LECTURE 13: FINGERPRINTS // CHAPTER Flashcards
Individual characteristics
- fingerprint ridges
- tool marks
- specific paint/ surface preparations
- specific wear patterns on tires/ shoes
- material that can be fitted together to make a whole
class characteristics
- can only be associated with general type
- paint scrapings from auto accidents
- sharp, knife-like instrument
- impressions from car/truck badges
- type of can used to make a homemade explosive device
- value is that it corroborates other evidence
- place individual at the scene
- drives a particular type of car
types of prints
- fingerprints
- foot, ear, hand
- eye, iris
- tyre
- shoe
- bitemarks
- toolmarks
types of finger prints
Latent
- not visible to the naked eye
- need to use some form of visualtion technique
visible
- formed when an appropriate substance (e.g. paint, blood, ink, soot) is transferred by the finger tips to a suitable surface
plastic (or moulded)
- formed when the print is impressed into a soft material e.g. wax, chocolate, clay, fresh pain
visualising latent prints
Powders - black, gray, coloured, magnetic - used on non-porous surfaces - need to ensure contrast between powder colour and background chemicals - ninhydrin / dfo spray - lawsone - cyanoacrylate fuming - physical developer (silver nitrate AgNO3 based) spectroscopy - sometimes able to detect print directly as compounds in the print produce fluorescence - e.g. micro X-ray fluorescence combinations - typically chemical and fluorescence - becoming more common
friction rides appear on
palms, soles, ends of fingers and toes
friction ridges begind forming in
9th or 10th week of fetal development
primary friction ridge develop
develop deep in dermal layer of skin, until 15th or 17th week of gestation
secondary friction ridge develop and mature when
develop week 17 and mature week 24
loops
have 1 or more ridges entering from 1 side of the print, curving back on themselves, & exiting the fingertip on the same side.
ulnar loop
o If the loop enters & exits on the side of the finger toward the little finger
radial loop
o If the loop enters & exists on the side toward the thumbv
type lines
All loops are surrounded by 2 diverging ridges
delta
The point of divergence
core
central portion of the loop
arches
rarest of the 3
plain arch
ridges entering 1 side of the finger, gradually rising to a
rounded peak, & exiting the other side.
tended arch
arches with a pronounced, sharp peak. A pattern that
resembles a loop but lacks one of the required traits to be classified
as a loop can also be designated as a tended arch.
arches dont have
type lines, cores, deltas
whorls
have type lines & at least 2 deltas
whorls divided into 4
plain whorl, central pocket loop, double loop, & accidental
central pocket loops and plain whorls
have a minimum of one ridge that is continuous around the pattern, but this ridge does not necessarily have to be in the shape of a circle – can be an oval, ellipse, or a spiral.
plain whorls
are located between the 2 deltas of the whorl pattern
double loop
is made up of 2 loops that swirl around each other.
accidental whorls
is a pattern that combines 2 or more patterns (excluding
the plain arch) and/or does not clearly meet the criteria for any of the
other patterns.
