Forensic science is an important part of many crime investigations. In forensic laboratories, any type of organism is identifiable through DNA analysis. For the criminal justice system, DNA identification aids with apprehending criminals, exonerating wrongly accused people and identifying victims. When mishandled, however, forensic science can lead to questions of quality control and privacy infringement.
Pro: Exonerate Wrongly Accused People
One positive consequence of DNA analysis has been the reopening of old cases. Some people convicted of crimes including murder and rape before the availability of DNA analysis have requested that evidence from their cases be re-evaluated using this technology. When DNA is used for forensic identification, some test results have exonerated convicted criminals, resulting in their release from prison.
DNA analysis may also prevent wrongful convictions in the first place. Before the 1960s, DNA evidence depended largely on ABO blood typing and polymorphic typing. Such tests could narrow the field of possible suspects but could not identify a specific suspect. Today, DNA samples obtained from a crime scene can exonerate wrongly accused people even before prosecution.
Pro: PCR Analysis
Polymerase chain reaction, or PCR, is a forensic process that exactly replicates DNA extracted from a biological sample. This process amplifies one sample with a million copies, which allows DNA analysis from something as small as a skin cell. In turn, even degraded samples of DNA can be analysed, and the minuscule sample required for testing may allow for independent laboratory testing. Multiple test results can then be compared to ensure investigators seek the right crime suspect.
Pro: Identify Victims of Disaster
In addition to identifying suspects, DNA analysis can also be used to identify victims of disaster. For example, the DNA Shoah Project contains a database of people who lost family members during the Holocaust. The database may reunite families separated during that time and also identify victims who are still anonymously buried in Europe. After the attacks on the World Trade Center and the Pentagon on September 11, 2001, victims were identified by DNA in bone and tissue fragments. Such forensic techniques help to solve mysteries, reunite family members and ease the suffering of victims' loved ones.
Con: Inconsistent Laboratory Methodologies
Forensic science has been criticised for lacking standardised practices of analysis. This is largely owing to rapid expansion of DNA practices and different methods employed by private laboratories. Single-locus RFLP, multilocus RFLP and PCR are individual methodologies laboratories use when analysing DNA for law enforcement agencies. Each method uses its own match criteria and reporting methods. Differences of opinion exist within courts as to the reliability and applicability of these methods, and some scientists question their accuracy.
Con: Quality Control Issues
Some have questioned the validity of forensic science because of visible quality control issues. Many defence attorneys have used this in their clients' favour. Such mishandling of forensic evidence leads some law enforcement agencies to dismiss its importance at a crime scene. Mandatory certification programs also do not exist for forensics practitioners or laboratories. Moreover, forensic scientists sometimes ignore performance standards and fail to use accepted terminology in reporting on the results of forensic investigations.
Con: Infringement of Privacy Rights
Investigators often rely on DNA strands found at crime scenes. Those strands are compared to a police database that holds DNA samples obtained from previously convicted criminals. Some scientists fear that a person's DNA profile from the database may wrongly be identified as a match or partial match to a strand extracted from a crime scene. Such an instance can occur even with innocent people who may have been at that scene earlier. Two people may also hold similar DNA profiles, sometimes causing an innocent person to be charged inadvertently.
DNA samples can also provide scientists and investigators with private information such as family relationships and disease susceptibility. Some see access to this information as an infringement on civil liberties. In addition, databases that are believed to be technically secure may be susceptible to compromise. This may lead to tampering with DNA samples or the public release of private information.
- Oak Ridge National Laboratory: DNA Forensics
- National Institute of Justice: "Convicted by Juries, Exonerated by Science"; Edward Connors et al.; June 1996
- National Academies Press: "DNA Technologies in Forensic Science"; 1992
- Sandra Day O'Connor College of Law, Arizona State University: "Solving the Problems that Plague the Forensic Science Community"; Harry T. Edwards, U.S. appellate judge; April 2009