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Blood Stain Pattern Analysis Chapter 7.2 Discussion Board 1 (Grouping…
Blood Stain Pattern Analysis Chapter 7.2
Discussion Board 1
Directionality
Direction that blood hit at impact
Angle
90-80 Degrees- Circular pattern
70-50 Degrees- Circular pattern slightly becomes more oval
40-30 Degrees- Oval pattern with small spatter tails that form
20 Degrees- Oval pattern with medium size tail
10 Degrees- Thin oval pattern with long tail
Grouping Bloodstains
Latent Stains and Tests
Leuco crystal violet- Spray
Amino black- Spray
Sprays create a permeant print
Luminol- Rust causes false positives
ABAcard HemaTrace- identify if stain is blood
Bloodborne Pathogens
People working at crime scene should assume all blood is hazardous
Hepatitis is the most common bloodborne pathogen that is contracted
PPE such as: eye protection, face mask, Tyvek suit, gloves and booties should be worne
Information Gathered about Blood Stain
Direction
Point of impact
Angle of impact
How many times victim was hit
Tools/Weapons used
Where the individuals were placed at the scene
Droplet Size and Forces
High Velocity
High force
Ex: Gunshot
Size: 1mm or smaller
Medium Velocity
Medium force
Ex: Stabbing
Size: 1-4mm
Low Velocity
Low force
Ex: Nose bleed
Size: 4mm
Types of Bloodstains
Swipes
The transfer of blood by carrying an object through blood and transferring it
Contact/Pattern Transfer
Wet blood is transferred from one object to another
Transfer Stain
Wipes, swipes and contact pattern
Latent Stain
Need a test to reveal they are present because they cannot be seen by the naked eye.
Impact Spatter
Due to impact
Spatters can be forward or backward
Other Stains
Include: projected, cast-off, and expirated
Passive Stain
Due to gravity
Ex: Bloody nose, pool of blood
Houck, Max M., et al. “Special Crime Scenes.” The Science of Crime Scenes (Second Edition), 2018, pp. 351–360., doi:
https://doi.org/10.1016/B978-0-12-849878-1.00026-0
.