The Misuse of Dna Evidence In Homicide Cases

The Misuse of Dna Evidence In Homicide Cases

Introduction

As a new technology in criminal justice, DNA is reforming the criminal justice system, in that it can help solve crimes with unprecedented accuracy. DNA evidence is based on small samples of genetic material from individuals that are collected at the scene of a crime, tested, and stored, and later used as evidence in court. The tremendous value of DNA evidence resides in the confluence of two factors: that violent crime typically results in the shedding of biological material in the form of blood, semen, saliva, small amounts of skin, or hair; and that DNA found in the cells of these samples holds the unique genetic code of the individual to whom it belongs. Once the DNA is analyzed in a crime laboratory, it can be compared to the DNA of any individual, whether a suspect, victim, or witness. If a genetic concordance (the presence of the same trait) is found during this comparison, a strong inference is formed that the person is the donor of the biological material. The term match is discouraged, as it is misleading. This evidence aids investigators immeasurably in determining what happened during a violent act, and who was involved in it (Lander & Budowle, 1994).

DNA evidence is the most reliable and accurate type of evidence that exists today, far more reliable than other types of evidence such as eyewitness identification and confessions. DNA evidence has helped solve crimes as well as exonerate individuals who have been wrongfully convicted. This last use of DNA is helping to reform the criminal justice system by revealing wrongful convictions due to the unreliability of eyewitness identification, coerced confessions, and other, less discriminating forms of physical evidence. However, using DNA evidence also raises some legal and ethical problems that must be addressed in order to uphold the constitutional rights of both defendants and citizens (Jeffreys et al., 1985).

DNA typing in criminal justice emerged from a history of the use of genetic markers as early as 1900; more recently, the admissibility of DNA evidence has created legal and ethic issues, the problem of post-conviction DNA testing, and arguments for and against DNA database expansion as well as the future of DNA research.

The Misunderstood Science of DNA Testing

One facet of DNA typing that is frequently overlooked, dismissed, or misunderstood is the population genetics (typically referred to as statistics) aspect of the discipline, in large part because the numerical aspect is intimidating to many people. However, the power and appeal of DNA resides predominately in this area of the field; if every person among millions in the worldwide population had the same DNA, there would be no point in doing the testing, because the likely donor of a sample could not be determined. It is precisely because some statistical significance (or weight) can be applied to the finding of similar types between a crime stain and a specific person that DNA has become such a valuable tool in ...