From a Plane Crash to the Conviction of an Innocent Person: Why Forensic Science Evidence Should be Inadmissible Unless it has been Developed as a Safety-Critical System
Hamline Law Review, Vol. 32, 2009
30 Pages Posted: 1 Aug 2010
Date Written: July 31, 2010
In a criminal trial, it is acceptable to rely on scientific, specifically forensic, evidence. Forensic evidence is often produced through devices omprising both hardware and software, such as a breathalyzer - which measures the level of alcohol in an expired breath - and the equipment used to create a DNA profile. According to existing law, a person may be convicted on the basis of a single piece of evidence. Once a person has been convicted of a serious offense, such as murder or rape, an “ultimate penalty” may be imposed on him, such as life imprisonment or even a death sentence.
Many studies conducted in the past few decades have revealed a significant phenomenon whereby innocent persons are convicted. This phenomenon can no longer be doubted or ignored. Hence, the inaccuracy or unreliability of forensic equipment could lead to the death or prolonged incarceration of an innocent person.
Scientists and legal scholars have pointed out that some areas within the forensic sciences are nearly barren of a scientific foundation, that error rates are in fact higher than usually acknowledged by forensic scientists, and that laboratory regulation and quality control are weak compared to medical, research, other government, and private industry labs. This article adds something new to the scholarship in this area. It draws attention to the development of software and hardware used in crime laboratories, and to other forensic equipment used by the police, and questions why those are not held to the same development standards as other safety-critical devices in other realms where the safety of the public is concerned.
As we shall see below, safety-critical systems, which pose a danger to human life or body integrity and could lead to significant economic loss, are found in many fields and industries, such as medicine, aeronautics, and transportation. In such fields, statutory rules have been enacted that are designed to minimize the danger of mishaps that could lead to catastrophes and significant damage. Regulatory bodies have also been established whose role it is to monitor the procedures used to develop these systems and to guarantee the safety of the end product. These bodies are not satisfied with a test of the final product as a “black box,” because that test is concerned only with the device’s output and not the way it works or its method of development.
Instead, regulatory authorities demand that the device be developed safely at all stages. In particular, the manufacturer is subject to strict requirements related to the software of the device. One of the principles of software validation is that testing the program after it has been coded is not enough to verify software integrity and coherence. It is also necessary to ensure that the design, development and coding of the software, as well as its testing, were conducted in a manner that has prevented the introduction of defects.
As we shall see below, the same caution is not applied to devices used to produce forensic evidence, despite the potential of such evidence to determine the fate of an individual. This is the case in particular with regard to evidence obtained through the use of computer software, which the courts are still willing to admit with an unfounded, dangerous optimism. This lack of caution is reflected in the evaluation of scientific evidence, while the device used to produce it is treated solely as a “black box.” The result is that findings obtained from a device such as a breathalyzer, which would not be approved based on standards applied to medical devices, are considered admissible evidence for the purpose of convicting a person in a court of law.
In Part II of this article we will first explain, in detail, what safety-critical systems are, the importance of the standards applied to their development, and what system safety engineering is. In Part III we will illustrate the current attitude in a court of law towards scientific evidence, acquired using the breathalyzer, which is used to detect drunken driving, as a test case. In Part IV we will try to convince the reader that it is essential to develop forensic equipment as a safety-critical system. Finally, in the epilogue, we call on lawmakers to subject forensic evidence to the standards that apply to safety-critical systems in order to reduce the danger of convicting the innocent.
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