Teachers' Domain; The Life Science; Forensic DNA Analysis

It was one of the most sensational murders of the century. And it was never solved. Marilyn Sheppard the wife of a handsome surgeon killed by more than 15 blows to her head. Dr. Sam Sheppard. Was convicted of murder in a highly publicized trial. Sentenced to life in prison. He served 10 years until the U.S. Supreme Court overturned his conviction. In a second trial. Sheppard was acquitted but suspicions about his guilt remained. My mother. Was murdered. I want my mother's murder solved. Now the son of Marilyn and Sam Sheppard. Is taking the case to court one final time suing the state of Ohio for two million dollars for the wrongful imprisonment of his father. We're right it was Gilbert needs to convince a jury beyond all reasonable doubt that Sheppard did not kill his wife.

And in this figure. He'd like to use a powerful new scientific tool. Unavailable at the earlier trials that could potentially settle the question once and for all. Forensic DNA analysis human DNA is made up of billions of chemical building blocks at certain locations. The arrangement of these building blocks varies in predictable ways from one individual to another. These variations are called illegals and they are the key to DNA fingerprinting. If enough of them can be observed and compared these genetic variations can identify an individual as uniquely as a fingerprint. Scientists are now able to compare the DNA found at crime scenes to DNA taken from suspects as valuable as it may be in prosecuting crime.

It's DNA's ability to rule out suspects but holds the most power. Gilbert enlist the aid of Dr. Mohamad to hear. A forensic DNA specialist in Indianapolis. He sends to hear a set of artifacts all stained with blood from the crime. Among them. A wood chip lifted from the stairs of the shepherd's house. A section of flooring from the porch to here chooses a test called d q a one. The d q A1 test is designed to work with tiny quantities of DNA. But it isn't very discriminating. The test can identify only eight different illegals in forty two possible combinations. His first step is to increase the quantity of DNA. The test will have to work with.

To do this he places a portion of each crime scene sample into a vial. Then he adds a chemical cocktail that stimulates the process of DNA replication. The samples are then placed into a thermal cycler. Which speeds the process of replication. For precise warming and cooling of the samples. Within hours. Any DNA present in the original samples. Has replicated into millions of copies. He obtains Marilyn's DNA from a few strands of her hair collected after the murder. Finding Dr. Sheppard's DNA proves more difficult. So Sam Reese Sheppard grants permission to have his father's body Exuma. For tissue sampling. Doctor to here can now complete the testing the DNA from each of the

samples is now poured over the sensitized paper test strips and reveal the long awaited results. Each test strip is printed with a set of numbers. The numbers refer to the eight specific the levels the test can detect. Indicators turn blue when the test is detected a specific. In this example. The test has detected the number to a Leo and the four point one. Wants to hear obtains a test strip for each DNA sample. He will carefully chart the results and present his findings to the defense team. At the first trial. The prosecution argued that the blood trail came from a weapon dripping with Marilyn's blood. Carried by the killer as he fled the house. What does the DNA show.

The porch stain tests positive for the four point one. Only the wood chip also shows the 4.1 as well as the illegals 1 point 1 2 and 3. How does this compare to Marilyn Shepherd's DNA. Her Leo's turn out to be one point one and one point three. One or both of Maryland's illegals are absent from the blood trail samples. Marilyn is therefore excluded as a donor to these stains. So the prosecution's theory was wrong. A murder weapon dripping with Marilyn's blood didn't leave the blood trail and whose blood was it. Was it Dr. Sheppard. His aliens turn out to be one point two and one point three.

So Dr. Shepherd. Is also excluded from the blood trail.