DNA: A powerful tool in Criminal Justice

DNA: A powerful tool in Criminal Justice.

During the past decade DNA analysis has become a powerful criminal justice tool. DNA can be used to identify criminals with great accuracy when such evidence exists. On the other hand, it has also been used to clear suspects and exonerate persons falsely accused or even convicted of crimes. In one disturbing example of the latter, the State of North Carolina in the USA freed a pair of siblings, one of whom was North Carolina’s longest-serving death-row inmate. Both prisoners had served decades behind bars for the rape and murder of a North Carolina child, until DNA evidence implicated someone else. Source

What Is DNA?

DNA (deoxyribo-nucleic acid) contains individual genetic information about a person, who has the same DNA throughout the entire body located in every cell.

Where Can DNA Be Found at a Crime Scene?

Any residual material left from his/her body at a crime scene will contain that person’s DNA. Examples of bodily materials that contain DNA evidence include these: blood; saliva; hair; semen; mucus; fingernails; perspiration. A DNA sample is usually taken from a suspect by swabbing the inside of that person’s cheek. DNA evidence can be found just about anywhere at a crime scene, even on a victim. Typically DNA evidence may be found on such items as these: clothing; weapons; cups; toothbrushes; tissues; even in the injuries inflicted on the victim.

Nonetheless, although DNA evidence can be very accurate, there is sometimes the danger of that evidence being compromised (see below).

How Is DNA Collected at a Crime Scene?

DNA evidence can be easily contaminated during both its collection and its storage. This can occur when DNA evidence mixes with other persons’ DNA. Tellingly, this year the High Court unanimously allowed an appeal against the decision of the Full Court of the Supreme Court of South Australia and acquitted the appellant of murder. See, Fitzgerald v The Queen [2014] HCA 28 (13 August 2014). Fitzgerald had been convicted of murder and causing serious injury as part of a group of six people involved in a home invasion that had taken place on the 19th June 2011. Fitzgerald claimed he was innocent, arguing that the DNA evidence found on a didgeridoo linking him to the offence had been transferred to his co-accused during a handshake earlier that evening. Hearing the appeal, the High Court held that the evidence was not sufficient to establish the prosecution case beyond reasonable doubt and that alternative hypotheses consistent with the appellant’s innocence had not been eliminated by the prosecution. The contentious issue was whether or not the appellant’s DNA, derived from his blood and found on a didgeridoo, was present because he had been at the scene of the crime with his co-accused, or whether the DNA had been present on account of a “secondary transfer” occasioned by an earlier handshake. Allowing the appeal, the High Court concluded that the prosecution had not established beyond reasonable doubt that the accused had been present at or participated in the attack.

A particularly striking example of the fact that DNA evidence should not be relied upon without careful scrutiny of the circumstances surrounding each case occurred in Germany in 2009, when police admitted that a woman they had been hunting (dubbed “the phantom of Heilbronn”) for more than 15 years never existed. The “phantom of Heilbronn” had been connected to six murders and an unsolved death based on traces on DNA found at the scene. Police later found that swabs used to collect DNA samples had been contaminated by an innocent woman working in a factory in Bavaria. The company that had made swabs used at the crime scenes said that the swabs had been designed for medical not analytical use, and that there had been no requirement for the swabs to be free of DNA. Source. New South Wales police, by contrast, have been collecting DNA samples from thousands of criminals with spent convictions hoping to solve both cold cases and even future crimes. This entails building a comprehensive database beyond the 1,000 samples already collected; a further collection of 2,000 samples over the next 12 months have been proposed. Source. Should you wish advice on this matter, please contact AZ Legal.