The advent of forensic DNA testing has had a radical and widespread impact on legal-judicial systems. The exact nature of this impact varies from nation to nation, depending on the specific needs of the nation, the existing legal-judicial system, and how DNA technology has been applied.

As time passes, both the capabilities of DNA technology as well as the number of nations utilizing this technology continue to increase. At the present time, many nations are taking initial steps in DNA laboratory and testing development, while those nations with more established systems continue to improve their capabilities. In addition to increasing technical capabilities, there is also an improved understanding of how DNA systems and databases can be used more effectively as well as an increased appreciation on how to interpret the trends revealed by the analysis of DNA data. The development of DNA technology in general and DNA databases in particular will have an ever-increasing impact on national legal-judicial systems and societies.

EARLY USE AND ACCEPTANCE OF DNA TECHNOLOGY
When forensic DNA technology was first applied to human sources, the amount of material required for testing was often in the milliliter range. This precluded DNA testing from being able to address the majority of criminal cases. In addition, gaining acceptance of DNA results in the courtroom setting presented its own set of challenges. It would take time for the introduction of a new technology, coupled with the statistical analysis that was relevant to almost every case, to gain admittance in courtrooms. In some early cases, DNA results were not permitted into courtroom testimony. However, as DNA results withstood legal-judicial scrutiny and thousands of peer reviewed studies, DNA technology moved from being a new and rather obscure technology with many unknowns and questions to a common and even required source of information. In fact, several television series in which the focus is on Crime Scene Investigations (CSI) and how DNA can help solve crimes has added Hollywood drama and expanded viewer coverage to such a degree that forensic DNA testing is now considered by many to be the norm in CSI investigations. While the CSI shows are factually flawed in many aspects, their popularity and widespread broadcast have resulted in what is called the “CSI Effect” in which judges, lawyers, and juries may almost demand the use of DNA testing for samples from crime scenes, even if such testing will not add to the weight of evidence. The acceptance of forensic DNA technology has reached such a degree that a recent ruling in New York has stated that it is the right of a criminal defendant to have access to forensic DNA testing. Thus, in less than 20-years, forensic DNA testing has moved from being rarely used (and even circumspect in legal-judicial systems) to being demanded by court systems.

DNA DATABASES
The evolution of DNA databases provides significant opportunity to help solve cold crimes–those cases in which no suspects exist but DNA evidence is available for testing. There are two main methods in which forensic DNA testing can assist in legal-judicial investigations. One of these occurs when suspect and evidence samples are available for DNA testing. The other type of method relies primarily upon the creation of DNA databases for comparison to DNA profiles obtained from crime scenes. Various nations and states within the United States have passed legislation detailing from whom DNA samples can be collected. Early in the creation of DNA databases, most legislative statues allowed only convicted felons to be required to provide samples for testing and entry into national DNA databases. As the capability of DNA databases to aid in solving cold cases was demonstrated, legislation often changed to require that other individuals associated with non-violent crimes be required to submit biological samples for testing and entry into the database. In some states and nations, all arrestees are now required to provide samples for DNA testing.