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Networks Knowledge Helps Solve Anthrax Killer Mystery


In 2001, shortly after the September 11th terrorist attacks, the United States faced another scare: the anthrax killer. Although the number of people physically affected by the anthrax attacks was low (5 people were killed and 17 people were harmed), the method and targets of the attacks were enough cause for scare. As the article explains, the anthrax killer sickened people with anthrax laced letters sent in the U.S. Mail, and targeted the U.S. Capitol along with news agencies in New York and Florida. Since the letters were sent with high quality anthrax and contained mixed Arabic and English messages, the FBI turned to its very own biotech industry to search for the suspect.

After e-mailing over 4,000 biologists in the American Society for Microbiology, a response from Nancy Haigwood caught the FBl’s eye. She suspected that a former colleague, Bruce Ivins, was behind the attacks after receiving an e-mail from him containing photos of him handling anthrax without gloves. Ivins was an anthrax expert working for the U.S. Army Medical Research Institute for Infectious Diseases. Haigwood knew Ivins from her years as an undergraduate student because he had a disturbing obsession with the sorority that she was a part of at the University of North Carolina. At first, the FBI did not know how this lead played into their investigation, but as time went on, more clues linking Ivins to the crime appeared. However, Ivins died of a drug overdose in 2008 just before the FBI was about to press charges, and he was never prosecuted. Confident that Ivins was the anthrax killer, the FBI closed the case in 2010.

The crime solving skills used to solve the mystery of the anthrax killer are a great application of the properties of networks. When the FBI sent out an e-mail to the American Society of Microbiology looking for information on the anthrax killer, the agency was relying on strong triadic closure to help solve the case. Strong triadic closure is a principle that if one person is strongly linked to two other people, there is increased likelihood that the two other people will have a connection. The FBI was looking for someone in the Society to provide the link between them and a suspect. Nancy Haigwood was the missing person needed to provide closure. The FBI had strong connections to suspects as well as people who could possibly have knowledge of a criminal within the Microbiology community. The FBI then had increased likelihood of finding the villain, because according to strong triadic closure, there had to be a link between the two groups.

Additionally, this article shows how balanced networks exist and can be helpful in fighting crime. A network is balanced when there are all positive connections between three people or there is one positive connection amongst two other negative connections. In this scenario, there was a negative connection between Haigwood and Ivins due to previous attacks against her and her sorority. Additionally, there was a negative connection between the FBI and Ivins because Ivins was the criminal which the FBI wants to find. However, a positive connection existed between the FBI and Haigwood because Haigwood was willing to provide information to the FBI out of her concern for national safety. It could then be said that the FBI used the properties of balanced networks to also help solve the crime. If the FBI assumed that a balanced network existed, then it was more probable that they would find the mutual enemy amongst people working towards the greater good of society. The use of these strategies by the FBI shows how network knowledge is a great partner in solving crime.


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October 2011