Figure 3. Average values (n=3) for surface average roughness
(µm), maximum height (µm), skewness, and kurtosis of the right side of
degrading bloodstains of various volumes at varying time points after
deposition. Inlet images show topographical scans from 4 µL bloodstain
(stain #2), 11 µL bloodstain (stain #1) and 20 µL bloodstain (stain
#1) at 10 minutes and 120 minutes after deposition.
As the bloodstain desiccated, the surface average roughness decreased
until approximately 20 minutes, and then increased slightly until
plateauing at about 35-40 minutes (Figure 3, d). The maximum height of
the bloodstains typically decreased until 20 minutes, which remained
consistent until 120 minutes (Figure 3, b). A sharp decrease in height
occurred as the bloodstain began to flatten out, and the rise around
~15 minutes corresponded with the formation of the RBC
‘donut’ (Figure 3). This trend was more difficult to confirm in the
larger volumes of blood due to the lack of time points prior to 10
minutes. Kurtosis increased until approximately 20 minutes, and also
plateaued at about 40 minutes (Figure 3, a). Interestingly, 11 μL
displayed the greatest kurtosis values at almost every time point in the
short-term experiments. The skewness values decreased up to 20 minutes,
before increasing up to 40 minutes, where the values then plateaued
(Figure 3, c). Similar to the kurtosis trends, the 11 μL bloodstains had
higher relative skewness values. Kurtosis and skewness displayed
opposite trends within the first 40 minutes, which was corroborated by
the correlation coefficient (r = -0.70). Lastly, height
distributions for the short-term experiments were assessed. The height
of the bloodstain was higher at earlier time points and decreased
sharply around 25-30 minutes (Figure 4). Interestingly, we observed
variance in size distributions between volumes and replicates, with the
maximum frequency ranging between approximately 30 – 60 µm.