier Foundation (EFF) filed a letter asking "the Court to consider the ENCODE project findings in determining the outcome of this case." It seems hard to oppose the idea that the court should consider relevant scientific research, but without input from the scientific community, will the judges do better than they have in the past as "amateur scientists" (to use the skeptical phrase of Chief Justice Rehnquist in Daubert v. Merrell Dow Pharmaceuticals, Inc.)?

Deciphering the ENCODE papers' descriptions of the data is no easy task, and EFF's lawyers do not seem to be up to it. Their letter asserts that the project "has determined that more than 80% of DNA once thought to be no more than 'junk' has at least one biochemical function, controlling how our cells, tissue and organs behave." This is not a fair characterization of the findings. Which geneticist ever claimed that all noncoding DNA plays no role in how cells behave? The issue always has been how much junk, how much func -- and what "functions"?

What does EFF mean by "controlling"? Making organs function? Stimulating tissue growth? Turning normal cells into cancerous ones? Making us tall or short, fat or skinny, gay or straight? None of those things are mentioned in the Nature cover story cited in the letter. Instead, the EFF relies on New York Times reporter Gina Kolata's misleading news article for EFF's claim that "The ENCODE project has determined that 'junk' DNA plays a critical role in determining a person’s susceptibility to disease and physical traits like height."

My earlier postings described the limited meaning of the phrase "biochemical function" in the cited paper. I'd love to see a citation to a page of an ENCODE paper that asserts that fully 80% of the noncoding DNA is determining "susceptibility to disease and physical traits like height." And if I were a judge, I would demand an explanation of why "physical traits like height" are, in the words of the EFF letter, "sensitive and private."

After the judges consider the ENCODE papers (by having their law clerks read them?), will they be better informed about the actual privacy implications of the CODIS loci than they were before this excursion into this realm of the bioinformatics? I would not bet on it, but maybe I am growing cynical.

On the "clear" outcome of "established" law

Today's New York Times included an editorial (California and the Fourth Amendment) on Haskell v. Harris, the challenge to the California Proposition requiring DNA sampling on arrest. En banc oral argument takes place today. The following is a letter I sent to the Times editor. I expect somewhere between 0 and 50 percent of it to be published there (point estimate = 0):

Dear Editor,

Your editorial (September 19) asserts that the constitutionality of taking DNA on arrest “should be clear” given “established rights against unreasonable search and seizure.” Yet, over vigorous dissents, federal courts of appeals have ruled otherwise—twice in panels of the Ninth Circuit and once in the Third Circuit.

Whether acquiring purely biometric data from arrestees necessitates a warrant is doubtful, and whether acquiring DNA data is “unreasonable” is a close question. The physical invasion of personal security is minor when the individual is already in custody and the sampling is only marginally more intrusive than fingerprinting. The medical information content of the identification profile is (given current knowledge) only slightly more significant than that of a fingerprint. Very few false convictions arising from DNA database searches have been documented. (One in Australia has been reported.)

Contrary to the suggestion in the editorial, what divided the judges in the Ninth Circuit was not whether “the law’s real purpose was investigation.” No one doubted that. The dissenting judge believed that the Supreme Court already had decided that “fingerprints may not be taken from an arrestee solely for an investigative purpose, absent a warrant or reasonable suspicion that the fingerprints would help solve the crime for which he was taken into custody.” What the Court actually held was “that transportation to and investigative detention at the station house without probable cause or judicial authorization together violate the Fourth Amendment.” The dissenting judge also worried, among other things, that “it is possible that ... at some future time,” an identification profile might permit strong inferences about the diseases an arrestee has or might develop.

I do not claim that arrestee DNA sampling clearly is constitutional. There are a number of valid concerns about indefinite sample retention and other matters. Neither do I maintain that its benefits (which are not well quantified) plainly outweigh its costs and its impact on legitimate interests in personal privacy and security. But assertions that the balance is “clear” and that the “established” law dictates the result oversimplify a delicate constitutional question.