Inside the Cell: The Dark Side of Forensic DNA

Abstract

In recent years, several forms of previously accepted forensic science have come under scrutiny as unreliable or simply unsound.1 For instance, the science of arson investigation is among ‘the most prominent current example[s] of shifted science potentially calling into question hundreds or thousands of convictions that occurred over the past few decades’.2 The National Academies of Science (‘NAS’), in a 2009 report on forensic science, observed that there is a paucity of research supporting forensic arson investigation.3 The report also concluded that ‘many of the rules of thumb that are typically assumed to indicate that an accelerant was used (e.g., ‘alligatoring’ of wood, specific char patterns) have been shown not to be true’.4 Bite mark analysis raised similar concerns. The NAS report observed that ‘[a]lthough the majority of forensic odontologists are satisfied that bite marks can demonstrate sufficient detail for positive identification, no scientific studies support this assessment, and no large population studies have been conducted. In numerous instances, experts diverge widely in their evaluations of the same bite mark evidence’.5 More recently, the Texas Forensic Science Commission recommended a moratorium on bite mark evidence in criminal trials.6 The FBI itself has questioned or discontinued use of forensic methods including bullet lead examination7 and hair analysis8 in light of evidence that such methods are not probative or are simply unsound. With respect to hair analysis, ‘[t]he Justice Department and FBI…formally acknowledged that nearly every examiner in [the FBI Laboratory's microscopic hair comparison unit] gave flawed testimony in almost all trials in which they offered evidence against criminal defendants over more than a two-decade period before 2000’.9 Not even fingerprint analysis has escaped unscathed. Here, too, the NAS report noted a lack of scientific evidence supporting the accuracy of modern fingerprint analysis.10 The report also expressed concern about the dearth of information (or disclosure thereof) of error rates in such analysis, concluding that ‘[a]lthough there is limited information about the accuracy and reliability of friction ridge analyses, claims that these analyses have zero error rates are not scientifically plausible’.11 By comparison, DNA analysis has typically been viewed ‘like a crystal ball being handed to the criminal justice system’.12 The same NAS report that castigated so many traditional forensic sciences lauded DNA analysis as a forensic discipline with high ‘probative power’.13 Indeed, the report took DNA analysis as a point of comparison for other forensic sciences. Unlike toolmark and firearms analysis, for instance, ‘the protocols for DNA analysis do represent a precisely specified, and scientifically justified, series of steps that lead to results with well-characterized confidence limits, and that is the goal for all the methods of forensic science’.14 Forensic DNA analysis deserves much of the acclaim it has received. It is, as the NAS report observed, ‘scientifically sound’, and its development was ‘a fortuitous by-product of cutting-edge science’.15 But not all is well in the realm of forensic DNA analysis. In her new book, ‘Inside the Cell’, Erin Murphy complicates the laudatory tale of forensic DNA analysis, warning that ‘the same forces that corrupted other, older forensic methods still remain very much alive in the criminal justice system today’.16 Murphy examines how DNA is collected, analyzed, disclosed, and used in criminal investigations and in courts, exposing both the promise and documented pitfalls of DNA analysis in each arena, as well as how these matters are intertwined and interdependent. She exhorts readers that ‘DNA testing is neither savior nor cure-all: it is just another form of proof deserving of careful attention’.17 Ultimately, Murphy concludes that ‘we must attend to issues surrounding efficiency, accountability, accuracy, privacy, and equality’ in order to ‘fairly and accurately harness the power of forensic DNA testing’.18 Despite the power and breadth of Murphy's final analysis, there is one issue that unfortunately goes unnamed: transparency. Concerns about transparency surface at various points in Murphy's analysis, from cover-ups of lab errors,19 to non-disclosure of state or laboratory policies regarding when, how, and for how long DNA samples may be used,20 to refusals by developers of DNA testing software to share their source code with defendants.21 Yet, when Murphy's final chapter focuses on tying together the seemingly disparate strands of her analysis, transparency is not among those values she names as most important. To be sure, Murphy identifies transparency as important to achieving some of her named values, including accountability22 and accuracy.23 But transparency is more than merely instrumentally important; it is itself of sufficient significance that its absence from Murphy's ‘road to reform’ is striking. This is, however, a small quibble with an otherwise invaluable resource for those interested in the rapidly expanding world of forensic DNA analysis, and in the relationship between science and law enforcement more broadly. ‘Inside the Cell’ divides its focus into four parts, the last of which sets out Murphy's proposal for ‘building a better DNA policy’.24 After a brief overview of DNA science and forensic typing, Murphy first examines how the ‘popular understanding of forensic DNA testing’—as a crisp, objective, near infallible science—fails to reflect the much murkier facts of real life.25 Experts in the field have long known that ‘interpretation of DNA from crime scenes can be incredibly complex’.26 But the various ways in which that complexity arises and may be compounded are growing. In one recent study, researchers asked 17 experienced DNA examiners to analyze a DNA mixture (a sample including DNA from more than one person) from an alleged gang rape; the examiners reached widely divergent conclusions about whether a particular suspect might have been involved in the rape.27 What is more, only one of the 17 examiners tendered a conclusion consistent with the analyst in the actual case in which the DNA mixture arose—a conclusion introduced at trial to convict a real-life suspect of the crime.28 These divergent conclusions are possible, even for a well-grounded scientific endeavor like forensic DNA typing, because the DNA collected at real crime scenes is often unlike the pristine DNA samples that we provide to our doctors or that known arrestees and convicted persons provide through a cheek swab. Unlike samples taken in a controlled environment, ‘crime scene testing…is like seeking results from [a] dirty Band-Aid—after it has been in the trash for two weeks’.29 Such samples ‘may have been exposed to light, heat, moisture, or chemicals that can compromise the ability to get results’.30 A sample may also contain DNA from an unknown number of persons,31 not all of whom may have had direct contact with the tested object at all or contact in proportion to the number of their cells on the tested object.32 Each of these complicating factors may be further compounded by recent extensions of forensic DNA analysis to so-called ‘touch’ DNA or ‘low copy number’ settings—those in which DNA analysis is performed on a very small number of cells or even a single cell.33 As Murphy explains, in these settings ‘the rules of thumb that help analysts interpret ordinary samples do not work as well…, and guided subjectivity risks becoming little more than self-justifying guesses’.34 Yet, of the few courts to adjudicate the admissibility of low copy number test results, most have deferred to prosecutors' assertions that such testing is just like ordinary forensic DNA analysis.35 Meanwhile, laboratories engaged in this envelope-pushing testing have frequently ‘refused to disclose the protocols and studies’ informing their analysis, claiming that this information is proprietary.36 These difficulties may be present even if the crime scene investigators, lab analysts, and everyone in between perform their jobs flawlessly. But this is an unrealistic assumption. As Murphy documents, there are now dozens of known (and how many more still unknown?) scandals involving sloppy, mistaken, or fraudulent casework.37 All the while, forensic analysts decline or refuse to disclose error rates when reporting DNA match probabilities in court, perpetuating the notion that forensic DNA analysis is free from either scientific or human error.38 Having enumerated how the processes for generating a DNA profile can mislead or give rise to error, Murphy casts her perspective more broadly, examining how the search for and report of forensic matches can similarly mislead jurors, judges, prosecutors, and even lab analysts. Different ways of calculating DNA match probabilities may give rise to widely divergent statistics and very different levels of certainty that a particular suspect or defendant ‘did it’.39 There are at least 10 different software packages on the market for decoding whether a particular suspect or defendant's DNA is present in a complex sample, like a mixture or low-quantity crime scene stain—each utilizing its own algorithm.40 Meanwhile, the FBI prohibited database research that threatened to complicate the one-in-several-trillion type of statistics on which prosecutors routinely rely in court.41 While differing statistical models and disagreements about whether a DNA match has been found would be inconvenient in a case in which DNA were just one piece of evidence against the defendant, these matters take on increased significance in the growing number of cases prosecuted based on a DNA match alone.42 Murphy also trains her attention on the new and expanding ways investigators are using DNA samples, profiles, and databases to identify suspects and bring prosecutions. Analysts have played ‘Go Fish’ with the national database, uploading variations of an unclear profile in hopes that one of them will yield a match.43 Labs have also erroneously uploaded DNA profiles from individuals who do not meet the requirements for database inclusion, including victims.44 And labs and new private vendors are now experimenting with ‘forensic DNA phenotyping’—creating a ‘genetic mugshot’ of the perpetrator of a crime based on the DNA he left behind at the crime scene.45 To date, forensic DNA typing has focused on portions of DNA not known to have any useful function (other than their use for forensic typing).46 DNA phenotyping relies on entirely distinct portions of the genome.47 The range of individuals subject to perpetual genetic surveillance has expanded in other ways as well, often with judicial blessing. States have consistently expanded the reach of offender DNA databases beyond those convicted of serious felonies.48 Today, nearly all states require those convicted of any felony to provide a DNA sample, most require a sample from those convicted of certain or any misdemeanors, and a growing number compel DNA samples from those merely arrested for a felony or misdemeanor.49 In Maryland v. King, the Supreme Court expressly sanctioned arrestee sampling.50 Courts have also largely held that the DNA we involuntarily and unknowingly leave behind in our ordinary activities—licking a stamp, sipping from a glass, visiting a doctor for a routine pap smear, discarding a pizza slice—has no protection from police collection and analysis for any purpose.51 Such surreptitious sampling gives rise to wholly unregulated sources of DNA for analysis.52 When the profiles from these kinds of samples do not meet the FBI's requirements for inclusion in the federally-regulated databases, labs often maintain them in off-books ‘rogue’ databases free from oversight and unburdened by the limited uses for which the federally regulated databases may be used.53 Laboratories have introduced and expanded the use of existing samples through familial searching as well. Familial searching, or the use more generally of partial matches, proceeds from a close-but-imperfect match between a crime scene sample and a known offender profile to launch an investigation into that known offender's close genetic relatives.54 Familial searching describes an intentional database search for these kinds of close matches; partial matching more broadly embraces instances in which such matches are fortuitously discovered during routine databases searches.55 Whether fortuitous or deliberate, partial matching takes advantage of the biological fact that close genetic relatives are more genetically similar than unrelated individuals to effectively sweep the relatives of known offenders into the database—even when those relatives have never been arrested or convicted of a offense enabling their direct inclusion in the database.56 Because the existing offender databases reflect the racial disparities of the criminal justice system writ large, moreover, the burdens of expanded DNA collection, testing, and use fall more heavily on racial minorities.57 Murphy finally brings these myriad strands of DNA difficulties together, identifying shared themes and interdependencies between lab, lawyer, and law. Murphy reminds readers, ‘it is a mistake to think that [forensic DNA testing's] underlying scientific legitimacy will, on its own, ensure the integrity of DNA evidence’.58 Murphy calls for ‘broad systemic reform’, attending to ‘issues surrounding efficiency, accountability, accuracy, privacy, and equality’, in order to ‘fairly and accurately harness the power of forensic DNA testing’.59 While Murphy does tremendous work in bringing together multiple strands of analysis of the scientific and legal challenges of forensic DNA testing, one issue crucial to the fair and accurate use of forensic DNA testing remains underdeveloped: transparency. The need for greater transparency is one that arises at numerous points in Murphy's own analysis. Indeed, the disjunction between the perception of forensic DNA analysis as a pristine science and the reality of the difficulties associated with identifying DNA profiles from samples more ‘like dirty Band-Aids’ is itself a reflection of a lack of transparency about the realities of forensic DNA typing.60 That the former is a perception shared by the public,61 courts,62 and even the National Academies of Science63 is a testament to how far from transparent information about the true difficulties of DNA analysis has become. The refusal of laboratories to provide, and of courts to demand, evidence regarding error rates in DNA analysis both compounds this disjunction and is, similarly, evidence of a lack of transparency about how such analysis operates in practice.64 Inadequate oversight of quality control within forensics labs exacerbates these transparency gaps. As Murphy documents, ‘nearly every major DNA unit—from the most applauded and sophisticated to the most amateur and haphazard, has endured a scandal of some kind’.65 Yet, the lab personnel at fault often escape censure for years at a time and laboratories are rarely disciplined.66 Many state lab officials sweep issues regarding quality control ‘to the side’.67 Oversight mechanisms are rarely rigorous, encourage underreporting of errors even when inspections occur, and hardly ever report misfeasance in a publicly accessible way.68 One of the major accrediting bodies for crime labs fails to include even basic data about compliance on its website.69 Nor do transparency gaps mask only human error in forensic DNA analysis. Several software architects marketing and deploying software packages for testing complex mixtures, low-quality samples, or low-quantity samples have ‘refuse[d] to information about their source code or the in which their statistics are This is so the fact that these models different results, because they give to different In one the of one such software that no other had code or it all the to the source code and it as a Yet, the the software and its results to be into To the software to the prosecutors as their and testimony about the of The a transparency regarding the and use of the forensic DNA For one a growing number of labs have expanded the reach of state forensic databases through the use of partial DNA matches to investigation of the of a known While a of states have publicly policies in when and how they these kinds of matches, a greater number have policies the use of such partial matches that are in laboratory and were by lab personnel largely More data about how analysts use the and national DNA databases is to in light of FBI rules disclosure of information to such In many instances, those the lab and prosecutors will never even whether a database search more than one And lab analysts with prosecutors ‘Go Fish’ in DNA databases, are routinely to the databases to search for other to a The of DNA databases of the FBI's is rarely even publicly In these databases, analysts have DNA profiles from crime individuals DNA samples in to police or to as and individuals of police DNA has been collected from a object they have databases the reach of that either the or quality of the they As Murphy ‘the law effectively police to in the ways possible, by the least oversight and protection to DNA samples collected on the of transparency every issue Murphy in her Murphy to that transparency is to ‘fairly and accurately harness the power of forensic DNA To be sure, Murphy transparency to achieving some of her named under Murphy that ‘[t]he greater can only if it in with a greater Here, Murphy in to better oversight mechanisms for laboratory quality information about the results of such oversight must be more publicly Murphy also transparency to in calling for for and for the disclosure of the source code used to DNA match And under Murphy calls for information about how our DNA databases are identifying a range of about the and use of federally databases that would be to Yet, these of transparency that transparency is only as it and Murphy's named transparency in a supporting however, the important that transparency itself can in bringing about better and and have long that transparency is to the of the of privacy, acknowledged that as a for and is to be the of have and to has most to be to the through the in the More recently, as of the the which certain and to disclose their with and research the of transparency as In one study, researchers between an of and an of a of to an at a In such a individuals have the of into the to a there is no enforcement for The researchers found that as much in the with than with There was no evidence that type A when an of to was individuals were to in a In other of might is otherwise sufficient to more and may yield and better policies and A positive relationship between transparency and more is also in at least one of forensic DNA partial matching for familial In partial matching policies a lack of states that reporting of at least some partial matches, however, of greater transparency with policies that include more scientific and steps to The four states that have a partial match at least in the absence of a few to disclosure of those In states that have a to those policies to be not only to in most also more specific in their than their This is so for states both fortuitous and partial The policies in these states are more often publicly accessible and more only on the quality of the partial also on the of cases in which partial match information may be is not this limited between greater and greater that transparency may yield greater in This is not to that transparency and disclosure be mechanisms function both as and as As Murphy the of information about DNA is in the forensic DNA database is one such it more to and report accurate statistics about the database population and how its profiles are being But has the of also it more ‘to or with the greater transparency

Cite this work

No public copy is stored for this record, so only the metadata is cited.

Stored only when both papers are in the corpus — 38 citations exist upstream.

Papers that cite the same references — the relational fallback while embeddings are still backfilling.