Julia Mortera: Probabilistic Expert Systems for Forensic Identification

Problems of forensic identification from DNA profile evidence can become extremel challenging, both logically and computationally, in the presence of such complicating features as missing data on individuals, mutation, mixed trace evidence, laboratory contamination and artifacts as well as violations of standard assumptions about founding genes. In recent years it has been shown how object-oriented Bayesian networks can be used to represent and solve such problems. This architecture proves particularly natural and useful for complex forensic identification problems. I will describe a "construction set" of fundamental networks, that can be pieced together, as required, to represent and solve a wide variety of problems arising in forensic genetics. Probabilistic expert systems can be used to analyse forensic identification problems involving DNA mixture traces using peak area information. This information can be exploited to make inferences regarding the genetic profiles of unknown contributors to the mixture, or for evaluating the evidential strength for a hypothesis that DNA from a particular person is present in the mixture. We illustrate the use of the networks on published criminal casework examples.