Everyone at some point in their lives dreamed of being a detective. There was something thrilling and exciting about using clues to solve mysteries, and bringing those responsible to justice. As technology exploded onto society, the mysteries and crimes became more advanced. Luckily, so did the methods of collecting clues. For those who are achieving their life goal of being a detective, collecting evidence at a crime scene has never been easier! Detectives today can take the smallest piece of organic material (such as hair or blood), and find the person it belongs to. How is this possible? DNA.
When detectives find organic evidence at the scene of a crime, they send it in for DNA testing. This process requires taking the sample, and separating it into sections of different lengths through enzymes. Next, the lengths are organized through a process known as gel electrophoresis. The end result is a series of bars that show a sequence of DNA. Using this sequence, scientists and detectives can compare it to the DNA of their suspects, to see if they match. Criminals never expect that they would be leaving a DNA fingerprint at a crime scene! Many are caught by this unrefutable evidence. Many of the wrongfully accused are exonerated, as the evidence proves their innocence.
This blog post begins with Dr. Sam Sheppard, a man accused of murdering his wife. He was sentenced to jail for life over his crime. Years later, Dr. Sheppard’s son, also named Sam, has come back to argue his father’s innocence. The questions you see are designed to bring forth the key aspects of this historic trial. (See for yourself! Article can be found at: http://www.pbs.org/wgbh/nova/sheppard/). This time, DNA testing will be used to find out the truth behind the Sheppard murder trial!
1.) In your opinion, what role (if any) did newspaper stories and editorials have in the outcome of the original trial of Dr. Sam Sheppard?
The press had a major role in this trial. Throughout this entire ordeal, the press was there to get the scoop. Sadly, they seem to have caused more complications than they were worth. For one, many of the headlines of news reports were very biased. They would read “Doctor Balks at Lie Test”, or “Why Isn’t Sheppard in Jail?”. Most of the time, these articles were chalk full of false, or misinterpreted information. This would influence not only the officials (for example, Dr. Sheppard was arrested shortly after the second headline I mentioned was released), but also the public. Countless editorials, rumors, cartoons, inuendos, and articles were written about the case. As if this wasn’t bad enough, all of his court trials were fully publicised. His son, Sam, was unable to attend his mother’s funeral, as the press was so overwhelming.
As a whole, the press effected the situation in a negative fashion. They were causing Dr. Sheppard to lose his sense of privacy, as well as turning him into a public “bad guy”. As a whole, this really impacted him and his remaining family. Inversely, when his trial was revisited, public releases such as the movie ‘The Fugitive” and Paul Holmes’ book “The Sheppard Murder Case” started to support him, rather than cause him trouble.
2.) What is the function of the restriction enzymes in DNA fingerprinting?
The function of the restrictive enzymes used in DNA fingerprinting is to cut the sample of DNA into segments of different lengths. For example, say there is the pattern “GATTCTA” within a segment of genetic material. There is a certain enzyme that, whenever it finds that pattern, will attach and seperate the material at that point. There are many different types of enzymes that break the sample at different points. As the patterns occur differently in each person, the end result (their DNA sequence) will be unique.
3.) What is the function of the agarose gel electrophoresis step?
The function of the agarose gel electrophoresis step is to separate and organize the segments of genetic material according to lengths. An electric current runs through the gel. Genetic material has a slightly negative charge. As a result, the material will be attracted through the gel to the positive side of the current. The gel acts as a filter of sorts, allowing smaller molecules (shorter strands) to travel farther. The end result will be the strands being lined up, according to size.
4.) Why is a nylon membrane used to blot the DNA?
A nylon membrane is used to blot the DNA because it is a successful absorbent material. The gel with the DNA segments is too thin and too fragile to handle. So the membrane, being more durable, is placed over the gel. DNA is then sucked up onto, and impresses upon, the membrane. Then, radioactively labeled probes are added to the membrane, as they attach to certain sequences. This will help in identifying the components of the sample.
5.) What does a dark spot on the X-ray film indicate?
A dark spot represents where the probes have attached themselves on the DNA fragments, which is on the nylon membrane. This represents the DNA “fingerprint”. The information gathered from the X-ray film is then compared to the DNA gathered from various suspects, to help solve the mystery/crime.
Thanks to the case of Dr. Sam Sheppard, we now have a better understanding of how the whole DNA fingerprinting process works. Now we know how a sample of organic material can be used to solve a crime. This blog post is now going to switch gears, and focus on another case. The new case is about a man named Ronald Cotton, who was wrongfully accused of rape. Among the people listed in this discussion are DNA expert Peter Neufeld and Cotton’s lawyer Barry Scheck. We will apply what we learned from Sheppard’s case to Cotton’s case, and see how DNA testing can be used to exonerate (free) an innocent man!
6.) What evidence was initially used to convict Cotton?
The evidence that convicted Cotton was not very definitive (sadly, it was enough to send him to prison). This evidence includes a victim making identifications in both photos and a police line up, a flashlight used in the case was similar to one Cotton owned in his house, and the rubber consistancy of Cotton’s shoe matched that found at the scene. Needless to say, this evidence is not very worthy or substantial.
7.) What did the DNA evidence show?
When DNA testing was applied, the evidence, found on both underwear and private region of a victim (from semen), concluded that Cotton was innocent. The DNA of Cotton did not match the specimen found at the scene. Ironically, it matched a man from prison who openly admitted to the crime (the jury was not able to hear his confession, however, to validate his claim).
8.) How could DNA fingerprinting be used to prevent a false conviction if a case like this was being tried today?
DNA fingerprinting can be used to provide a definitive and conclusive answer as to who is responsible for the crime committed. By going straight to DNA testing, many false convictions can be prevented. Had this occured with the Cotton case, Cotton would have been able to avoid 10 and a half years of prison time (he was sentenced to life, but only served the given amount before being proven innocent). By properly using these tests, conviction rates can be more accurate!
9.) What percentage of convicts are unjustly convicted of sexual assault cases, according to Neufeld and Scheck?
DNA expert Neufeld, and Cotton lawyer Scheck, both agree upon the number of unjustly convicted convicts in sexual assault cases. They say 25% of the convicts are being exonerated, having been proven innocent. This number is extremely high! Plus, it shows just how frequently the wrong people are punished, while the guilty are free (which is disturbing to think about, in my opinion).
10.) The O.J. Simpson trial was one of the most visible trials that attempted to use DNA evidence. In the end, the DNA evidence was not satisfying to the jury, who acquitted Simpson. What do Neufeld and Scheck believe about the impact of the O.J. Simpson trial on the use of DNA evidence?
When looking back at the O.J. Simpson trial, a case that made DNA testing famous, Neufeld and Scheck have very similar things to say. They say that this case shows the tremendous potential within the technology we have today. This technology is very important, as it holds the power to decide the fate of some people. Also, Neufeld made a point ins aying that this “is not a law of science, but more of an applied science”. This means people have to be involved to apply the technology to the case. In turn, since people are involved, mistakes can happen. It is very important to be cautious, and apply this science wisely. Scheck said that many innocent people, using only a fraction of the resources O.J. Simpson used in his case, could be exonerated. This represents the responsibility involved in using this effective method during investigations.
As you can see, DNA testing is a very crucial component in criminal investigations. We have looked into Dr. Sam Sheppard, and discovered through his case how DNA testing works. Then we applied this knowledge to Ronald Cotton’s case, and saw how this process can be used to save an innocent man. Clearly, the outcomes of many cases will be drastically changed by this advanced region of science. All that is needed is for a detective to find a single, DNA fingerprint!