Human bloodstains on biological materials: high-vacuum scanning electron microscope examination using specimens without previous preparation.

Studies of human bloodstains on nonbiological materials have been previously carried out using a high-vacuum scanning electron microscope (HV-SEM) in secondary-electron mode without any sample treatment. To assess whether biological substrates can affect the morphology of human erythrocytes in bloodstains, three fragments of different biological material (bone, shell, and wood) were smeared with peripheral human blood. Afterward, the bloodstains were directly examined in secondary-electron mode by an HV-SEM following a procedure initially standardized to be used in uncoated human bloodstains on stone. The obtained results suggest that HV-SEM is suitable for examining untreated bloodstains on biological substrate and that the morphology of erythrocytes in human bloodstains is not affected by the biological nature of the substrate. A cautionary issue regarding bloodstains on nondehydrated biological substrates is that the waiting time required for initiating the HV-SEM examination is by far higher than when using inorganic bloodstain substrates.