Forensic Science

III. Handling of Scientific Testimony by the Courts

With the increased use of forensic science testimony in the courts, there also must be safeguards against so-called junk science being admitted into trials. The manner in which the courts perform this task is being debated among many experts that offer their services to the court, litigants, plaintiffs, and defendants. In the days before any guidance was issued by the courts, justices used to rely on the “marketplace test” for expert witnesses. Basically, if the expert witness could sell his or her craft and survive in the marketplace, and if he or she offered testimony that was not common knowledge or within the grasp of the average juror, more than likely that testimony was admitted. Note that this did not screen out those who practice mumbo-jumbo science, and it could not distinguish between astrology (a very old tradition that still can make money today) and astronomy. Today, this strategy would not work. Psychic detectives would not be allowed to testify to their experiences in speaking with the dead—something that cannot be verified by any sort of empirical tests, which leaves the court and other experts skeptical. However, a homeopathic doctor who has credentials from a nonaccredited institution may be able to give testimony on the effects of the sage plant on insanity from his self-documented case studies. Thus, the courts must have some sort of method to be able to distinguish between what could be considered science and what can be considered bogus.

The first black-and-white method of screening expert testimony was offered in Frye v. United States (1923). In this case, the defendant was accused of murder, to which he offered an expert to testify to his innocence by analyzing the results of a very primitive lie detection exam (the systolic blood pressure deception test). This witness and subsequent testimony were rejected, since they did not yet receive general acceptance in the field from which they came. This type of lie detection device was new on the scene, and the court made the stand that testimony given and evidence offered should have a real-world basis and be generally accepted among the experts in the field. This will prevent evidence “in the twilight zone” from prematurely influencing court decisions before it can be perfected within the expert’s field.

Frye’s general acceptance test survived until contemporary times, and was hardly mentioned until talk about updating the Federal Rules of Evidence began to stir up controversy. In 1993, this controversy came to a head in Daubert v. Merrell Dow Pharmaceuticals when the Court revised the judge’s role in admitting expert testimony. The decision was to make the judge act as the gatekeeper to screen out junk science and allow the expert testimony that is reliable, valid, testable (falsifiable), and generally accepted. The Court did not mandate that these criteria should be limiting nor inflexible, but it did stress that judges should utilize, to the best of their ability, their analytical skills in making a judgment call on the evidence or testimony’s methodology and standing in the field from which it came. Two more key decisions were made by the Court to enhance the role of trial judges as gatekeepers of expert testimony. In Joiner v. General Electric Co. (1997), the method of appealing lower courts’ decisions on allowing or disallowing expert testimony was set to abuse of discretion instead of a de novo review of the proffered expert testimony. Thismeans that trial judges should be challenged on their decisions to accept or disallow expert testimony only if a plaintiff or defendant can prove that this judge broke a procedural rule in the process of coming to this decision. Complete overviews of this judicial decision were deemed inappropriate. The second was Kumho Tire Co. v. Carmichael (1999), which expanded the Daubert decision to include all expert witnesses, not just those with a scientific background (auto mechanics, accountants that have worked closely with the FBI on fraud cases, and many others without advanced degrees but who have specialized knowledge).

So, the courts are set with the precedent to keep out junk science, but can they actually perform the task well? The Court has spoken about the ability to utilize “special masters” to aid the court in coming to a conclusion on the veracity of offered expert testimony. Some scholars suggest that a research foundation be created, at least for the Supreme Court, similar to what the Congress currently has the capacity to do. This way, the parties can offer expert testimony, but the court can make a counteroffer with nonbiased (as much as this is possible) research that can guide the trial in the right direction. The issue of whether these safeguards, if instituted regularly, assist in keeping out junk science is an empirical question that desperately needs answering.

Today, decisions have been made at the state level to continue to follow a Frye-based system, or a Daubert-based system, or a third system that is a hybrid of the two. The federal system works solely on Daubert principles. As can be anticipated, there are advocates of both Frye- and Daubert-based systems—the differences between them are outside of the scope of this research paper. However, readers should take note that challenges to expert testimony are constantly being litigated. The decisions of these trials will serve to be the most important shaping factors in what will be deemed appropriate in U.S. courts.

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