| When Gregor Mendel published his studies of inherited | | | | VNTRs, exponentially increasing the probability that a |
| characteristics of pea plants in 1866, he probably | | | | match between the two specimens is not an error. |
| didn't know he was starting a sequence of events | | | | Statistically an innocent person would be more likely |
| that would end in the 1987 conviction of someone in | | | | to win the lottery than to be inaccurately convicted |
| the United States based on DNA evidence. This | | | | using DNA evidence, assuming that the proper |
| article discusses the history and current status of the | | | | number of sequences is analyzed. |
| use of DNA evidence in the United States. | | | | Where DNA Evidence Stands Now |
| How DNA Evidence is Gathered and Used | | | | The first conviction made using DNA evidence |
| DNA (deoxyribonucleic acid) is a nucleic acid consisting | | | | occurred in Portland, Oregon in 1987. Juries seemed |
| of two chains of nucleotides bonded together in a | | | | hesitant at first to accept DNA evidence as |
| double helix, and is responsible for determining the | | | | conclusive, perhaps because of the complicated |
| inherited characteristics of each person. Historically, | | | | process - which has been extensively simplified for |
| DNA could only be extracted reliably from clean | | | | this article - that lawyers and specialists had to |
| specimens of blood or other body fluids. Due to | | | | explain to the jurors. The process in its infancy left |
| recent scientific developments, DNA evidence can be | | | | much room for defense attorneys to insert doubt |
| extracted and amplified from a variety of samples, | | | | into the cases against their clients. However, as |
| including licked stamps, dental floss, used razors, hair, | | | | science continued to develop, DNA evidence and |
| and even sweaty t-shirts. | | | | technology gained a foothold in the United States' |
| The DNA evidence is taken back to the laboratory | | | | courts. |
| where the sample is cleaned and prepared. The DNA | | | | DNA evidence and associated technologies were |
| is cut into small, manageable pieces using enzymes, | | | | thrust into the limelight when a man by the name of |
| and then it is categorized by size using a process | | | | O.J. Simpson was accused of killing his ex-wife and |
| known as "gel electrophoresis." We all share some | | | | her associate in 1995. DNA evidence also played a |
| 99.9% of our DNA, but there are specific regions in | | | | large role in the case of the disappearance of child |
| our DNA that differ. In certain areas, given | | | | beauty queen JonBenet Ramsey. |
| sequences of the bases adenine, thymine, cytosine, | | | | Just as DNA evidence has been used to convict |
| and guanine repeat themselves. The sequences, | | | | people of crimes, innocent people wrongly accused |
| known as variable number tandem repeats, or | | | | have also been freed based on DNA evidence |
| VNTRs, create a unique personal blueprint that can | | | | analyzed after the fact. Ten people have been freed |
| be used as DNA evidence. | | | | from death row in the United States when DNA |
| The VNTRs are marked with a radioactive compound | | | | technology was finally made available to analyze their |
| that aids in being able to make an x-ray image of the | | | | cases. |
| DNA sequence. These images, which are the DNA | | | | At the time of this writing, several states, prisons, |
| evidence ultimately presented in courts, can then be | | | | and communities are developing programs to create |
| compared to the DNA sample collected from a | | | | DNA databases, especially from those considered |
| suspect. | | | | dangerous felons or high risk criminals. The future of |
| The DNA sample from the crime scene and the | | | | DNA evidence in the United States lies in the hands |
| suspect are compared at a number of different | | | | of legislatures, courts, and responsible DNA labs. |