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