The Rape That Wasn't
by Sarah Robinson
1. I looked up "First case DNA technology was used to exonerate someone". This search took me to: http://www.law.northwestern.edu/legalclinic/wrongfulconvictions/exonerations/il/gary-dotson.html.
On July 9, 1977 the police found Cathleen Crowell in a suburb of Chicago, clothes stained and in disarray. She told police she was walking across a parking lot when a car with three men darted toward her and two of the men jumped out and threw her in the back. One of the men joined her in the back, tore her clothes off, raped her, and scratched letters into her stomach with a broken beer bottle. The police took her the hospital where the doctor performed a rape examination that found semen and pubic hairs. When at the police station Cathleen worked with a sketch artist and described a young, white man with shoulder-length hair and no facial hair. Cathleen later said the police pressured her into picking a mug shot for a book but the police denied the allegation. She picked a photo of a man named Gary Dotson. Cathleen had lied because she had sex with her boyfriend the day before and thought she might of gotten pregnant. She wanted a cover story for the pregnancy.
During the trail there was many problems and obstacles Dotson would have overcome. One of the witnesses, Timothy Dixon, said he had done "graduate work" at the University of California at Berkeley but instead it was just a two day extension course. Dixon did much of the forensic work on the case.
The prosecution told the jury the pubic hairs matched microscopically to Dotson when they were in the pre-DNA era. They could not have known those hairs matched Dotson.
Dotson was released from prison on April 4, 1985 with a $100,000 bond pending the hearing that was a week later. At the hearing Judge Samuels revoked the bond and sent Dotson back to prison. The Illinois Supreme Court reinstated the bond on April 30, 1985. Dotson was not free, he was on parole and any violations of the norms of society would be punished by formal charges or a trial. Gary Dotson was sent back to prison on September 4, 1987.
On October 26, 1987 Thomas M. Breen read a news story about DNA technology. Alec Jeffreys was using RFLP or Restriction Fragment Length Polymorphism to link criminal suspects to crimes. Jeffreys performed the test but fail because the DNA had decayed to much. The governor then found a new test that could be performed, known as PCR or Polymerase Chain Reaction. This type of test could only include or exclude a suspect among a group of people who could have been the source of the DNA. On August 15, 1988, Edward Blake, told the governor, prosecutors, and Thomas Breen that the test positively excluded Gary Dotson and included the boyfriend as the source of DNA in the underwear.
2. Next I looked up "How PCR works" and my search took me to https://www.genome.gov/10000207.
To use PCR you have to amplify small segments of DNA. Today PCR is used for DNA fingerprinting, detection of bacteria or viruses, like AIDS, and diagnosing genetic disorders.
3. I did not get the information I needed from that wed site so I went back to the search page and picked: http://www.nature.com/scitable/topicpage/scientists-can-make-copies-of-a-gene-6525968.
There are three steps to PCR: Denaturation, Annealing, and Extension.
The DNA is heated between 90 and 100 degrees Celsius. This breaks the bonds joining the two strands of DNA.
The DNA is quickly cooled between 30 and 65 degrees Celsius. This gives the primers the opportunity to bind or anneal to complementary sequences on the single strands of DNA.
The DNA is heated back up to 60 to 75 degrees Celsius. A DNA polymerase begins making a new strand by attaching primers and then adding dNTPS to the template.
The number of copies doubles with each three step cycle.
4. I did not know what dNTPS are so I looked up "What are dNTPS" and this search took me to: http://www.ncbi.nlm.nih.gov/genome/probe/doc/TechPCR.shtml.
dNTPS are single units of bases, Adenine, Cytosine, Guanine, and Thymine. Theses are the building blocks of DNA.