Effects of Common Anticoagulants on the Visual Characteristics of Bloodstains.

Objectives: To investigate the effects of three common anticoagulants, ethylene diamine tetraacetic acid-K₂ (EDTA-K₂), sodium citrate and heparin sodium, on the visual characteristics of bloodstains such as patterns and colors.

Methods: Freshly collected blood samples were treated with EDTA-K₂, sodium citrate and heparin sodium respectively, and bloodstain samples were prepared on two objects, acrylic plate and ceramic tile. Bloodstains without anticoagulant treatment were used as the control sample. The drying time, wetting ratio, the number of cracks, the number of fragments, the central impression area ratio and the mean gray value of bloodstains were observed and recorded.

Results: Anticoagulants delayed the drying process of bloodstains. At 3.5 h, the wetting ratios of EDTA-K₂-, sodium citrate- and heparin sodium-anticoagulated bloodstains on the acrylic plate were 54.80%, 56.68% and 60.60%, respectively, which were higher than that of bloodstains without anticoagulant treatment (25.70%). Anticoagulants increased the number of cracks, the number of fragments and the central impression area ratio. The changes of these three visual characteristics were most obvious in the sodium citrate-anticoagulated bloodstains, with the crack number of 0.93/mm, the fragment number of 46, and the central impression area ratio of 48.41% after drying. Anticoagulants reduced the mean gray value of bloodstains. Among them, the sodium citrate-anticoagulated bloodstains exhibited the longest time to peak in mean gray value, reading 3.5 h. Similar changes in visual characteristics were observed on the ceramic tile.

Conclusions: The three commonly used anticoagulants change the visual characteristics of bloodstains. It is not recommended to use anticoagulated blood as a substitute for preparing experimental samples in bloodstain pattern analysis experiments. Based on the changes in the visual characteristics during the drying process of bloodstains, the time of bloodstain deposition can be roughly estimated, and the blood scene staged with anticoagulated blood can be identified.