As the phenomenon is observable with the naked eyes, we
expected the color change to be quantitatively detectable in a
digital image of the bloodstains. A digital image is formed when an
image sensor converts reflected light that has passes through three
color filters – red, green, and blue (RGB) – into digital signals. The
intensity of the RGB values determines the final color of each pixel
(the smallest element in a display device). We hypothesized that
these values and their counterparts, e.g. cyan, magenta, yellow, and
key (CMYK), can be plotted against time since deposition to
generate a calibration curve; subsequently, the time since
deposition of unknown samples can be determined by comparing
their color values to the calibration curve. A similar process has
been used to correlate the color change of chicory to storage time
[14], as well as to determine the concentration of amphetamine,
methylamphetamine [15], and trinitrotoluene (TNT) [16,17].