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DNA - A Prosecutor’s Practice Notebook Inventory

The Probability of Exclusion

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The probability of exclusion calculation is helpful in interpreting mixtures. This calculates the percentage of the population that can be excluded as contributors to the collected evidence and can assist the jury in understanding what the DNA mixture means. If the suspect is included as a possible contributor, this calculation will state how large the group of possible contributors is.

Due to the power of STR typing, a DNA mixture will almost always exclude a huge percentage of the population as possible contributors to the mixture. For example, in such a case the probability of exclusion calculation may state that 00.99952% of the population would be excluded as a possible contributor.

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