In Shakespeare's MacBeth, the queen wanders through her Scottish castle lamenting the blood on her hands and crying, "Out, damned spot, out!" Shakespeare was onto something. Blood stains are really hard to get out. And today, with the advent of DNA matching, it's even harder for criminals to mask their violent deeds, as just trace amounts of blood and other biological materials can put investigators hot on their trail.
DNA is the fingerprint of our biology, and in the last few years, DNA matching has grown from a judicial novelty into the cornerstone of many a prosecutor's case. High-tech DNA analysis has even become commercially available, with companies like Houston-based Identigene promising to reveal the paternity of disputed children.
On the law enforcement front, DNA testing has helped convict the guilty, exonerate the innocent, and confuse the hell out of at least one jury pool (State v. Simpson). With DNA databanks already in operation in more than 30 states and authorized in every remaining state, you can see why a growing number of cold cases are finally getting cleared through DNA matching.
But what do you as a street cop need to know about DNA?
Deoxyribonucleic acid (DNA) is the genetic material found within the cell nuclei of all living things. In fact, a complete sample of our DNA can be found in a variety of our body's cells, including muscle cells, brain cells, blood cells, sperm cells, and others.
The DNA of one cell is identical to that of every other cell within the same individual. But there's one notable exception: the red blood cell. Because red blood cells lack DNA, all DNA from blood samples comes from white blood cells.
By judicial standards, DNA testing is a relatively new tool. Originally used to detect the presence of genetic diseases, DNA matching made its forensic debut in the United Kingdom in 1987, when it helped convict Robert Melias of two rape murders. The years since have seen DNA testing playing instrumental roles in both civil trials and criminal prosecutions.
Police departments’ crime labs have had to keep up with increased use of DNA technology in law enforcement by hiring more personnel. But a lack of funding to store and test these samples hinders the process. Departments across the country have a backlog of untested rape kits and other DNA samples in evidence warehouses.
Despite its recent addition to the judicial system, DNA testing is increasingly becoming the benchmark by which culpability or innocence is decided, and fingerprinting is fast losing its favor. Still, DNA matching does have its detractors.
Some critics contend that DNA profiles may not be "unique." Others believe that DNA testing is being used in court to convict people before any real judicial scrutiny of the technology has been completed. They also argue that the quality of testing from laboratory to laboratory may produce inconsistent results.
The collection and retention of DNA samples are also concerns. Evidence samples are often obtained under less than ideal circumstances, and that may lead to the DNA deteriorating or becoming contaminated. This possibility was milked by the Dream Team in the Simpson murder case.
Randy Nagy of the independent forensic DNA lab Bode Technology Group believes that there are two pressing concerns facing the future of DNA in law enforcement. First, there's the issue of training. Officers need to know what DNA testing is capable of accomplishing and how to maximize its benefits. Second, law enforcement agencies need the funds to test the samples.
Time and Money
According to the experts, shortfalls of funding have resulted in untested samples piling up in evidence warehouses. "Currently, there are believed to be some 180,000 rape kits gathering dust in police department basements," Nagy explains. "And some estimates are as high as 300,000."
Testing that backlog of samples won't be easy. However, Dean Gialamas, assistant director of the Los Angeles County Sheriff's Department Crime Lab, says that recent advances in the technology have had commensurate impact in forensic science's ability to obtain and test DNA evidence. While the general turnaround time is a week or two, the LASD lab has been able to complete some DNA testing within 52 hours.
Advances in technology and testing methods mean that not only do investigators have greater chances of clearing cold cases than ever before, but they may also clear many crimes not conventionally considered to be obvious DNA test candidates. For example, just five to 10 minutes of post-carjacking driving can be enough for a suspect to leave viable DNA evidence on the steering wheel.
A growing ability to obtain viable trace evidence means that the damning evidence serial rapists and other sexual predators have left through brief tactile contacts such as fondling, kissing, or licking can now be tested. Nose and ear pieces from eyewear left at crime scenes have been valuable sources of DNA evidence, as well.
As the technology has become more refined and its uses expanded, there has been an explosion of forensic labs and personnel to deal with DNA testing. In fact, the volume of case loads is the biggest factor in determining turnaround time.
And for some cases, the load defies description.
DNA testing of the World Trade Center victims could take years to complete. Even then, the remains of more than 800 victims of the 9/11 attack may never be identified.
Medical examiner Dr. Robert Shaler says that almost half of the body parts and fragments sent for DNA testing came back incomplete because they were subjected to prolonged water and fire damage in the rubble where the towers once stood. Still, DNA matching of some of the more than 20,000 body parts recovered at Ground Zero has yielded the identification of more than 1,229.