Variability in health risks among individuals with Down syndrome suggests the possibility of underlying polymorphism on chromosome 21 that is responsible for the variation in risk. Inference of association between risk and SNPs can be improved with haplotype information, motivating the problem of solving haplotype phases in the case of trisomy. Any gene on chromosome 21 in a Down patient will have the haplotypes of the three copies of chromosome 21 confounded. A variety of methods including EM and Bayesian analysis have provided useful solutions for haplotype phasing of disomic genotypes. Here we provide an extension to the Bayesian approach for inferring linkage phase in trisomic samples.