10.26091/ESRNZ.11375766.v1 Jo-Anne Bright Jo-Anne Bright Kate Stevenson Kate Stevenson James M. Curran James M. Curran John S. Buckleton John S. Buckleton The variability in likelihood ratios due to different mechanisms Institute of Environmental Science and Research 2019 Forensic DNA Interpretation Likelihood ratio Markov Chain Monte Carlo techniques MCMC STRmix™ Genetics Gene Expression (incl. Microarray and other genome-wide approaches) Forensic Biology 2019-12-18 03:29:04 Journal contribution https://research.esr.cri.nz/articles/journal_contribution/The_variability_in_likelihood_ratios_due_to_different_mechanisms/11375766 Recently there has been a drive towards standardisation of forensic DNA interpretation methods resulting in the uptake of probabilistic interpretation software. Some of these software solutions utilise Markov chain Monte Carlo techniques (MCMC). They will not produce an identical answer after repeat interpretations of the same evidence profile because of the Monte Carlo aspect. This is a new source of variability within the forensic DNA analysis process. In this paper we explore the size of the MCMC variability within the interpretation software STRmix™ compared to other sources of variability in forensic DNA profiling including PCR, capillary electrophoresis load and injection, and the makeup of allele frequency databases. The MCMC variability within STRmix™ was shown to be the smallest source of variability in this process.