Smart Forensic Phone: Colorimetric analysis of a bloodstain for age estimation using a smartphone

Estimating the age of a bloodstain is important for tracking down the true perpetrator of a crime from among the suspects. The current methods available for this estimation suffer from several shortcomings, including the time required and low accuracy. A mobile detection system, named Smart Forensic Phone, developed in this study enabled us to rapidly and precisely estimate the age of a bloodstain. We placed blood on five different materials (wallpaper, fabric, glass, wood, and A4 paper), monitored the RGB (Red, Green, and Blue) values per pixel of the bloodstain picture at 6-h intervals, and estimated the approximate age of the bloodstain using a smartphone application. The RGB values were converted into the V value of HSV (hue, saturation, and brightness). A rapid decline in RGB and V values was observed over the first 42 h and thereafter remained relatively unchanged. The age of the bloodstain could be calculated from the plot of V vs. time. This method enables the estimation of the age of the bloodstain if it is less than 42 h old. We will be continuing to work toward optimizing the method, so that the age of the bloodstain older than 42 h can be determined using the Smart Forensic Phone. Our detection system offers a novel method to both criminal investigators and researchers for predicting the time elapsed after the victim's death, which is also called postmortem interval (PMI) or the approximate time when the crime was committed.