impression evidence exam 1

what are the outer five layers of the skin called

epidermis

what is keratin and where is it found

it provides structure to cells to keep them from breaking; it’s found in the epidermis

what are the inner two layers of the skin called

dermis; papillary and reticular layers

what is the structure of the hypodermis

loose connective tissue

what is the basement membrane of the skin called and made of

stratum basale; made of generating layer, one cell thick

what sweat glands are found on the hands and feet (ridges of skin)

eccrine

what sweat glands have the highest concentration

eccrine

what sweat glands are found on hair follicles

apocrine

what are the oil glands found in hair follicles called

sebaceous

what materials do eccrine glands sweat

98% water and 2% solids; half inorganic salts and half organic compounds

what layer do cells start and how long does it take for them to reach surface

basal layer; take 30 days, migrating at an even rate

what are permanent scars

adherence of epidermal cells to each other, attachment of epidermis to basement membrane, attachment of basal membrane to dermis

when do volar pads develop

during 6th week of fertilization; hands appear as a paddle

when do fingers begin to separate, thumb rotates into position, and creases appear

during 10th week of fertilization

when do pads regress and ridges to take shape

11th week of fertilization

what characteristics determine pattern type

timing, size, position, and individual pressure

what patterns do low volar pads tend to form

arches or low count loops

what patterns do high centered pads tend to form

whorl patterns

what do intermediate pads tend to form

loops

when do permanent, consistent patters tend to form

during 19th week of fertilization

what are flexion creases

white lines seen on the surface of handprint; genetically controlled and formed at same time as ridges; ridges run through temporary ones

how many minutiae are compared out of a total of how many

16 out of about 150 points are looked at

what is a latent print

hidden or invisible prints typically formed by transfer of sweat or oil from finger when touching surface; usually require enhancement to see

whhat are patent prints

visible to the naked eye, but less common than latent and typically make by fingers coated in foreign substance

what are plastic prints

3D impression made on pliable surfaces like putty, butter, candles, etc.

what percentage of prints have arches

5%

what percentage of prints have loops

60-65%

what percentage of prints have whorls

30-35%

what is a plain arch

gentle rise in the center of the pattern

what is a tented arch

more pointed rise in the center of pattern

what types of prints are usually found at crime scenes

partial prints

what is the most common method for identification of latent prints

powders; usually black and silver

how is iodine used as a print identification method

undergoes sublimation

how is superglue used as a print identifier

dissolves in oils of the print to form visible white ridges; very sensitive

what is the traditional approach to a body at the scene

photograph position and condition of body, “bad” hands, place in body bag, move to ME’s office, see what evidence may be collected from body

what processing techniques should be used first

the least intrusive and desctructive

what is “in situ” processing

data collection at the crime scene; it’s better to recover fragile evidence and estimate time since death; may require systematic visual examination

what evidence might you find at the crime scene

friction ridge detail, pattern transfers, trace elements, biological elements, gunshot residue