Fingerprints, DNA fingerprints, Handwriting Analysis, Forgery

how do fingerprints form

during 10th week of pregnancy

basal layer grows faster than the epidermis layer on the outside and the dermis layer on the inside

the layer collapses and folds in on itself

arches

have ridges that enter on one side and leave on the other with a rise in the center

loops

enter from right or left and leave same way they came in

whorls

look like a bulls-eye and have two deltas

plain whorl vs. central pocket loop whorl

plain - if line drawn between 2 deltas touches center

central pocket - line doesn’t touch center

minutiae

unique ridge patterns in a person

patent (visible) prints

left on smooth surface when a liquid comes into contact with fingerprints

latent prints

prints made by transfer of oils onto a surface, not visible at first

how to collect latent prints

dusting powders or another chemical reaction, tape

plastic prints

actual indentations

left on soft material

automated fingerprint database (AFIS)

stores all of the fingerprints taken for jobs or criminal justice

it is digital so finding a match takes much less time than it used to

tented arch

forms an angle or possesses some characteristic of loop pattern like a delta

ulnar loop

opens toward little finger

radial loop

opens toward thumb

double loop whorl

2 separate loop formations

2 deltas

accidental whorl

all other prints

2+ deltas

combo of other patterns except plain

most common fingerprint pattern

loops

VNTR’s

variable numbers of tandem repeats

the number of copies of the same repeated base sequence in DNA can vary among individuals, length of a VNTR can be from 9 to 80 bases long

STR’s

short tandem repeat

short sequence of DNA (2 - 5 bases) within a noncoding DNA sequence

becoming the preferred method of analysis because small and partially degraded DNA samples may be analyzed

how can scientists increase the amount of DNA samples to use for testing

polymerase chain reaction (PCR)

3 fundamental principles of fingerprints

1. a fingerprint is an individual characteristic
2. fingerprint remains unchanged during an individual’s lifetime
3. fingerprints have a general ridge pattern that permit them to be systematically classified

basic idea of DNA fingerprinting

scientists can determine if a certain DNA sample came from a certain individual because the number and location of polymorphisms is different in everyone

main characteristics that are analyzed in handwriting

shape of letters, curve of letters, slant of letters, spacing of letters, connected letters, fully formed, i’s and t’s crossed, smoothness, margins and spacing

exemplar

known material of a person’s handwriting good for distinguishing between an unknown material

what kinds of documents can be forged

checks, employment record, wills, legal agreements and licenses

counterfeiting

false documents or other items are copied for the purpose of deception

how does US currency prevent counterfeiting

microprinting, color changing, special kind of paper, microscopic details, code

what does paper chromatography do

separates different pigments in a mixture

write a line in a certain ink, dip it in a certain solution like water or ethanol and let the colors run up the paper, almost to the top

helps to check for forgery by comparing writing utensils used