This module describes forensic STR markers: mutation process, genotyping technology, and electropherogram artefacts. It reviews principles of population genetics, and measurement of relatedness. It covers general principles of evidence evaluation using LRs, computing LRs for identification using presence/absence of autosomal STR genotypes and for mitochondrial and Y-chromosome markers. The complications of mixture interpretation when the queried contributor is a relative of true contributor. The consequences of database searches. Brief discussion of probabilistic interpretation of STR profiles. New molecular techniques for human identification.