Evaluation of the M-Vac® system for DNA collection from bleach-treated blood stains: analyzing the impact of Bluestar, membrane type, and filtration

Abstract

The purpose of this experiment is to evaluate the performance of the M-Vac wet vacuum system for deoxyribonucleic acid (DNA) collection from blood-stained substrates that have been treated with bleach, a common cleaning reagent used in forensic investigations. Five variables were explored: blood concentration, bleach concentration, the presence or absence of BlueStar forensic latent bloodstain reagent, the type of membrane filter used – polyethersulfone (PES) and cellulose nitrate (CN), and the filtration product used for DNA extraction and isolation – the filter membrane itself and the filtrate. Carpet substrates were stained with single donor, whole human blood prior to treatment with bleach, which simulated cleaning the bloodstain. Appropriate samples were treated with BlueStar forensic reagent then all samples were collected with the M-Vac. The collected materials were passed over a filter with either PES or CN membrane. DNA from both the filter membranes and the filtrate were extracted, isolated, and quantified. Samples were performed in triplicate and the results, in terms of DNA quantity, underwent statistical analysis. Results indicated that the M-Vac system was capable of collecting quantifiable DNA evidence from bloodstains even after treatment with bleach. Key variances in DNA concentration between PES and CN membranes, presence and absence of BlueStar, and filters and filtrate were identified. Results demonstrated variations in DNA yield and integrity across these parameters. DNA was recovered in samples from each category of blood and bleach dilution, despite the presence of bleach. In general, BlueStar absent, CN membrane, and filter variables were found to contain higher quantities of DNA overall than their respective counterparts – BlueStar present, PES membrane, and filtrate. However, it was found that BlueStar reagent and the membrane types may have interacted with bleach or DNA extraction and quantification reagents that interfere with DNA yield. Further research is required to determine the effect these interactions may have on forensic DNA analysis with regard to quantity and quality for compromised or degraded biological samples.