How is a transfer stain created?

A transfer stain is created when a blood-stained surface comes into contact with another surface. This interaction results in the transfer of blood from the original surface to the new one, leaving behind a clear impression or pattern that is indicative of the nature of the contact. For instance, if a person with blood on their hands touches a wall, the pattern of their fingers may be left behind as a transfer stain.

This mechanism differs from other processes such as pooling, which involves blood accumulating in one place without being transferred. Similarly, splashes or cast-off stains occur due to the movement of blood, typically through the force of a strike or movement, rather than direct contact between surfaces. Wiping blood away with a cloth can create smears or other types of stains but is specifically related to the action of cleaning rather than direct transfer from surface to surface. Recognition of these processes is crucial in crime scene investigations for accurately interpreting the patterns and potential sources of blood evidence.