The crux of time: A meta-analysis of ex vivo whole blood degradation

Abstract

Estimating the time since deposition (TSD) of a bloodstain can provide important medico-legal information for crime scene investigation. Research in this area primarily investigates the degradation of either hemoglobin or genetic material over time. In this work, we present a comprehensive meta-analysis on bloodstain TSD research. Our results are interpreted from 25 quantitative studies used to probe the effect of biomolecule studied, analytical technique used, substrate porosity, environmental conditions, and blood source on TSD estimates. There was an overall strong effect of time across studies (Fisher’s Zr = 1.66, r = 0.93), and generally, we found that the type of biomolecule studied (e.g., hemoglobin, DNA) had equal effect sizes for TSD estimation. Differences in the mean TSD effect size were also observed between substrate porosity. Interestingly, the blood source does not significantly influence the magnitude of the effect sizes in TSD estimation. Despite the clear effect of time, forensically relevant prediction of bloodstain TSD remains complicated by inter-donor variability, type of substrate and environmental conditions. We recommend that future bloodstain TSD research increase sample size, include summary statistics and standardize experimental methodologies so that we can develop a quantitative understanding of the physicochemical processes involved in whole blood degradation in ex vivo conditions.

Rheological profiles of DNA extracts from forensic bloodstain samples

“…However, both works demonstrated that combining DNA and UV-VIS metrics generated stronger TSD models. This supports the future implementation of a combinatorial approach; rheology could be paired with a spectroscopic technique to obtain data pertaining to both DNA and protein degradation 51 .…”

“…ACD-A was made by dissolving 0.8550 g of dextrose anhydrous, 0.8448 g of sodium citric dextrose, and 0.3072 g of citric acid, all purchased from Sigma-Aldrich (Oakville, ON), to 62.5 mL of Milli-Page|7 Q® water. RNA extracted from bovine blood with and without anticoagulant has shown no significant differences in concentration or quality metrics over time, suggesting that nucleic acid extraction can be successfully performed using anticoagulated bovine blood 49 ; it has also demonstrated utility in other TSD experiments 50,51 . Bovine blood appears to have superior erythrocyte properties than other blood analogues 50,51 .…”

“…RNA extracted from bovine blood with and without anticoagulant has shown no significant differences in concentration or quality metrics over time, suggesting that nucleic acid extraction can be successfully performed using anticoagulated bovine blood 49 ; it has also demonstrated utility in other TSD experiments 50,51 . Bovine blood appears to have superior erythrocyte properties than other blood analogues 50,51 . However, there are still differences in fluid dynamics between bovine and human blood that might need to be considered 52 .…”

Elemental and molecular characterization of degrading blood pools

“…6,7 Current studies that develop predictive models for TSD typically use single drop or small volume (on the scale of µL) bloodstains. [6][7][8][9] There are many types of bloodstain patterns, we aim to explore the utility of select TSD methods to larger blood pools with different formation mechanics. 10 Whole blood is a colloidal suspension composed of solid cellular components (∼45% by volume) suspended in liquid (∼55% by volume).…”

“…6,7 Current studies that develop predictive models for TSD typically use single drop or small volume (on the scale of μL) bloodstains. 6–9 There are many types of bloodstain patterns, we aim to explore the utility of select TSD methods to larger blood pools with different formation mechanics. 10…”