Poetry of the Soul

Come See What's Within

History and practice of DNA

This was a speech I presented at a state competition and won with. It covers the history, techniques, parts, criticisms, and famous cases dealing with DNA.

You are the lucky buyer of a Super Bowl 34 game ball. The only problem is, how can you tell if it’s a legitimate game ball or just another fake? Luckily for you, the NFL was a step ahead. All the game balls from Super Bowl 34 were marked with a special synthetic, genetic strand that would only appear under a special laser. That way only legitimate game balls would be sold. And what made this possible? Welcome to the world of forensic science and DNA testing. Forensic science, at its basics, is the application of a broad spectrum of sciences to answer questions of interest to the legal system. And DNA, which stands for Deoxyribonucleic acid, is a nucleic acid that contains the genetic instructions for all living beings. In fact, there are only 3 million bases, or a tenth of a percent, that vary in the DNA from one person to another. For now, lets look at DNA and the processes used in DNA testing.

Any type of organism can be identified by the examination of DNA sequences unique to that species. To identify individuals, forensic scientists scan 13 DNA regions that vary from person to person. That data is then used to create a DNA profile for that person. This DNA can be found in bone, blood, hair, nails, and other body tissues in or on a body.

The basis of DNA testing is this: Scientists design probes that bind to the DNA in a sample. A series of these probes attach to a sample, and it creates a distinctive pattern for the subject. The subject sample and the evidence sample are compared to see if there are any markers that are the same. Now, one marker isn’t usually unique to any one subject. However, if two DNA samples are alike in four or five regions, odds are that you’ve found a match. To obtain and read these markers, forensic scientist use three basic techniques: RFLP, PCR, and mtDNA.

Restriction Fragment Length Polymorphism, or RFLP, is a technique for analyzing the variable lengths of DNA fragments. An enzyme cuts the DNA. Then, through a process called gel electrophoresis, individual strands of DNA are separated for examination. RFLP was one of the first applications of DNA analysis. Because it requires large amounts of DNA, it is no longer used in the same capacity as it once was.

PCR, or Polymerase Chain Reaction, uses a DNA polymerase to amplify a piece of DNA and to make millions of exact copies of that strand of DNA. From there, gel electrophoresis separates out the strands. The benefit of PCR is that tiny samples, down to the size of a few skin cells, can be used.

Finally, we have mtDNA, or mitochondrial DNA analysis. Forensic laboratories occasionally use mtDNA comparison to identify human remains, and especially to identify older unidentified skeletal remains. MtDNA uses DNA pulled from the mitochondria of the cell, instead of the nucleus which is used in the other two test. Although mtDNA is not specific to one individual, it can be used in combination with other evidence to establish identification.

Forensic science itself goes back to the ancient Greeks. The Greeks studied the very basics of a murder to decide if someone’s death was a homicide or suicide. This was of interest because the Greeks viewed suicide as a dishonor to the Gods and if ruled suicide, the body would not be given proper burial. Despite the long background forensic science supports, it took until 1985 for the father of DNA testing, Dr. Alec Jeffery, to discover that certain regions on DNA contained sequences that were repeated over and over again. He also noticed that DNA varied from person to person. From this discovery to present day, DNA testing has seen tremendous growth in the development of its ideas and techniques. It has also drawn the interest of many high profile court cases and the news media. Today, there are over 150 public forensic labs. Here in Georgia, the GBI has 8 locations throughout the state providing forensic services to local criminal justice agencies.

Lets go to the crime scene. There are many objects on a crime scene that can contain DNA evidence. Weapons can contain sweat, skin, blood, and tissue. Dirty laundry can contain blood and sweat. And even something as simple as a fingernail fragment can contain blood, sweat, and tissue. Because evidence can be widespread, crime scene integrity, or protecting the scene, is crucial. As a basic rule, all law enforcement personal should refrain from eating, drinking, or smoking on the scene, as well as touching anything without proper protection. Knowing the chain of custody, or who touched the evidence, is equally as important as to avoid any outside contamination. Compromised evidence, no matter how solid, will not appear as reliable in court.

In the same light, proper measures must be taken when transporting and storing the evidence. For example, you wouldn’t want to place DNA evidence in the trunk of a car, because it can degrade the sample. If it is stored dry and frozen, a DNA sample can be successfully used in a DNA test up to 20 years after its original collection.

At this point, there should be some clear advantages of DNA testing: Identifying an unknown killer or rapist. Finding out the identity of a child’s father. Even tracing ancestral lines back dozens and dozens of generations.

However, there are some major criticisms that might be less obvious. The primary concern is over privacy. DNA can provide many aspects into ones personal life, such as disease, legitimacy of birth, and perhaps predispositions to certain behaviors and sexual orientation. Cost is another concern. Due to the lack of better technology, one DNA test can cost the state upwards of $10,000. Finally, many states don’t order the destruction of DNA after its used, so a persons entire genome can be available for many years after their trial, no matter found guilty or innocent.

There is also a major disagreement all throughout the United States as to who should be forced to submit a DNA sample. As of September 2007, all 50 states have laws that require convicted sex offenders to submit DNA. 44 states have laws that require convicted felons to submit DNA. 9 states require DNA from persons convicted of certain misdemeanors. And 11 states have laws authorizing arrestee DNA sampling. These samples are then stored in CODIS, a database that the FBI uses in the event of unidentified DNA appearing in a new case. The question is raised when a persons 4th amendment right of legal search and seizure is broken. This is an issue that the Supreme Court hasn’t made a ruling on, so the debate shall continue until such a time that a national standard is passed.

Concrete DNA results usually turn up a positive outcome in the legal system. However, this isn’t always the case. The most famous example, perhaps, is the trial of former football star O.J. Simpson. Despite the fact that Simpson was acquitted, there was substantial evidence that showed his guilt. There was hair and fiber evidence that linked him to a hat found on the scene. DNA analysis also showed that blood found on a glove in Simpson’s home and car belonged to that of the two victims. The district attorney went as far as to say that, “the search of his own Ford Bronco and into his home on Rockingham is devastating proof of his guilt.” However, all the physical DNA evidence that proved his guilt wasn’t enough in the minds of the jurors to convict him, and Simpson was later found to be not guilty. There are many theories as to how Simpson was found innocent, but the most likely in my mind seems to be that since DNA testing is such a new field of study, it doesn’t hold full credibility in the minds of jurors.

The opposite side of DNA would be the innocent lives it has saved. According to a study done in 2005 by National Geographic, 14 death row inmates have been freed with the help of DNA evidence. Since DNA technologies are changing everyday, fragments that at one time either couldn’t be tested, or could have been misread, are opened back up for testing as the technology advances.

DNA analysis and forensic science as a whole is a fascinating and vast area of study that continues to grow. Today, you were introduced to the basics, shown ideas and methods used to gather and analyze DNA, the history, advantages, disadvantages, and how DNA evidence is used today in legal cases. I hope you have gained a greater understanding of DNA and will have greater insight the next time you hear a news report about the “new forensic evidence found in the investigation” or even the next time you buy the winning game ball from the super bowl. Thanks for your time.