Bloodsplatter Pattern Analysis Flashcards
What are the 5 factors that affect the appearance of a bloodstain?
- The velocity at which it was travelling
- Distance travelled
- The amount of blood
- The angle of impact
- Type of target onto which it lands
What are the 9 things that a bloodstain can tell us?
- Number of blows struck during an accident
- Number of perpetrators
- Sequencing of events
- Positioning of persons within a scene
- Directionality of droplets
- Angle of impact
- Objects used (weapons)
- Force involved in the bloodshed and the direction the force was applied
- Evidence of clean up
What is bloodstain pattern analysis?
- examination of the size, shape and distribution of bloodstains and bloodstain patterns
- draws on the scientific principles of biology, chemistry, mathematics and physics
- based on the premise that all bloodstain patterns are characteristics of the forces that created them
What shape will a blood droplet take in the air?
Sphere
What is a bloodstain?
The transfer of when liquid comes into contact wth a surface or when a moist or wet surface comes into contact with dried blood
What are some locations of bloodstains?
- scene
- victim (body/clothing)
- offender (body/clothing)
- weapon
- vehicle
- furniture
- “clean up”: under rugs, linoleum, seat cushions
What is blood comprised of?
- 55% plasma: 91% water, 8% proteins, 1% organic acids/salts
- 45% proteins: 99% RBCs, 1% WBCs, 1% platelets
What are the functions of blood?
- transport
- protection
- regulation
How much of the body weight does blood account for?
8%
How much blood do males and females have?
Males: 5-6L
Females: 4-5L
How much blood loss will render someone unconscious?
1.5L
How much blood loss will result in death?
40%
What are the presumptive tests for identifying blood?
- hemastix
- luminol test
- phenolphthalein test
What are the confirmatory blood tests?
- ABA card hematrace
- Takayama test
- RSID test for human blood
Where is DNA present in blood?
Only in WBCs because RBCs lack nuclei and ribosomes
Hemastix test
- presumptive test
- looks for peroxide-like activity of haemoglobin in RBCs
- will not detect the difference between animal and human blood
- false positives: beetroot, rust, horseradish, copper, cabbage, animal saliva, past expiry date
Luminol test
- presumptive test
- luminol reacts with haematin and produces a luminescence
- false positives have been observed with the presence of copper salts (on locks, door handles)
Phenolphthalein test
- presumptive test
- presence of blood detected based upon a peroxidase reaction of haemoglobin which produces a pink colour
- false positives: saliva, pus, malt extract, vegetable extracts, the salts of certain heavy metals