Estimating Time since Deposition of Bloodstains by Scanning Electrochemical Microscopy

Abstract A novel strategy has been developed for determining the time since deposition (TSD) of bloodstains on poly (vinylidene difluoride) (PVDF) membrane using scanning electrochemical microscopy (SECM) in the surface interrogation mode. In this approach, the estimation of elapsed time was based on the changes of tip current depending on the reaction between the tip‐generated reductant [Ru(NH 3 ) 6 ] 2+ and hemichrome (HC) formed during bloodstain aging. Lateral scanning results of bloodstains with two timelines (4.5‐61 h and 2–144 h) were analyzed to establish a current‐TSD aging fitting curve for providing quantitative predictions. The results indicate a high correlation between tip current and TSD of a bloodstain. Finally, this method was effectively expanded to differentiate blood fingermarks (BFMs) between 3.5+1.5 h and 75.5+1.5 h, which was very helpful to establish the relevant association of multiple bloodstains. It shows the great promise for practical use in the dating of BFMs or bloodstains.