Beyond traditional paternity and identification cases Selecting the most probable pedigree

The paper extends on the traditional methodology used to quantify DNA evide nce in paternity or identification cases. By extending we imply that there ale more than two alternatives to choose between. In a standard paternity c ase the two competing explanations H-1: "John Doe is the father of the chil d" and H-2: "A random man is the father of the child", are typically consid ered. A paternity index of 100 000 implies that the data is 100 000 more li kely assuming hypothesis H-1 rather than H-2. If H-2 is replaced by "A brot her of John Doe is the father", the LR may change dramatically. The main to pic of this paper is to determine the most probable pedigree given a certai n set of data including DNA profiles. In the previous example this correspo nds to determining the most likely relation between John Doe and the child. Based on DNA obtained from victims of a fire, bodies found in an ancient g rave or from individuals seeking to confirm their anticipated family relati ons, we would like to determine the most probable pedigree. The approach we present provides the possibility to combine non-DNA evidence, say age of i ndividuals, and DNA profiles. The program familias, obtainable as shareware from http://www.nr.no/familias, delivers the probabilities for the various family constellations. More precisely, the information (if any) prior to D NA is combined with the DNA-profiles in a Bayesian manner to deliver the po sterior probabilities. We exemplify using the well published Romanov data w here the accepted solution emerges among 4536 possibilities considered. Var ious other applications based on forensic case work are discussed. In addit ion we have simulated data to resemble an incest case. Since the true famil y relation is known in this case, we may evaluate the method. (C) 2000 Else vier Science Ireland Ltd. All rights reserved.