We observed minimal overlap between experimental conditions for porous and non-porous substrates, especially for the analytical techniques (Table ). Mixed models aimed at understanding variation in porosity Zr values showed the fixed effects for non-porous Zr often displayed significant slopes compared to porous models. Of note, conditional R 2 values were noticeably higher -approximately 35% -than the marginal values, suggesting high interstudy variation (Table ). Fig. . Forest plot of bloodstain TSD mean effect sizes, divided by: A) substrate porosity, B) blood source, C) temperature and D) summary statistics. Piecharts are divided according to the number of effect sizes in each subgroup. Colours from the piecharts correspond to those in the forest plots. NOTE: the scale for the x-axis differs for each subgroup.