Figure 2. Bloodstain age (TSD) correlates with a blue shift of the Hb Soret band.

Spectral profiles (350–600 nm) were obtained from samples stored at 22°C (blue diamonds) and 37°C (red squares) for 15 minutes to 1 year. The λmax_Soret is plotted as a function of stain age: A) “full range”, 15 minutes –1 year (in days); B) “hours”, 15 minutes –48 hours (in hours); C) “days”, 15 minutes –7 days (in days); D). “weeks”, 15 minutes –1 month (in days) All data points are an average of bloodstains from two biological replicates (two individual donors). The value used for each of the two biological samples was obtained from the average of three technical replicates for each sample. Using a logarithmic regression function (22°C – blue; 37°C - red), a strong degree of correlation was observed (R²>0.95 for most data sets) allowing for differentiation of deposited hours, days, weeks and months prior to collection and analysis. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article).