Blood Patterns
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Transcript of Blood Patterns
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Blood PatternsForensic Science
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A Brief Intro to Blood Spatter Analysis
• Blood contains DNA, so it is possible to identify its exact source.
• The shape of the spatter indicates:1. the point of origin2. direction of travel, and 3. angle of impact.• Certain chemicals can detect the
presence of blood even when it is not visible
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BLOOD TYPES• Four types of blood- A, B, AB, O
Type A contains the A proteinsType B contains the B proteinsType AB contains both A & B proteinsType O contains neither A nor B
proteins
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The Rh Factor• This is the + or – after the blood
type
A+, A-, O+, O-…and so on.
+ means the Rh protein is present, - means the Rh protein is absent
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BLOOD COMPATIBILITY• Type O- is the universal donor- all
other blood types can accept type O blood
• Type AB+ is the universal recipient- it can take all other types of blood
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MORE ON COMPATIBILITYType O+: takes O- or O+Type O-: takes O-Type A+: takes A+, A-, O+ or O-Type A-: takes A- or O-Type B+: takes B+, B-, O+ or O-Type B-: takes B- or O-Type AB+: takes A+, A-, B+, B-, AB+, AB-, O+,
O-Type AB-: takes A-, B-, AB-, O-
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Basic Info on Shapes of Drops
• The “tail” points in the direction of travel.
• Drop at 90 degree angle will be circular.
• Drop at less than 90 degree angle will be elliptical
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PRESERVING BLOOD EVIDENCE
• Never place bloody evidence in plastic…it could promote mold growth and destroy the sample.
• Blood soaked evidence should be placed in paper.
NEXT: EXAMPLES OF BLOOD SPATTERS
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Arterial Blood
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Cast Off
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Drip
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Flow Pattern
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Hair Pattern
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Low Velocity
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Medium Velocity
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High Velocity
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Swipe Pattern
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Transfer from Hammer
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Transfer from Screwdriver
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Transfer from Fingers
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Transfer from Footwear
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Transfer from Knife Blade
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Wipe from Drying Blood Drop
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The End
References:Forensic Science: An Introduction to
Scientific and Investigative Techniques by Stuart H. James & Jon J. Nordby
Images from www.peelpolice.on.ca