Carleton College News Bureau

 

Contact: Sarah Maxwell
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May 30, 2000
Sp99

Carleton College Student Assists Bureau of Criminal Apprehension
Burns Develops Protocols for Identifying Bodies by DNA Extracted from Teeth

Northfield, Minn.-Carleton College senior Megan Burns has spent the last two terms of her undergraduate career as a student worker at the Minnesota Bureau of Criminal Apprehension (BCA), doing research that ultimately could identify victims in kidnapping, arson, and unsolved murder cases. With a team of researchers, Burns has been researching ways to use DNA samples taken from human teeth for positive identification of victims in criminal cases. The protocols that they have developed are now in use by the BCA.

"The research I am doing is important for the advancement of forensic science," said Burns, a Seattle native. "The research that the scientists and I do here not only helps solve crimes, but also it helps clear innocent people of accusations which could ruin their lives."

DNA typing of blood or body fluid has become a commonly used tool for identifying human remains in homicide and death investigations. However, in cases where a body is badly burned or decomposed or altered in an attempt to cover a criminal act, blood can be deteriorated or contaminated and DNA typing can produce inconclusive results. Tooth enamel serves as a protective casing for the dental pulp, from which DNA can be extracted, leaving the pulp as a more viable source for DNA. Burns' research centered on the tooth DNA extraction process.

A biology major, Burns started in January as an intern in the biology section of the forensic laboratory of the BCA, where she assisted in finding the answers to three questions: the best method for obtaining DNA samples from uncompromised teeth, whether or not DNA could be obtained from deciduous ("baby") teeth, and whether or not DNA can be extracted from teeth that have been burned.

Burns evaluated four different methods of extracting DNA from uncompromised adult teeth to determine the method that would produce the highest DNA yield and successfully compare tooth DNA to the DNA of the tooth's donor.

Each method also was evaluated for cost effectiveness. She determined that extraction by cryogenic grinding was the best method, as the extraction protocol is quick and easy to follow, and it is comparable to the blood, saliva and sperm extraction protocols already in use in Minnesota.

In cases where a child's body is found in a suspected kidnapping or homicide case, the ability to DNA-type children's teeth would prove invaluable. Because deciduous teeth are smaller and have less root structure that adult teeth, the extraction of DNA is more difficult. Burns found that cryogenic grinding is effective with children's teeth, but more testing will need to be done before this protocol is implemented in the BCA.

In order to test whether or not conclusive results could be taken from the extraction of DNA from badly burned teeth, Burns placed 39 human teeth inside pork fillets to simulate a human jaw. With the help of the state fire marshal's staff, the fillets and teeth were put in the front and back seats of a 1983 Volvo, which burned for 50 minutes. The fire was hot enough for the aluminum wheels to melt, indicating a temperature of at least 1,000 degrees. Twenty-five of the 39 teeth were recovered from the car; it was impossible to distinguish the rest of the teeth from the other debris.

According to Burns, more testing is needed before protocols can be established for extraction from burnt teeth. Because in order to type the DNA, a tooth has to be crushed, essentially destroying it as evidence, part of Burns' task was to help determine at what point a tooth is too burned or otherwise compromised for typing. If investigators note certain physical characteristics at a burn scene, they can estimate how hot and for how long the fire burned. If they can determine that a fire was so hot that extraction would be ineffective, it may be better to save a victim's teeth for physical evidence. From her tests, Burns has determined extraction yields for both extremes: she has established that DNA yields are high when extracted from unburned teeth, and that yields are low when extracted from teeth burned at 1,200 to 1,400 degrees from 15 to 50 minutes. To define the exact point within those extremes that a tooth is too compromised to attempt DNA extraction, Burns has written a proposal outlining procedures for the BCA to use a muffle canister to burn teeth at set temperatures and time intervals.

The results of Burns' studies are now being implemented in Minnesota cases. The protocol for uncompromised teeth that she determined was most effective is currently being used in casework. The protocol for children's teeth has the potential to be utilized in kidnapping and homicide cases. The biggest contribution from Burns' work with burned teeth will come in deciding whether a tooth should be preserved for physical evidence or DNA tested to try to confirm identity.

"The most exciting part of the research to me is knowing that the results of my experiments could help identify unknown people in the future," Burns said. "The scientists around me are not working strictly for the police, they are working to figure out the truth about a potential criminal activity. I feel like I have an important part in continuing to offer the best scientific knowledge and application to the law that is presently accessible."

Burns is intrigued by the combination of investigation and science that goes into her work in the forensic lab. She likes the idea that her biological research can help solve crimes and put minds at ease. She realized the effects that her research can have when a family whose child had been murdered toured the BCA research labs.

"That's when it became real," Burns said. "Seeing the people that my work touches reminds me of what I am doing and why I am doing it."

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