"DNA Mixtures Present Statistical Problem, Texas Labs Proactively Examining Thousands of Cases." Forensic Magazine. N.p., n.d. Web. 22 Oct. 2015.
DNA Mixtures Present Statistical Problem, Texas Labs Proactively Examining Thousands of Cases
New science makes DNA a lot more complex as it advances. One state is currently looking at thousands of cases from the last 15-plus years, making sure their analysis of identification were accurate. The Texas Science Forensic commission sent a notice out to its labs in August, notifying them that DNA mixture interpretation involving genetic material from more than one person is currently being reevaluated, based on improvements in DNA lab technology at the FBI. According to Lynn Robitaille Garcia, the general counsel for the commission, around 24,000 cases involving DNA mixtures now have to be searched through. They are trying to find out where the CPI (Combined Probability of Inclusion) fell, in terms of statistical probabilities. So when the reevaluation began, the FBI sent a notification that said they had corrected and updated their allele frequency data to all CODIS laboratories in the nation. The Combined Probability of Inclusion and Combined Probability of Exclusion have changed significantly in certain cases. This meant that a 1-in-674,000 chance of identifying a suspect's genetics could have fallen to 1-in-100. According to Professor Stephen Fienberg, there are multiple models for dealing with mixtures and they do yield different results, therefore the mixture problem is not just an issue of what tests to do in a lab, and there is not a real consensus on the ‘best’ statistical approach. Any calculation one does, should take into account there’s more than one person there.
These mixtures in DNA results could be accusing people of crimes they have never committed or maybe not even pick up DNA of the person that leads to the crime. These DNA should be read carefully so case’ have accurate conclusions.
It would have been helpful if this article gave an example of a case that had a mixture in the DNA reading, and to learn more about what happened, and what went wrong, and how they caught their mistake.
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