Voice Stress Analysis and the Investigation of Trayvon Martin's Death

Today’s New York Times has a lengthy article [1] on the flaws in the Sanford, Florida, police investigation of the shooting of black teenager, Trayvon Martin, by the 28-year-old neighborhood watch volunteer, George Zimmerman. When the 16-day investigation did not produce any charges, Florida’s governor responded to a national outcry by appointing an aggressive prosecutor. Now indicted, Zimmerman continues to maintain that he shot Martin in self-defense.

Tucked away at the end of the article is the single sentence: “The police conducted a lie-detection procedure, known as voice stress analysis, on Mr. Zimmerman that [sic] he passed.” A voice-stress test? By “a small city police department that does not even have a homicide unit and typically deals with three or four murder cases a year”? [1]

Yes, law enforcement agencies across the country have invested millions of dollars in voice stress analysis (VSA) software programs—despite a widely known lack of evidence to show that they work. For example, after conducting a field study of jail inmates using urinalysis to check their statements about whether they had used specific drugs, a University of Oklahoma researcher wrote that “two of the most popular VSA programs in use by police departments across the country are no better than flipping a coin when it comes to detecting deception regarding recent drug use [2]." 1/

The response of the National Institute for Truth Verification—the company that bills itself as “the world leader in voice stress analysis”—is instructive. The company’s website insists that

the vast majority of VSA studies funded by pro-polygraph elements of the US Government were significantly flawed. One of the many flaws of these studies . . . was that they lacked real-life consequence and thus lacked jeopardy. . . . [C]onsequence and jeopardy found in “high stakes lies” are required to accurately and consistently detect deception. [¶] . . . VSA research conducted by the University of Florida, and a second study conducted by researchers from the University of Oklahoma, both utilized “low stakes lies” in an attempt to measure the results of various VSA instruments. [3]

Another webpage on validity lists many studies, but the descriptions indicate that they merely demonstrate that VSA can detect stress and anxiety. [4] The question, as with the polygraph, is whether an examiner can ascertain the cause of the stress. Thus, the defense of VSA seems be this: we have no scientifically respectable body of proof showing that VSA is highly sensitive and specific in detecting deception, but, then again, nobody has proven to our satisfaction that it does not work for this purpose.

Despite the inability to validate VSA, some police love it. A detective in the Sex Crimes Section of the Metropolitan Nashville Police Department explained that:

We purchased 10 CVSA's and trained 20 examiners and in my opinion, the instruments and training have been one of the greatest assets our department has ever acquired. Not only has it helped us solve many crimes from major thefts to homicides, but has also helped expose false reports from victims, thus saving our department many man-hours of investigation. [5]

Considering that the fundamental question about VSA is whether it can distinguish between stress caused by intentional deception and stress caused other factors—think about the rape victim who has to describe the events to the police—this kind of screening is a little frightening. It helped the Sanford police and prosecutor, though. Or did it?

Notes

1. The comparison to a coin may be misleading. Consider Table 12 in the Oklahoma study. Kelly R. Damphousseat et al., Assessing the Validity of Voice Stress Analysis Tools in a Jail Setting, Mar. 31, 2007, at 53 (NCJRS doc. no. 219031, available at https://www.ncjrs.gov/pdffiles1/nij/grants/219031.pdf). It indicates that 87 subjects tested positive for cocaine use within the past 72 hours. Of these, 40 deceptively stated that they had not used cocaine in this period. However, VSA programs only correctly indicated deception for eight of the 40. This is a sensitivity of 20%. Given an individual lying about recent cocaine use, the programs had only one chance in five of recognizing the deception. However, Their specificity was much better. Of the 47 respondents who were not deceptive, the programs correctly classified 42 (89%) as truthful. A coin flip, on the other hand, would have a specificity and sensitivity of 50%. See, e.g., David H. Kaye, The Validity of Tests: Caveant Omnes, 27 Jurimetrics J. 349 (1987).

References

1. Serge F. Kovaleski, Trayvon Martin Case Shadowed by Series of Police Missteps, N.Y. Times, May 16, 2012

2. Kelly R. Damphousse, Voice Stress Analysis: Only 15 Percent of Lies About Drug Use Detected in Field Test, NIJ Journal No. 259, Mar. 17, 2008

3. National Institute for Truth Verification, Research Casts Doubt on US Government-Funded VSA Studies

4. National Institute for Truth Verification, Studies Validating Voice Stress Analysis

5. Kent McAllister, quoted in National Institute for Truth Verification, Law Enforcement Reviews

ASCLD Meets Frontline

On April 17, PBS aired a Frontline documentary on “The Real CSI.” Within the week, the president of the American Society of Crime Lab Directors (ASCLD), Jill Spriggs, gave the following assessment to her fellow crime lab directors:

In the last week, published reports dusted off the same old forensic cases from the past and regurgitated negative information from years ago in order to provide doubt in the minds of the public and the court. I don’t know about you but some of my neighbors watched the Frontline documentary and had many questions. “Were latent prints really not a validated science?” “Is latent print analysis not what I thought it is?” “Were bite marks really a product of bad forensic science?” “How could anyone rely on bite marks?” “And, how many employees use certificate mills to obtain a forensic science certification?” My answer—You can be confident about latent print evidence. Latent prints are a validated science. Of all of the millions of fingerprint samples in the databases throughout the world, no two people have ever matched the same fingerprint. Bite marks are not an accredited crime laboratory discipline and “no” we don’t use forensic science certification mills to certify our analysts.

Watching the documentary, I shared her sense of boring familiarity. What’s new here? Same faces, same criticisms. But Ms. Spriggs’ rejoinder likewise is outdated in the logic it uses to shrug off the criticisms. Frontline summarized real problems with the way the American criminal justice system produces and consumes forensic science evidence. Although ASCLD is not responsible for these problems, let’s look more carefully at the three matters that Ms. Spriggs mentions.

1. Credible Credentials

In case after case, witnesses bolster their credentials as forensic experts with credentials from the American College of Forensic Examiners Institute—the organization depicted as a diploma mill on the Frontline show (and elsewhere). Courts often take the bait. For example, in People v. McWhorter, 212 P.3d 692 (Cal. 2009), the California Supreme Court juxtaposed a defense expert’s seemingly strong credentials—he “was certified by an organization known as the American Board of Recorded Evidence; and was a member of the American College of Forensic Examiners” with his puzzling inability to “identify the computer program he used to enhance or ‘electronically emboss’ the image in question [and to] satisfactorily explain the full nature of the process he used to create it.” Id. at 726.

It is appropriate to note that “we [all government crime labs?] don’t use forensic science certification mills to certify our analysts.” But what about the rest of the forensic science community—and the courts? Some prosecutors seem to have no compunction about presenting their witnesses as qualified at least in part because they are “a life fellow for The American College of Forensic Examiners” or some such thing. Chavarria v. State, 307 S.W.3d 386, 387 (Tex. Ct. App. 2009).

Judges and lawyers need to learn which organizations have meaningful standards and which do not. If there were less demand for dubious credentials, expert witnesses—government employees and private consultants alike—would have less incentive to pad their CVs with such credentials.

2. “Bite marks are not an accredited crime laboratory discipline”

Disavowing bite-mark evidence because it comes from outside the public laboratory is not responsive to the question, “Were bite marks really a product of bad forensic science?” Does ASCLD believe that forensic science is limited to the reports of crime laboratories? That forensic odontologists are not accredited? The American Board of Forensic Odontology "was organized in 1976 under the auspices of the National Institute of Justice" and "is accredited by the Forensic Specialties Accreditation Board (FSAB) as a forensic specialty offering board certification to qualified forensic dentists." If the public cannot trust this field's accredited expertise, why should it trust "an accredited crime laboratory discipline"? (There are a number of possible answers, but Ms. Spriggs does not provide them.)

3. “You can be confident about latent print evidence. Latent prints are a validated science.”

Latent prints often contain valuable information for ascertaining the origin of the print. However, the Frontline interviewees pointed to the lack of objective criteria for deciding when prints do or do not come from the same source and the danger that unconscious bias could influence these judgments. These problems notwithstanding, there are scientifically sound studies suggesting that latent fingerprint examiners can get the correct answers most of the time. The Frontline show could be faulted for failing to acknowledge this research while publicizing the NIJ’s refusal to fund a rigorous, comprehensive audit of actual laboratory work. Such a study should be done to complement the recently acquired experimental data, but why would Frontline omit these findings from its televised and online materials?

Yet, Ms. Spriggs does the same thing. Rather than refer to the scientific research that is responsive to the calls for better validation, she repeats the same old story: We can have great confidence in the work of latent print analysts because “[o]f all of the millions of fingerprint samples in the databases throughout the world, no two people have ever matched the same fingerprint.”

What is wrong with this proof of validity? First, whether any individuals have the same fingerprint tells us virtually nothing about the ability of analysts to compare prints accurately. In the Frontline show, Jennifer Mnookin made this point when she explained that the task confronting a latent print analyst is to discern when a partial print comes from a particular person’s finger. That task is distinct from deciding whether pairs of full prints come from different fingers.

Second, just because there are millions of prints on file, it hardly follows that “the millions of fingerprint samples in the databases throughout the world” match. The FBI alone has over 71 million prints in its database. To verify that no pair of these exemplar prints match would require approximately 2.5 x 10¹⁵ (2.5 quadrillion) comparisons of pairs of 10 prints. It would take an examiner, working at the incredible pace of one comparison per digit per second, some 800 million years to complete this task. When the FBI’s contractor, Lockheed Martin, tried to prove the non-existence of matching prints in the database using an automated matcher, it limited itself to a mere 51,000 prints and failed to establish uniqueness.

Ms. Spriggs importuned her fellow crime lab directors to “speak out on these issues. . . . Don’t wait another day! Get started!” Indeed, there are important things to be said.

Earprints Leave Their Mark in Germany

Der Spiegel recently reported that "earprints . . . are as useful to the police as finger prints. A burglar in Germany made the mistake of pressing his ear to front doors to check if anyone was home. The unique prints have allowed the police to pin 96 burglaries on him" [1].

The article makes no mention of the flap over earprints in England [2]. In 1998, a small-time burglar named Mark Dallagher made legal history when he became the first man to be convicted of murder by earprint evidence [3]. A jury found him guilty of murdering 94-year-old Dorothy Woods after Cornelis van der Lugt, a Dutch earprint expert, said he was "absolutely convinced" that Dallagher had made the prints found on the window of Miss Wood's house [3]. Eventually, however, DNA was recovered from the earprints, and it did not match Dallagher's. Following "an appeal, a retrial and a fresh police investigation the Crown said it had 'anxieties' about the case and was offering no evidence against Dallagher'" [3]. Thus, he was acquitted of the murder in 2004 [3].

Despite the bad press the Dallagher case generated, "earprints" are not without value in criminal investigations. Obviously, earmarks vary across individuals. Of course, so do repeated impressions of the same ear, but studies indicate that there is discriminating value in the marks [4-7]. Interestingly, in light of Dallagher, another study suggests that DNA recovered from earmarks can produce false exclusions. When DNA in "60 earprints collected from three healthy adult volunteers under controlled laboratory conditions" was analyzed, "high levels of non-donor alleles [were] observed" [8]. (This is from the abstract of the study. I have not had time to read the body of the paper or check for follow-up work.)

It seems clear, however, that reports like the one in Der Spiegel unconditionally praising the power of "unique prints" cannot be reconciled with the research to date. Fortunately, the German police in the case against the 33-year-old Macedonian linked to some 100 robberies have more to go on than the man's ears. A Hamburg police spokeswoman also referred to fingerprints and DNA [9].

References

1. German Police Identify Burglar by His Earprints: Ninety-Six Break-Ins Solved, Spiegel Online Int'l, April 30, 2012, http://www.spiegel.de/international/zeitgeist/0,1518,830659,00.html
2. David Bamber, Prisoners to Appeal as Unique 'Earprint' Evidence Is Discredited, The Telegraph, Dec 2, 2001
3. Sean O'Neill, Expert Evidence Flaws Clear 'Earprint Killer', Telegraph, Jan. 23, 2004
4. Cornelis Van Der Lugt, Andrew Thean, Lynn Meijerman, & George J. R. Maat, Earprints, in Forensic Human Identification: An Introduction 73-84 (Sue Black & Tim Thompson eds. 2006)
5. Lynn Meijerman, Andrew Thean & George Maat, 1 Forensic Science, Medicine, and Pathology 247-256 (2005)
6. Ivo Alberink & Arnout Ruifrok, Performance of the FearID Earprint Identification System, 166 Forensic Sci. Int'l 145–154 (2007)
7. Ivo Alberink & Arnout Ruifrok, Repeatability and Reproducibility of Earprint Acquisition, 53 J. Forensic Sci. 325-330 (2008)
8. E.A. Graham, V.L. Bowyer, V.J. Martin & G.N. Rutty, Investigation into the Usefulness of DNA Profiling of Earprints, 47 Sci. & Justice 155-159 (2007)
9. Andy Eckardt, Earprints Allow German Cops to Nab Alleged Serial Burglar, World News on MSNBC.com, Apr. 30, 2012

Acknowledgments

Thanks to Ira Ellman and ASU student Seth Reeker for the link to the Der Spiegel article. Cross-posted to the Double Helix Law blog.

Why Can't Maryland Continue to Check Arrestee DNA Profiles?

In the wake of Maryland’s peculiar decision this week holding its arrestee DNA database law unconstitutional “as applied” (King v. State 2012), the Balitmore Sun reported that “a bank of nearly 16,000 DNA samples collected since January 2009 will remain in limbo. The samples were run through a database of cold-case evidence for matches” (Wenger, 2012). Presumably, this means that 16,000 DNA samples in the state’s possession (1) come from arrestees who have not been convicted (at least, not yet); (2) these samples already have yielded DNA profiles (digital records of DNA features used in making identifications); (3) the profiles are in a computer database that allows them to be searched against the profiles recovered from crime scenes or victims (in hot and cold cases, new ones and old ones, alike); but (4) the state has chosen to stop using the existing arrestee database. Thus, the Sun quotes a state police spokesman as saying that "The DNA database will remain inactive and the searching of any information in it ceased today" (Ibid.).

But why? Let’s assume that the King case was correctly decided — something that is not apparent from the reasoning given in the opinion and the cases cited there (Kaye, in press). It seems clear that trawling the crime-scene database for a match to an arrestee is not a search under the Fourth Amendment. Trawling and retrawling does not invade bodily integrity; neither does it reveal facts about the individual’s genome that are not already known. These are the only two interests that the Maryland judges in the majority provided as the basis for their opinion. The only interest that the database trawl implicates is the interest in not being tied to a crime-scene. Under rulings of the U.S. Supreme Court, a suspect’s bare desire not to be linked to a crime does not create a “reasonable expectation of privacy” (e.g., United States v. Jacobsen 1984). Government action that invades no reasonable expectation — in this case, retrawling — does not constitute a “search or seizure.” It is outside the scope of the Fourth Amendment.

But even if retrawling cannot constitute a search — a conclusion that has clear support in federal case law (Boroian v. Mueller 2010; Kaye 2011) — what about the illegality (according to King) in acquiring the DNA before the suspect has been convicted?  Does not the use of the illegally acquired and profiled DNA taint any hit made in the later trawl?  Is not the hit “the fruit of the poisonous tree,” as the courts call it, that must be excluded as evidence in a criminal case?

The answer could be “yes but no.” Yes, the trawl is the fruit and normally would have to be excluded from the state’s case in chief. Here, however, the illegal search (and its fruits) need not be excluded as evidence under the Supreme Court’s holding in Illinois v. Krull, 480 U.S. 340 (1987). Krull holds that the exclusionary rule does not apply when police conduct a warrantless, suspicionless, administrative search pursuant to a state law that later is found to be unconstitutional. That is precisely the situation here. The only “search” was the acquisition of the DNA for databasing, and it was conducted in good faith on the basis of a statute that seemed to be constitutional.

But surely this is too clever a legal argument. The good-faith exception supports (1) the acquisition of the DNA sample; (2) the laboratory analysis; and (3) all trawls conducted before the opinion in King. (So does the Supreme Court’s approach to the retroactivity of constitutional decisions.) This means that the lower courts on remand should uphold King’s original conviction, but retrawling after the court has ruled that the samples and profiles should not have been acquired goes beyond the situation in Krull. In that case, the police did no more than turn over the evidence they collected in good faith to the prosecution.

Thus, Maryland’s decision to keep the arrestee DNA database under wraps (at least until the Supreme Court rules on the practice or the Maryland court reconsiders the issue at some later time) is probably correct. But King should have no effect on “12 pending cases across Maryland that depend on such DNA evidence” or on the “65 arrests and . . . 34 convictions” (Wenger 2012) already obtained in good faith. Even if the five judges in the majority in King are right about the constitutional status of the law, the exclusionary rule does not apply to this previously acquired evidence.

References

• United States v. Jacobsen, 466 U.S. 109 (1984)
• Boroian v. Mueller, 616 F.3d 60 (1st Cir. 2010)
• King v. State, No. 68, 2012 WL 1392636 (Md. Apr. 24, 2012)
• David H. Kaye, A Fourth Amendment Theory for Arrestee DNA and Other Biometric Databases, 15 U. Pa. J. Const. L (in press)
• David H. Kaye, DNA Database Trawls and the Definition of a Search in Boroian v. Miller, 97 Va. L. Rev. in Brief 41 (2011)
• Yvonne Wenger, Md. Authorities Stop Post-arrest DNA Collection: Sampling Halted Pending Potential Supreme Court Appeal, Baltimore Sun, Apr. 27, 2012

Maryland's Highest Court's Opinion on Arrestee DNA Is an Outlier

Maryland's highest court is its Court of Appeals. Two days ago, in King v. State [1], this court became the first supreme court of any state to hold that taking a DNA sample from an arrestee is unconstitutional. But you would not know this from the court's opinion.

Instead, the Maryland court purports to follow "the Minnesota Supreme Court in C.T.L." Considering that the Minnesota Supreme Court did not decide C.T.L. and that it has yet to consider the routine practice of taking DNA prior to arrest [2], this is no small feat.

The majority opinion in King, penned by Judge Glenn T. Harrell, Jr., contains additional gaffes. It refers to Judge Marjorie Rendell of the U.S. Court of Appeals for the Third Circuit as a man, and it asserts that "Fourth Amendment analyses" are "more stringent" than "a First Amendment 'rational basis' review" -- whatever that may mean.

Of course, these infelicities do not mean that the opinion is wrong -- although it is long on description and short on analysis. The balancing of state and individual interests that is pivotal to the opinion is less than lucid. We can get a sense of the court's approach from its discussion of the individual interests that the opinion seeks to protect. To begin with, the Maryland court gives more weight than other courts do to the interest in being free from an unwanted but painless and relatively minor intrusion into one's body. Judge Harrell writes that DNA

is collected by swabbing the interior of a cheek (or blood draw or otherwise obtained biological material). While the physical intrusion of a buccal swab is deemed minimal, it remains distinct from a fingerprint. We must consider that “[t]he importance of informed, detached and deliberate determinations of the issue whether or not to invade another's body in search of evidence of guilt is indisputable and great.” Schmerber, 384 U.S. at 770.

The puzzle here is that, if the physical intrusion is indeed minimal, why is it of “great importance” to have a “detached . . . determination” in the form of a judicial warrant? It cannot be the peculiar notion that laboratory analysis to produce an identifying profile is a separate search requiring a warrant. If that were so, the laboratory analysis of “abandoned” DNA of a suspect also would require a warrant. This might be a reasonable position—but the King court does not retreat from State v. Williamson, 993 A.2d 626 (Md. 2010). There, the police recovered and then analyzed DNA from a drinking cup given to a suspect at a police station, and the Maryland Court Appeals flatly rejected the separate-search argument. Furthermore, if the “physical invasion” aspect of the DNA collection were of such great importance, the state could avoid the impact of King by changing the method for collecting the DNA. Instead of a buccal swab, the arrestee could be asked to place his fingers on a sticky pad to which some cells would adhere.

The interest that actually seems to be driving the opinion is not that the arrestee is compelled open his mouth so that some cells can be scraped from the inside of his cheek. It is, in the King court's words, the possibility that “the vast genetic treasure map that remains in the DNA sample retained by the State” will be read or released in violation of state law. But the opinion utterly fails to address whether the state’s possession of that unread map (the physical sample kept under lock and key) unreasonably interferes with a defined privacy interest. And even if it does, could not Maryland acquire the identification profiles -- data that are nothing like "[a] person's entire genetic makeup and history" -- and then destroy the physical sample to satisfy the court's oddly applied balancing test?

Despite its problems, both superficial and fundamental, King is not devoid of all redeeming value. For example, the court correctly distinguishes between the use of a biometric identifier for identification and its use of it for intelligence purposes. But the opinion sheds no new light on the constitutional issue and casts some grotesque shadows. Readers seeking a deeper analysis will have to look elsewhere [3].

References

1. King v. State, No. 68, 2012 WL 1392636 (Md. Apr. 24, 2012)
2. In re Welfare of C.T.L., 722 N.W.2d 484 (Minn. Ct. App. 2006)
3. David H. Kaye, A Fourth Amendment Theory for Arrestee DNA and Other Biometric Databases, University of Pennsylvania Journal of Constitutional Law, Vol. 15 (in press)

Postscript

Alan Lazerow pointed out that the court's opinion does not have the superficial flaws that caused my jaw to drop and pen to move. Thankfully, the opinion as now posted on Maryland's website and Westlaw have these blemishes removed.

Cross-posted to the Double Helix Law Blog.

Who is Nelson Acosta-Roque? (Part I)

According to the Department of Homeland Security, he is Victor Antonio Pecheca-Aromboles, an old cocaine dealer born in the Dominican Republic who served time in Pennsylvania in the early 1990s, was deported, and came back to the U.S. under an alias (via Puerto Rico, where he lived illegally for a few years), ending up in Anchorage as a waiter in a brew pub for the last ten years. [1] On the basis of a comparison of copies of fingerprint cards from Pennsylvania (for Pecheca-Aramboles) and New Jersey, Puerto Rico and Alaska (for Acosta-Roque), the government convinced the immigration judge and the Board of Immigration Appeals that the Anchorage waiter is the former Pennsylvania cocaine dealer.
The removal order is before the Ninth Circuit Court of Appeals. According to law professor Caleb Mason, who represents Acosta-Roque, the “the only question is the weight of an alleged 8-point match: is that enough, standing on its own, to warrant a finding of identity by clear and convincing evidence?” [1] To address this question, Professor Mason enlisted the aid of 39 “Scientists and Scholars of Fingerprint Identification as Amici Curiae” to file a brief in support of his client. The brief, which was written by Simon Cole of the University of California at Irvine, describes the expert’s testimony as problematic, unjustified, inadequately supported, vague, and groundless. [2]
My reading of the transcript, however, suggests that the issue on appeal is not really whether “an alleged 8-point match” is enough. The four ten-print cards were compared by Susan R. Blei, the supervisor of Alaska’s Criminal Records and Identification Bureau. Ms. Blei’s qualifications consisted of about seven weeks of training courses over the years, many “educational conferences” on AFIS (the Automated Fingerprint Identification System) organized by NEC, and many years of on-the-job experience. She never testified that there was a match at exactly eight points of comparison. She testified that she likes to have at least eight points before signing off on an identification, but she did not give the number of features on which she relied to form her “100% certain” opinion that all the ten-print cards came from one and the same individual. In essence, she said, “I compared, I counted, I concluded (and so did my unnamed verifying examiner).” She provided this ipse dixit with the encouragement of the government’s counsel. Thus, the issue should be whether the opinion of a fingerprint examiner, presented in this conclusory, “trust-me” fashion, can amount to clear and convincing evidence—the standard the government has to meet to establish that Acosta-Roque obtained his permanent resident status fraudulently, having been deported under a different name.
Is a fingerprint analyst’s assertion of identity clear and convincing proof when it lacks any meaningful description of the process, when it contains no statements that would show that the examiner followed accepted protocols (beyond the fact that the examiner took some short courses and has years of experience), and does not indicate the examiner’s performance on rigorous tests of her proficiency? There is at least a decent argument that it does not.
Related questions are whether the “trust me” testimony in this case met professional and ethical standards and whether existing scientific research warrants the claim of 100% certainty. I shall comment on some aspects of these questions, and on the positions of the “scientists and scholars of fingerprint identification,” in later postings.
References
1. Caleb Mason, Scientific Validity of Fingerprint Comparison: New Case and Amicus Brief (Mar. 5, 2012), http://prawfsblawg.blogs.com/prawfsblawg/2012/03/scientific-validity-of-fingerprint-comparison-new-case-and-amicus-brief.html.
2. Brief of Scientists and Scholars of Fingerprint Identification as Amici Curiae in Support of Petitioner and in Favor of Reversal, Acosta-Roque v. Holder, No. 11-70705 (9th Cir., Mar. 8, 2012).

Latent Fingeprint Identification for a New Generation: The NIST Report

Last month, after three-and-one-half years of seemingly interminable meetings, the Law Enforcement Standards Office at NIST (the National Institute of Standards and Technology) released a comprehensive report on improving the practice of latent print examination for criminal identification. It can be downloaded as one big pdf file. My views are not those of an objective observer (I was the editor and an author of the report), but I can say with 100% confidence that the book should be of interest to lawyers who encounter fingerprint evidence, not to mention all fingerprint analysts and many other individuals concerned with the production and delivery of forensic science evidence.

The oversized working group included both “insiders” (fingerprint examiners and representatives of professional organizations) and “outsiders” (psychologists, statisticians, engineers, law professors, etc.). Like most expert groups charged with making scientific assessments and recommendations for best practices, the group did not conduct new research, but it reviewed and described a substantial body of existing work in the forensic sciences, cognitive science, human factors, and law.

The group was hardly unanimous on every issue, but it succeeded in addressing the larger issues that have been prominent in the modern literature and cases on fingerprint identification — issues such as the measurement of error rates in fingerprint examinations, the role of statistical and intuitive methods in drawing inferences about identity, the scientific foundations of the discipline, and the ethical and legal considerations in reporting and testifying about laboratory findings.

One suggestion in the report regarding the last item is that the fingerprint community needs to be open to rethinking its historical postulates about what “identification” means and should adopt more cautious ways of describing the implications of similarities in latent and exemplar prints. Thus, a summary paragraph notes that

[W]ays to describe the possible association include statements about the strength of the evidence (the likelihoods) or the posterior probability. With appropriate data and validated modeling, such statements could be quantitative . . . , but less precise qualitative descriptions of the strength of the evidence or the source probability also are possible. . . . Given the current state of scientific and professional knowledge, . . . it is best to avoid testimony based on the theory of global general uniqueness. [E]xaminers [should] not testify to an identification to the exclusion of all other individuals in the world, [and] other, more conservative methods for conveying the probative value of a match [are available]. . . . The Working Group did not reach a consensus on which of these alternatives to universal-individualization testimony is best.

The alternatives listed in the report do not include statements like "it is a practical certainty that the prints are from the same finger." They do include the more radical suggestion that experts should avoid source attributions in favor of statements about "likelihoods." This a bit of statistical jargon that I won't take the time to explain here. The book contains a sample laboratory report that presents an example of the strength-of-the-evidence approach.

Reference

Expert Working Group on Human Factors in Latent Print Analysis, NIST, Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach: The Report of the Expert Working Group on Human Factors in Latent Print Analysis (David H. Kaye ed. 2012), available at http://www.nist.gov/customcf/get_pdf.cfm?pub_id=910745