Over the past two decades, DNA profiling technology has revolutionized many aspects of criminal investigation (while providing material for numerous popular TV shows like C.S.I.). In fact, DNA profiling has largely replaced fingerprinting as the primary and most reliable method of uniquely identifying an individual and placing them at a crime scene. And DNA profiling technology has allowed many other legal questions to be settled unambiguously, such as biological paternity, immigrant status, and more. DNA profiles are now standard pieces of evidence in a variety of courtroom settings.
DNA profiling is a technique developed and perfected over the last 25 years to uniquely identify individuals based on their DNA – the genetic material that is present in each of the billions of cells in our bodies. DNA is essentially a sequence of “letters” that encodes the unique human information within us, with slight variations. These important differences in the DNA between individuals make us unique and are used by scientists in DNA profiling.
In a typical forensic investigation involving DNA profiling, a crime scene or crime victim is sampled for possible traces of bodily fluids or other sources of DNA that could identify individuals at the crime scene.
In cases of rape, examination of the victim by qualified medical staff will typically include sampling of vaginal contents, skin, clothing, and the area where the crime took place, as the perpetrator may have left semen or other sources of his DNA on the victim or nearby.
Advancing Beyond Fingerprint Technology
Prior to the advent of DNA profiling technology, many cases relied on fingerprints (when available), or the more subjective circumstantial evidence or person testimony. Fingerprints are highly unique, but they are not always left at a crime scene and can be prevented by a savvy criminal.
DNA evidence can be harder to hide, as it can come from semen, a stray hair follicle, the shedding of dry skin, or other bodily sources. Thus, DNA technology has many significant advantages for criminal investigation over fingerprints.
Samples taken from a crime scene are documented and carefully guarded to ensure their integrity throughout the collection and testing process.
Remember the 1995 O.J. Simpson trial? You’ll recall the defense introduced doubt about the integrity of DNA samples taken from the crime scene. Today, extensive safeguards are in place to prevent these issues when this evidence is presented in the court. A standard component includes providing documentation of the chain of custody of these samples.
Scientists can use DNA testing to examine specific sites in DNA identified as being different between individuals. Only in cases of identical twins do two individuals have the same DNA sequence pattern at all the sites commonly tested. In cases where there may be some ambiguity in results, further tests can be run to resolve and eliminate the ambiguity.
One of the most important benefits of DNA technology in the courtroom is the ability to exonerate individuals that may be wrongly accused or even convicted and imprisoned based on less objective, circumstantial evidence. The Innocence Project specializes in identifying and freeing those in prison who may have been wrongly convicted by taking advantage of the power of DNA testing.
Additional uses of DNA technology in the courtroom include the establishment of paternity, in custody and child support cases, and establishment of family relationships, in immigration cases. In these cases, DNA profiles can provide unambiguous evidence of blood relationships, including parent-child, sibling, cousin, and grandparent-grandchild. More distant relationships do become harder to establish, but DNA profiling can act as a critical adjunct in establishing these relationships as well.
DNA testing for courtroom cases can be handled through a fully accredited testing laboratory like DNA Diagnostics Center. The center coordinates collections of DNA samples for attorneys or clients, and follows a strict chain of custody in every legal DNA testing case, to ensure legal security of the results.