The Rock Ethics Institute

Home > Initiatives > Bioethics > Resources > Selected Works > Genetics and Criminal Law: Ethical Considerations > Genetic Testing: Conclusiveness and Reliability


Genetic Testing: Conclusiveness and Reliability

  1. Conclusiveness and guilt:
    1. The common conception that DNA evidence is infallible, is simply not true ((17 ND J .L. Ethics & Pub Pol’y 269,271).  “DNA evidence can be conclusive only as to one factual issue”– that factual issue being “whether or not the evidence originated with the defendant” (17 ND J .L. Ethics & Pub Pol’y 269,280).  For example, “semen might be present on an alleged victim’s clothing or a bedsheet without occurrence of penetration, or it could be found in a vaginal swab despite consensual sex” (Id).   Thus, though DNA evidence can conclusively prove innocence, “it is not logically sufficient to prove guilt’” (Id, bold added).  It is vital that jurors and the public understand this difference – and ideally an accused party will have access to a competent attorney who can make this distinction clear.
  2. Accidents:
    1. Accidents do happen.  Some commentators have faith that “in instances where samples were mishandled, switched or otherwise contaminated before they reached the laboratory or during testing, ‘a defendant might succeed in raising a reasonable doubt about the reported results of the DNA tests” ((17 ND J .L. Ethics & Pub Pol’y 269,271, citing Edward J. Imwinkelried & D.H. Kaye, D.N.A. Typing: Emerging of Neglected Issues, 76 Wash. L. Rev. 413 (2001)).  But again, the individuals targeted for prosecution are also often indigent and they may not have the resources both financially and socially to effectively combat these wrongs.
    2. Raymond Easton and mistaken DNA identification:
      1. There are, in fact, cases where mistaken DNA identification has occurred.  The first reported case of mistaken DNA identification occurred in the UK.  In 1999, Raymond Easton, “a 49-year-old man living in Swindon in the advanced stages of Parkinson's disease, was charged with a burglary in Bolton 200 miles away. Even though he could barely dress himself, he was still arrested” (
        ).  Easton had provided a DNA sample to the police several years earlier following a domestic dispute, and that sample had remained within the DNA database.  During trial, it was stated that, “[t]he odds of the arrestee’s DNA being wrongly matched against that of the crime scene were said to be one in 37 million” (  The first test involved the examination of 6 loci – but when the DNA was then examined again at the request of Easton’s solicitor, using a retest involving 10 loci the results “showed an exclusion at the additional four loci” – thus exonerating Easton from the crime (Id).
      2. Furthermore, despite the fact that the prosecution stated that the odds of the DNA being wrongly matched were 37 million to one:  “It should be understood that that calculated frequency is an estimate, and can be off by an order of magnitude in either direction…. In other words, despite the statistical calculation of 1 in 37 million on six loci, that does NOT mean that the six loci cannot match more than one person in 37 million.  According to population geneticists, it is indeed possible to have the six loci match in perhaps many dozens of individuals whose DNA is contained in a databank of 700,000” ( 
    3. Typographical Errors:
      1. More rudimentary errors have occurred in DNA labs as well, thus presenting inaccurate results.  In 2002, an audit of the Las Vegas Metro Police’s DNA lab found “a typographical error that wrongfully accused a man of two rapes”
        ).  Lazaro Sotolusson's name was placed on another man’s DNA information which, when placed in a placed in a computer database, matched that of two unsolved rape cases.   Lazaro was “charged for multiple felonies, including sexual assault and first-degree kidnapping in connection with the assaults on the two juveniles”
        (  In the preliminary hearing, one of the female victims identified Sotolusson as the perpetrator, and “authorities said the DNA evidence indicated the odds that Sotolusson was not the offender were 1 in 600 billion” (Id).  Sotolusson was jailed for approximately one year while awaiting trial (Id).  The Clark County Public Defender Office, which had attorneys representing Sotolusson, hired their own forensic scientist, Norah Rudin, who discovered the clerical errors (Id).  One of the attorneys working on the case, Brigid Hoffman, noted “We were lucky the public defender had the resources to hire an expert as good as Norah Rudin” (Id). (*Link to (III)(b))
    4. Switched samples:
      1. Other errors involving the switching of genetic samples have “led to false incrimination in rape cases in Philadelphia and San Diego”  A list of cases involving forensic DNA errors, along with transcripts of court testimony can be accessed at the following site:
      2. In 1993, a jury in Tulsa Oklahoma convicted Timothy Durham for sexually assaulting a juvenile and he was sentenced to 3000 years in prison 
        (  Although Durham had been able to provide 11 alibi witnesses who were able to place Durham in a different state on the date and time of the attack, the state prosecuted its case “almost entirely on a DNA test, which showed that Durham’s genotype matched that of the semen donor” (Id).  Durham’s post-conviction DNA testing, however, “showed that he did not share the DQ-alpha genotype found in the semen,” and “he was also excluded at several other genetic loci in multiple tests” 
        (  The error that occurred in the initial forensic analysis was one of “misinterpretation” (Id).  The laboratory had failed to fully separate “the male and female DNA from the semen stain, and the combination of alleles from the two sources produced a genotype that could have included Durham’s” 
        (  Durham served 4 years in prison before being released in 1997 (Id).
  3. Innocence Protection Act:
    1. In the future, the availability of resources for post-conviction DNA testing might become more accessible.  The Innocence Protection Act (IPA) of 2003 was introduced in the 107th Congress on October 1, 2003, as a component of a larger bill called the Advancing Justice Through DNA Technology Act (HR 3214) 
      ( This bill would “grant any inmate convicted of a federal crime the right to petition a federal court for DNA testing to support a claim of innocence. It also encourages states - with the power of the purse - to adopt adequate measures to preserve evidence and make postconviction DNA testing available to inmates seeking to prove their innocence” (Id).
      1. In November, 2003, the Advancing Justice Through DNA Technology Act (HR 3214) passed the House of Representatives with a vote of 357-67 and is “presently pending before the Senate” 
    2. Kirk Bloodsworth:
      1. The IPA would “establish the Kirk Bloodsworth Postconviction DNA Testing Program, which would provide $25 million to help states defray the costs of post-conviction DNA testing under the act” (  This program “is named after Innocence Project client Kirk Bloodsworth, who, in 1993, became the first death row inmate in the nation to be exonerated by post-conviction DNA testing” (Id).
  4. Operator Bias, Incompetence: 
    1. Josiah Sutton, and the Houston Police Crime Laboratory:
      1. There are also cases where errors in the analysis of the DNA are the result of incompetence and misrepresentation.  In 1999, then 16 year old Josiah Sutton “was convicted of rape based largely on DNA tests performed by the Houston Police Crime Laboratory.” 
        ).  Sutton was in prison for over 4 years, when his case was analyzed by reporters from Houston television station KHOU, who were investigating rumors that “had circulated for years about bad work by the HPD crime laboratory.”  
        ).   The reporters contacted Professor William Thompson of the Department of Criminology, Law & Society at the University of California, Irvine, Thomspon, who has worked on issues of forensic DNA evidence for over 15 years (Id).  Thompson uncovered the error by using more sophisticated testing methods than those employed by the Houston Police Crime Lab, and the results exculpated Sutton from having committing the crime (Id).  But according to Thompson, the prosecutor and the laboratory additionally “misrepresented the DNA evidence in several respects” (Id).  Thompson stated: “The testimony left the impression that the DNA evidence uniquely and definitively identified Sutton as one of the rapists….  If police picked any two black men off the street, the chances that one of them would have a DNA profile that ‘matched’ the semen sample as well as Sutton’s profile is better than one in eight” (
    2. Administrative culture at Houston PCL:
      1. Even more problematic was the finding that the problems in the laboratory were not merely the accident of one careless analyst, but were instead administratively widespread.  According to Thompson, “the laboratory failed to run essential scientific controls, failed to document their work adequately, and engaged in a variety of practices that were create a risk of error,” (
        ).    Furthermore, the analysts were consistently overstating the statistical significance of their findings in both written reports and in courtroom testimony (Id).  Thompson additionally stated that:
      2. “In at least two instances the laboratory reports appeared to be inconsistent with the underlying scientific data.  It appeared that DNA analysts were stretching and distorting their findings to help get a conviction” 
        , emphasis added). 
      3. As a result of this investigation and the allegations made against the Houston Police Crime Laboratory, the DNA section of the HPC Lab was audited in December of 2002 (  The audit, which confirmed Thompson’s findings, subsequently caused police officials to suspend DNA testing at the lab (
        Crime%20 Lab%20Faces%20Scrutiny.htm
        ). 369 samples of DNA previously analyzed by the HPC Lab were to undergo retesting at independent laboratories; but, “evidence in more than 20 cases slated for DNA retesting is missing, the Houston Police Department said Monday [November 3, 2003], giving few other details” (
        ).  However, as of December 18, 2003, approximately 1/3 of the retesting (128 or 369 samples) had been completed (
        ).  The results obtained “by three private labs have confirmed police analysis in a majority of the cases,” however, “additional retesting is under way in about two dozen cases returned thus far” (Id).
    3. Operator bias:
      1. Some of the errors involved in the Houston Police Crime Laboratory scandal seem to have been influenced by operator bias (*Link to (IV)(d)(ii)(2)*).  Although “current DNA tests rely heavily on computer-automated equipment, the interpretation of the results often requires subjective judgment” (
        ).  Consequently, in situations where the results are not entirely dispositive, the prejudices of analysts can improperly weigh into their interpretation of the evidence (Id).
    4. Observer Effects:
      1. Although operator bias is sometimes conscious and intentional, it is perhaps less pervasive than errors arising from “observer effects.”   The study of observer effects is based on a fundamental “principle of modern psychology” which claims that “the desires and expectations people possess influence their perceptions and interpretations of what they observe” (D. Michael Risinger, Michael J. Saks, et. al., 90 Cal. L. Rev. 1, 6 (2002)).  Studies in modern psychology have shown that suggestion can be powerful in shaping an individual’s expectation of what the truth should be.  Unfortunately, sometimes forensic scientists simply “refuse to take appropriate steps to "blind" themselves to the government's expected (or desired) outcome when interpreting test results” (
        ).  In some ways, however, this is an understandable position, as it is standard practice among many within law enforcement to provide “domain-irrelevant” information to forensic analysts (D. Michael Risinger, Michael J. Saks, et. al., 90 Cal. L. Rev. 1, 33 (2002)). 
      2. Lab notes:
        1. Consequently, some analysts are, indeed, influenced in ways that compromise their ability to objectively assess the scientific information.  The effects of this improper influence are sometimes evident in lab notes, when analysts have written comments regarding the case that are irrelevant and likely prejudicial regarding the genetic testing (
          ).  For example:
        2. A forensic scientist, involved in analyzing the DNA of a particular case wrote: "Suspect-known crip gang member — keeps 'skating' on charges-never serves time. This robbery he gets hit in head with bar stool — left blood trail. [Detective] Miller wants to connect this guy to scene w/DNA …" ” (D. Michael Risinger, Michael J. Saks, William C. Thompson, & Robert Rosenthal, The Daubert/Kumho Implications of Observer Effects in Forensic Science: Hidden Problems of Expectation and Suggestion. 90 Cal.L.Rev. 1, 36, FN 165 (2002))). 
        3. In a separate case, where the defense attorney “had suggested that another individual besides the defendant had been involved in the crime, and might have left DNA, the DNA laboratory notes include the notation: ‘Death penalty case. Need to eliminate [other individual] as a possible suspect.’" 
        4. Unfortunately, according to some commentators, “such cases are by no means uncommon” (Risinger, Saks, et al., 90 Cal.L.Rev. 1, 37 (2002)). 
      3. Safeguards:
        1. Some argue that with an appropriate number of safeguards, such as a three tiered-system of peer review, the likelihood of compromising the validity of the forensic information would be minimized.  Many DNA testing laboratories presently do have peer review involving multiple scientists – but even in these situations, there have been documented problems with “conformity effects,” where people agree with the generalized opinion to be “in step with their peers”  ” (Risinger, Saks, et al., 90 Cal.L.Rev. 1, 19 (2002)).  In addition, greater safeguards mean greater costs in terms of time, work, and money involved – but as “virtually all other fields of science have determined that the risk of harm due to observer effects is so great, and the need for valid findings is so important, that the increased costs are worth paying in order to gain the benefits that proper testing procedures bring” (Risinger, Saks, et al., 90 Cal.L.Rev. 1, 52 (2002)).  At very least, the possibility for standards incorporating blind testing and evidence line-ups (where there are multiple specimens, some of which are “foils”) should be considered in order to minimize the potential for errors based on intentional and subliminal prejudice (Risinger, Saks, et al., 90 Cal.L.Rev. 1, 45-50 (2002)).