Forensic Science Bloodstain Patterns

Study Notes

Recognition of Bloodstain Patterns

Human blood composition consists of 45% cellular components (platelets, RBCs, WBCs, antibodies) and 55% fluid (water, nutrients, wastes, gases).
Blood is six times more viscous than water, and strong cohesive forces keep blood drops intact.
Vertical drops (90 degrees) create circular patterns, while angled drops result in elliptical spatters.

Surface Tension of Blood Drops

Surface texture influences the appearance of blood drops.
Smooth, non-porous surfaces (glass, tile) maintain the circular shape of blood drops.
Rough surfaces lead to irregular and spiny-edged drops due to protuberances disrupting the drop's outline.

Size, Shape & Directionality of Bloodstains

The pointed end of a blood drop indicates its direction of travel.
Area of convergence is established by drawing lines through the centers of multiple blood drops; the intersection signifies the origin point.
Area of origin refers to the location where the injury occurred, while the angle of impact illustrates the angle at which blood traveled from the body.

3-D Origin of Blood Spatter

To determine the 3-D origin of a blood spatter, position a protractor at the center of the drop and use a meter stick to measure the angle of impact toward the meter stick at the area of convergence.

Blood Spatter

Bloodstains vary randomly in distribution and size, influenced by the weapon used, blood availability, and applied force.
The characteristics of blood spatter can indicate the type of weapon involved in a crime.
Spatter found on a suspect's clothing may link them to a crime scene.
Passive spatter is characterized by drops falling straight down.

Impact Spatter

The severity of impact influences the size of blood drops produced.
Low velocity impact spatter occurs at 5 ft/second, generating drops around 4 mm in size.
Medium velocity impact spatter, arising from speeds of 5 to 25 ft/second, produces drops between 1 to 3 mm.
High velocity impact spatter occurs at speeds of 100 ft/second or more, causing misting with drops smaller than 1 mm.

Gunshot Impact Spatter

Gunshot impact creates high-velocity spatter, resulting in a mist-like distribution of blood.

Description

Explore the fascinating world of forensic science with a focus on the recognition of bloodstain patterns. This quiz covers the properties of human blood, its composition, and the behavior of blood drops. Test your knowledge on how various factors influence blood spatter analysis.