Stutter is an artefact seen when amplifying short tandem repeats and typically occurs at one repeat unit shorter in length than the parent allele. In forensic analysis, stutter complicates the analysis of DNA profiles from multiple contributors, known as mixed profiles, a common profile type. Consequently it is important to both understand and predict stutter behavior in order to improve understanding of the resolution and interpretation of these profiles. The authors used synthetic oligonucleotides comprising multiple repeat units to test the influence of repeat number, the influence of repeat sequence, and the impact of interruptions to the repeat sequence length. Using multiple replicates allows detailed statistical analysis. The study confirmed a linear relationship between stutter ratio and repeat number. The study shows that increased A-T content increases stutter ratio and that interruptions in repeating sequences decreased stutter ratios to levels similar to the longest uninterrupted repeat stretch. The authors also found that there was no relationship between stutter ratio and repeat number for a repeat unit with an A-T content of 1/4 and that half of the interrupted repeat sequences stuttered significantly less than their longest uninterrupted repeat stretches. The study applied the knowledge gained to examine specific features of the loci present in the AmpFlSTR() SGM Plus() multiplex kit used in the laboratory. (Published Abstract)