George R. Carmody
Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada

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DNA evidence is widely used as transfer evidence, where it can establish a link between a suspect and a crime scene or victim. Unlike other forensic transfer evidence however, DNA can also be used to establish relatedness to a family in cases where a person is missing and there is no standard sample available for comparison. The weight of this evidence can be measured by calculating a ratio between the conditional probability of observing the DNA evidence if the person was a member of a family pedigree to the conditional probability of observing the evidence when the source was a random person from the relevant population. I will go through the logic of doing these kinds of calculations and will illustrate their use in actual casework examples.