Forensics Quiz
anagen stage
- Active growing stage of hair (cells rapidly dividing and depositing materials within the hair) - lasts approx. 1000 days - 80-90% of human hair is in this stage
catagen stage
- brief transitional stage of hair growth when all cell division stops - follicle recedes as the blood supply is reduced - 2% of all hair growth/development
animal hair v. human hair
- differ in pattern of pigmentation, medullary index, and cuticle type - medulla is proportionally thicker than in humans - medullary index > or equal to 0.5, it is animal hair - medullary index < or equal to 0.33, it is human hair
European hair
- generally straight or wavy - small and evenly distributed pigment granules - cross section: oval or round of moderate diameter with minimal variation - color may be blond, black, red, or brown
why is bleached/dyed hair easy to identify?
- it lacks pigment in the cortex and cuticle - changes color of hair shaft and gives it easily recognizable painted appearance - if an entire hair is recovered, experts can discover when the hair was last color-treated
African hair
- kinky, curly, or coiled; shaft may be buckled - pigment granules: densely distributed, clumped, may differ in size and shape - cross section: flattened with moderate to small diameter and considerable variation
Asian hair
- straight - densely distributed pigments - cross section: round with large diameter - shaft tends to be coarse and straight; thick cuticle; continuous medulla; color black
telogen stage
- the final or resting phase in the hair growth cycle - follicle becomes dormant - 10-18% - at the end of this stage, the blood supply reconnects to the follicle and the anagen stage begins again
phase contrast microscopy
- uses special objective lens and special condenser with a compound microscope - focuses light that passes through objects at different angles
six types of hair on human body
1. head 2. eyebrows and eyelashes 3. beard and mustache 4. underarm 5. body 6. pubic
how fast does human hair grow?
1.3 cm per month (0.44 mm per day)
Gas Chromatography
Test on hair that can identify and quantify drugs, toxins, heavy metals, and even assess nutritional deficiencies.
Which of the following characteristics is found in typical asian hair?
Dark medulla
what are the three ancestrally significant groups associated with hair?
European, Asian, and African
T/F Hair is composed mostly of protein called cellulose
False
T/F To determine blood type, Luminol is added to blood
False
T/F all hairs on the head of a person are identical
False
Secondary transfer (Locard's Principle of Exchange)
The transfer of evidence such as a fiber from a source (for example, a carpet) to a person (suspect), and then to another person (victim).
T/F Hair can provide clues about someone's ancestry
True
T/F blood spatter on a wall in a series of rising and falling arcs is often caused by a severed artery
True
T/F blood-typing evidence is now used more to exclude a suspect than to identify a suspect
True
T/F The shaft of the hair is considered class evidence in a trial
True (gives only color of hair)
Wipe blood-spatter stains
a pattern that is created from an object moving through a partly dried bloodstain
isotope analysis
a technique that helps provide a timeline of a person's movements through a strand of hair
What can hair be used to determine?
diet, drug habits, and geographic history
how to find number of months since drug use?
divide length of hair at which toxin was found by 1.3
how can we estimate when hair was last colored?
dividing hair length by 1.3
imbricate
flattened, overlapping scales commonly found in human and in many animal hairs
Which part(s) of a hair can be analyzed for nuclear DNA?
follicle
Animal hair can be distinguished from human hair because animal hair _________________
has a greater medullary index and more variation in the cuticle patterns
Human hair has which type of cuticle?
imbricate
cortex
largest part of the hair shaft; contains the most melanin granules that give the hair its color
electron microscope
microscope that forms an image by focusing beams of electrons onto a specimen
how is hair first examined?
microscopically
Type O blood
no antigens but does have A and B antibodies
What is the most likely result of hair bleaching?
oxidized hair and damaged DNA
Spine and satellite
spine is sharp, splendor, and often-pointed projection, while blood satellites are small secondary drops
Although variations can occur, what best describes European hair?
straight or wavy with evenly distributed granules
The period when hair is naturally shed is called the _____________ stage
telogen
Blood Adhesion
the attraction between molecules of different substances
Blood cohesion
the attraction between molecules of the same substance
medulla
the central core of a hair
Type AB+ blood
Contains the A antigen, B antigen, and the Rh factor on the surface of RBCs
fluorescence microscopy
uses a fluorescent dye that emits fluorescence when illuminated with ultraviolet radiation; indicates dye on hair
how many hairs are usually collected from a suspect/victim's head?
50 (to prevent inconsistencies)
The Structure of Human Hair
A hair consists of two parts: a follicle and a shaft. The follicle, a club-shaped structure, contains cells with DNA and nutrients. The hair shaft is composed of the protein keratin, which is very strong and resistant to decomposition (making it very useful to forensic scientists).
What is needed for hair to be evidence?
A hair must have the follicle and its nuclear DNA, or genetic material in its nucleus, or it cannot provide individual evidence. Mitochondrial DNA (mtDNA), which is inherited from the mother, can reveal some of suspect's or victim's family relationships. Physical examination of hair, however, can provide class evidence.
The hair shaft
Made up of three layers: an inner medulla, a cortex, and an outer cuticle
Swipe blood-spatter stains
the result of a bloody object in motion that comes into contact with another clean surface
Which factors are used to calculate the medullary index of the hair?
the width of the medulla and width of the hair
What is microscopic hair analysis used for?
to exclude a suspect
cuticle
transparent outer layer of the hair shaft; made of scales that overlap one another and protect the inner layers of the hair