Unit 4-Physical Evidence: Hair, Blood, & Fingerprints Flashcards
Has there been a way found to individualize hair?
No, you can’t match hair to a particular person through its morphology.
Morphology
Hair’s form and structure.
Is hair different as we age, or on doc parts of the body?
Yes!!!
Where are hair sample generally taken from?
Head or pubic area.
How much hair is collected from the scalp?
50 strands of hair.
How much does hair grow each month?
1 inch
How much of the strand of hair should you collect?
Pull out at scalp/ skin line to see variation in colour/structure.
How do you determine if hair is human or animal?
Look for the presence or absence of a medulla.
Medulla
Set of cells that run through a hair.
Is DNA testing more accurate than microscope analysis?
Yes, in a study it was 10% more accurate.
Where do you extract Nuclear DNA from?
The follicular tissue and root of hair.
Nuclear DNA
Found in the nucleus of a cell and is inherited from both biological parents. Produces individualized results, harder procedure.
Mitochondrial DNA
Found in small structure outside the nucleus of a cell and is inherited from the biological mother. Only produces class characteristics, easier procedure.
Analysis of blood began when, and by who?
Began in 1901- Karl Landsteiner discovered the categorization of blood into types.
A-B-O System
Categorized the properties of blood into 3 different blood types.
When was the Rh factor discovered?
In the 1930s, established many blood groups within the overall system.
Kastle Meyer color test
Mixes a sample of dried substance with the chemical phenolphthalein and hydrogen peroxide. Used to determine if a substance is blood or not.
Hemoglobin
A protein which transports oxygen and gives blood it’s red colour.
Luminal Test
Luminol reagent sprayed to see it blood is present.
Luminol
Very sensitive test, can show blood even when diluted up to 300,000 times.
Precipitin Test
Used to distinguish between animal and human blood. Requires a small amount of blood and useful on dried blood that’s 10-15 years old.
Herbert L. MacDonell
Studied bloodstains and has offered many important observations about blood stains.
How do you know the direction blood is travelling in?
Pointed end is the direction it was travelling.
How to determine where a victims was standing when shot?
Construct straight line from individual blood spatter, they meet where person was standing.
How many ridge characteristics in each fingerprint?
150.
How many points are look for at minimum when analyzing a fingerprint.
8-16.
Loop fingerprints.
Ridge lines that enter on 1 side, loop around and exit on the same side. 60-65% of the population.
Whorl fingerprints.
Have ridge patterns that are circular on shape with 2 deltas. 30-35% of the population.
Arch Fingerprints
Ridge lines that start on 1 side and exit on the other side of the print. 5% of the population.
Latent Fingerprints
Made by the oil and perspiration that is deposited on a surface when we touch it. Invisible to the naked eye.
Visible Fingerprints
Created when a surface is touched after the finger has been in contact with another substance.
Plastic Prints
Prints created when the finger touches a soft material like soap/putty.
Device that aims UV lights at areas where fingerprints may be. Reflect light back if fingerprint is there.
Reflected Ultraviolet Imaging System.
