In many ways, DNA profiling has served as the poster child for attaching statistical calculations to forensic evidence. It is the offense level propositions that are of interest to a court, whereas it is the source level that can be addressed by the forensic analyst. The source level propositions have been further divided, in Taylor et al. Most current forensic DNA profiles consist of the genetic constitution, or genotype, of a sample or a person at up to 20 individual positions in the human genome. At each of these positions a person has material, or an allele, from each of their two parents so that the profile is a set of 20 pairs of allele types. Situations in which some of the alleles in the evidence profile may be masked by typing artifacts such as stutter or may have dropped out completely and are not detected have been discussed in Gill et al.