Abstract

The use of body fluids for source identification and event reconstruction is well-established. In recent years, the use of body fluid stains to estimate when a crime happened has been proposed. By estimating body fluid time since deposition (TSD), investigators can potentially curate a timeline of events and assess the relevance of evidence, and witness statement validity. Currently, there is no TSD method that is that is validated for forensic use. The use of molecular ecological tools to study microbial succession patterns to estimate TSD has been proposed. This systematic review summarizes, evaluates, and compares experimental conditions, methodologies, and results from 18 publications written in the past 10 years. This review is the first of its kind exploring this topic and highlights the potential forensic microbiology has for estimating the TSD of body fluids. This review also analyzed the limitations of these papers, the current gaps in knowledge, and suggested aims for future research. Results were skewed toward saliva and highlighted publications where microbial communities mapped with predefined body fluid-specific microbiomes, with potential TSD candidates. For multiple body fluids, the genera Achromobacter and Gardnerella increased in relative abundance over time in, while genera including Prevotella and Lactobacillus decreased. The results also identify major knowledge gaps on the effect of various environmental factors, such as temperature and humidity, and of substrates on microbial succession patterns and therefore body fluid TSD estimation. Molecular microbial ecological offers potential for TSD estimation in all major body fluids; however, extensive research must be carried out before it can be considered a robust predictive tool for forensic casework, characterizing microbial ecological networks, including not only bacteria.