DNA exonerations and criminal justice outcomes

DNA

The emergence of DNA testing has resulted in the exoneration of many people convicted of crimes. The ACLU (2011) has stated that 17 people on death row were exonerated as of September, 2011. A project in Virginia found 33 individuals convicted of sexual assaults who between 1973-1987 who were still incarcerated in 2012 and whose innocence was demonstrated by DNA testing (Michaels, 2012). DNA testing has proven effective at uncovering since instances of justice gone unserved, because of the unique nature of DNA testing.

Each person's DNA is unique, as a genetic fingerprint. This is the main value that DNA testing has in forensics. Often, before DNA testing was introduced, convictions could be made on the basis of anything from fabricated evidence to weak witnesses. There has always been a certain percentage of instances where innocent people were convicted, even in capital cases. DNA testing, however, has been used in recent years to right these injustices.

The ACLU (2011) notes that modern scientists can readily distinguish DNA, such that identifying a match between two DNA samples is possible. This is the case except in the instance of identical twins and bone marrow transplant recipients. DNA is found in every single cell of a person, so the sample taken from the victim or the crime scene can be enough to overturn a conviction, depending on the details of the sample and the details of the case. A sample from the convict is taken -- from the skin or hair perhaps, and this is matched up with a sample from the crime scene. Even in cold cases, for example, there might be evidence from fingernails, hair, blood, semen or other part of the perpetrator's body. The scientist then tests the DN A from the two sources for a match. There is a very high degree of certainty in this test. Where a match does not exist, it may be able to prove innocence. There are times when a failed DNA match does not prove innocence and therefore does not constitute full exoneration, but this depends on the details of the case. The DNA evidence collected from the crime scene needs to still be in good condition, which is not always the case.

In many instances, either the testing was requested by the convict or it was solicited by the state in conjunction with a broader program (Lithwick, 2012). In Virginia, a program has been run for years, and while there are criticisms about the cost, it has led to exonerations, even during the phase of random testing. Today, there is a move to allow for DNA testing if not during the investigation then certainly at the point of conviction (Mears, 2013). There are other options for the timing of tests, and there is no consistent policy for this in any jurisdiction. At present, DNA testing is often done on an ad hoc basis.

It is worth noting that the tests are still a work in progress. While post-conviction DNA testing is allowed for 49 states, there is still work being done on the testing procedures. It is now possible to perform DNA testing with a very small sample, something that was not possible when the technique rose to prominence in the forensic business. The legality of the testing being a state issue, the environment for it is quite complex. Prisoners need to understand their state laws -- some prisoners would at this point have no access to DNA testing that could exonerate them. However, by identifying that the person who has been convicted was not the person who was at the crime, it is possible to exonerate people who have been wrongly convicted, and therefore to have the conviction overturned.

2. It is not possible to determine how successful this is compared with the number of cases. The important number of cases here is the number of people who have been wrongly convicted -- that is the denominator when considering the success rate. How many wrongful convictions are discovered is a function of how many there were in the first place, not a function of the testing. If there were no wrongful convictions, the testing would find nothing even if the test was 100% effective. So the reality is there is "success rate" that can be determined because the denominator is unknown.

What is known is that dozens of people have been exonerated through the use of post-conviction DNA testing. There are more such cases that the general public perhaps realizes, and the fact that there were 17 cases on death row should be enough to give anybody pause for thought.