Figure 2 . Topographical scans of the right side of a 4 µL bloodstain. Scans were taken every 5 minutes after deposition up to 120 minutes. Scans of the 11 µL and 20 µL bloodstains can be found in Figures S1 and S2 of the supplemental.
A correlation matrix was used to assess the relationship between each surface characteristic in the short-term experiments. RMS roughness and surface roughness were found to be highly correlated (r = 0.99). RMS roughness was also found to have a greater correlation with maximum height (r = 0.93) compared to surface roughness (r = 0.89); therefore, surface roughness was chosen for data interpretation. Some early data points were not included, as sections of the bloodstain were still liquid and could not be accurately measured by the profilometer, particularly in the larger blood volumes. Each volume of blood displayed similar general trends for each surface characteristic assessed, with differences between timepoints scalable to the volume of blood used (Figure 3).