Forensic Science and Law: The U.S. Supreme Court’s Decision in Daubert

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Table of Contents

Introduction
Main text
Summary
Works Cited Page

Introduction

The U.S. Supreme Court’s decision in Daubert (1993) marks the importance of reasoning in cases involving scientific evidence. Prior to this decision, the jury accepted any evidence presented in combination with the Frye test. This test was used as a standard for determining the admissibility of scientific evidence in Federal courts. The precedent is based on the concept of “reasoning or methodology” which means that in outlining the criteria that might be used to determine the scientific validity of the evidence. Thesis In spite of the advantages and opportunities proposed by the Daubert decision, it creates a lot of challenges for forensic science and DNA testing in particular.

Main text

According to the Daubert decision, the Supreme Court took a broad view of “science ” based on the data and reasoning facts considered as expert evidence. The expert evidence is a critical component of many trials, and before the Daubert decision juries were influenced by expert evidence that is not based on a scientific knowledge (Dixon and Gill 2). The Daubert decision assigns the role of federal judges as “gatekeepers” and introduced new standards for evidence testing. The main criteria that judges have to consider involve:

whether a theory or methodology can be (and has been) tested;
whether it has been subjected to peer review and publication;
whether it has been subjected to peer review and publication,
the known or potential rate of error;
the existence and maintenance of standards controlling the technique’s operation;
whether it is generally accepted in the scientific community (Dixon and Gill 3).

In spite evident benefits and opportunities of the new approach, it creates numerous challenges for forensic science and DNA testing. Following Kaestle et al (2006) Daubet “sets a more “lenient” threshold for admissibility than the other; both require a pretrial showing of scientific validity. The principal distinction between the two lies in the question, “who decides the issue of scientific validity” (53).

Taking into account DNA identification technique, it is possible to say that within species, the number of similarities is far greater than the number of differences, but because of the uniqueness of DNA, theoretically, no two people are exactly the same, save for identical twins. In theory, from organism to organism, the sequence in which molecules form the DNA chain differs. Both the White and the Jeffreys methods for using polymorphic strands as an identifying marker—now the Lifecodes DNA-Print and the Cellmark DNA Fingerprint, respectively— individualize by using length polymorphism. This technique is called restriction fragment length polymorphism (RFLP) (Watson and Witkowski 5).

To do this, a relatively large segment of pure DNA must be extracted from each biological specimen (Cheng 1263). The DNA in each person is the same in every cell, and the polymorphic piece of the chain can be obtained from any tissue sample and from many body fluids. The main problem for DNA evidence is that the jury lacks scientific knowledge and skills necessary for careful and deep analysis of the facts presented to the court. Following Kaestle et al (2006)

Under Frye, the trial court defers to the opinions of scientists as to whether a particular scientific advancement is valid. For the reasons given in Part III, this Article submits that forensic DNA does not yet have a strong enough scientific standard for admissibility, and courts should take great care prior to admitting such evidence” (63).

In contrast to many other method, DNA proposes great opportunities to detect a person and present evidence to the jury. For instance, today forensic scientists see genetic fingerprinting as a far more powerful tool than conventional serology, in which blood, semen, saliva, and other body fluids can be tested for the presence of certain blood-group factors, such as the simplest ABO, or Rh-negative/positive typing, or protein markers (Watson and Witkiwski 23). The main challenge is that the court could not objectively consider the scientific validity of the evidence (Cheng 1263).

In a criminal investigation—usually a rape or murder—the specimens usually are blood from the victim, blood from the accused, and the best two or three specimens from the crime scene, such as a bloodstained item of clothing the accused was wearing, or a semen stain or swab in the case of a rape. If the DNA print of the sample matches the print of the accused’s blood, scientists from the DNA-typing laboratories are willing to testify that the chances of the DNA on the sample coming from the accused are very great (Janus and Prentky 1443).

These scientists argue that the chances are usually one in millions or billions that two individuals would present an identical DNA print; the odds vary, depending on the population in question because there are racial and gender differences in polymorphic strands, and various features are more common or less so. The main problem for the jury is that this population statistic theory has been called into question (Cheng 1263; Watson and Witkowski 76).

The other challenge created by the Daubert decision is that DNA evidence is usually admitted against a defendant, and the jury receives a chance to reject its scientific validity. Kaestle et al (2006) explain that “the proffered mtDNA inclusion statistics that will be reported to the jury are scientifically unsound or are not generally accepted in the scientific community. Most courts are simply unaware of the unique aspects of mtDNA typing as compared to nDNA typing, and have not been exposed to the scientific literature discussing the problems with the SWGDAM database” (64).

Allen (1994) and Beyea and Berger (2001) admit that a DNA test determines whether certain polymorphic DNA segments—called alleles—are present in a sample. This produces a much less specific identification of the DNA because large numbers of people may have any one particular allele present in their DNA. By probing for a large number of alleles, however, it is possible to say that a DNA sample came from one particular individual out of 10,000 or 100,000.

Although saying that a particular DNA print may be replicated in 1 in 100,000 individuals within a certain population is by no means saying that the print is unique, when combined with other evidence, it can be a powerful piece of a prosecution’s case ((Watson and Witkowski 32). The technique is especially useful when looking at small DNA samples. Because DNA deteriorates so rapidly, it is not always possible to get a large enough sample to do meaningful testing using the Cellmark or Lifecodes techniques.

These probes bind to different spots when that particular allele is present. So when a forensic serologist—the crime-lab technician who deals with blood samples—testifies that the defendant has a particular blood type and that this blood type is found in a certain percentage of the population, jurors at least can understand the numbers, even though they may not understand the particulars of how those population statistics are derived. Mellon underlines that “Daubert’s stricter standards have caused many Frye jurisdictions to take the trial court’s gatekeeper role more seriously, resulting in greater attention to indicia of reliability traditionally outside Frye’s scope of inquiry” (1097).

The challenge created by the Daubert decision is that DNA technology is unfamiliar, complex, and novel to jurors, however, and the population statistics on which DNA-typing scientists base their findings of probability also are far more complex. The DNA-Print technology used by Lifecodes, the DNA Fingerprint technology used by Cellmark, and the other particular techniques used by the FBI and other forensic labs that do DNA typing are all composites—a number of probes with various statistical probabilities, that then must be multiplied to produce a final statistical probability (Watson and Witkowski 83).

The chance of any one particular probe showing a print at a certain location on the autoradiograph usually is one in thousands and varies among different subpopulations, based on race, ethnicity, and gender (Janus and Prentky 1443).

In addition, a state assembly committee held hearings on whether to legislate regulations of the practice. Defense attorneys argued that while DNA typing is a valid technique in theory, there is no legislated quality control over the commercial laboratories conducting the tests. They noted that the state health department had not yet set quality-assurance standards for DNA typing as a diagnostic tool, which is a technique identical to forensic DNA typing. the experts did not put the blame on Lifecodes, but rather on the adversarial nature of the legal system and its inability to deal effectively with complex science as well as on themselves as leaders in the scientific community for not pushing harder for universal standards in forensic use of the technique (Watson and Witkiwski 82).

In addition to criticizing sloppy laboratory techniques, researchers also have questioned the assumptions about population genetics that led the expert witnesses from the commercial labs to testify that the chance of a person other than the defendant matching the DNA-typing test is one in hundreds of millions or even one in billions (Kaestle and Kittles 53). For instance, Judge Sheindlin’s ruling in the Castro case shows a level of distinction between generally accepted scientific practice and common forensic-science practice not always adhered to in Frye hearings.

Too often, argues Bert Black, an attorney in Baltimore, judges accept the expertise of forensic -lab technicians and their arguments about the ability of their techniques to meet the requirements of general scientific acceptance. Mellon underlines that “The data produced by the developmental validation studies would reveal the kit’s ability to distinguish between true results of the DNA analysis and results that reflect environmental degradation” (1097).

Summary

In sum, the Daubert decision proposes great opportunities for the jury but puts many limitations of forensic identification techniques. DNA allows identifying several genetic markers from a single crime-scene blood sample by separating the proteins using electrophoresis and sequentially staining the sample for different tests. Thus, DNA evidence does not always accepted by the jury and the court. By showing that statistical analysis always is used to determine the probability that the evidence is what an expert asserts it to be, the prosecution could get a judge to allow a new scientific technique to be used and analyzed statistically.

Works Cited Page

Allen, R. J., Expertise and the Daubert Decision. Journal of Criminal Law and Criminology 84 (1994), 1157-1175.

Beyea, J., Berger, D. Scientific Misconceptions among Daubert Gatekeepers: The Need for Reform of Expert Review Procedures. Law and Contemporary Problems 64 (2001), 327.

Cheng, E. K. Independent Judicial Research in the Daubert Age. Duke Law Journal, 56 (2007), 1263.

Dixon, L. Gill, B., Changes in the Standards for Admitting Expert Evidence in Federal Civil Cases since the Daubert Decision. Rand Institute for Social Justice, 2001.

Janus, E. S., Prentky, R. A. Forensic Use of Actuarial Risk Assessment with Sex Offenders: Accuracy, Admissibility and Accountability. American Criminal Law Review 40 (2003), 1443.

Kaestle, F.A., Kittles, R.A., Roth, A.L., Ungvarsky, D.J. Database Limitations on the Evidentiary Value of Forensic Mitochondrial DNA Evidence. American Criminal Law Review 43 (2006), 53-76.

Mellon, J. N. Manufacturing Convictions: Why Defendants Are Entitled to the Data Underlying Forensic DNA Kits. Duke Law Journal 51 (2001), 1097.

Watson, J. D., Witkiwski, J. A. DNA: Forensic and Legal Applications. Wiley-Interscience; 2004.

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Forensic Science and Law: The U.S. Supreme Court’s Decision in Daubert

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