Forensics

Central Pocket Whorl

in these whorls, one or more of the simple recurves of the plain whorl recurves a second time.

Accidental Whorl

in these whorls, the composition of the pattern is derived from two distinct types of patterns with at least two deltas. Whorls which contain ridges matching the characteristics of a particular whorl sub-grouping are classified as accidental whorls.

Plain Whorl

in these whorls, the ridges make a turn of one complete circuit and, therefore, are circular or spiral in shape. There are at least two deltas and a ridge whose circuit may be spiral, oval or circular in shape.

Double Loop Whorl

in these whorls, there are two separate loop formations. In each of these formations, there are two entirely separate and distinct sets of shoulders and deltas.

Plain arch

pattern has a consistency of flow to it. It starts on one side of the finger, and then the ridge cascades upward slightly. The plain arch then continues along the finger to the other side. The plain arch is the simplest of the fingerprint patterns

Directionality of Bloodstains

perpendicular angle (90 degrees) => bloodstain is circular angle < 90 => bloodstain has elongated or elliptical appearance. In addition, the tail of the droplet will indicate the direction of travel of the droplet when it contacted the surface i.e the opposite direction from where the droplet originated from.

Island

short ridge segment

Tented arch

similar to the plain arch in that it starts on one side of the finger and flows out in a similar pattern to the other side. However, the difference in the tented arch lies in the ridges in the center, which are not continuous as in the case of the plain arch. The ridges, which adjoin each other in the center, converge and thrust upward, giving the impression of a pitched tent.

Blood droplets that strike a hard smooth surface, like glass, will have little or no distortion on their peripheral edges.

Surfaces such as wood or concrete will be distorted to a much greater extent, sometimes producing satellite (secondary) blood spatter droplets and stains.

How are fingerprints formed?

A person's fingerprints are formed when they are a tiny developing baby in their mother's womb. Pressure on the fingers from the baby touching, and their surroundings create what are called "friction ridges", the faint lines you see on your fingers and toes.

Enclosure

A small ridge enclosed in a "ridge pocket"

Cyanoacrylate fuming

Also self-explanatory by its name. It also reacts with moisture in the air as well as reacting with substances in the prints, forming sticky white material along ridges. Good for nonporous surfaces.

Angle of impact

Angle of Impact: The angle at which a spatter hits a surface. Formula: θ=arcsin(W/L) Where theta (θ) is the angle, W is the width of the spatter, and L is the length.

Skin layers

Epidermis: (bottom to top) stratum basale divides and pushes cells to the higher layers stratum spinosum stratum granulosum stratum licidum stratum corneum made of dead cells

Ridges

Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.

DNA Formed by

PCR

Dusting

Powder applied to prints sticks to fatty acids and lipids.

Iodine fuming

Self-explanatory by its name. It was one of the earliest methods of fingerprint development. The iodine reacts with body fats and oils in prints.

Ninhydrin

a chemical method useful for lifting latent prints on paper. It reacts with amino acids in prints.

Bifurcation

bifurcation is a point in a finger image at which two ridges meet.

Insects found at dead body

blowflies appear first (minutes or hours after death) flesh flies can arrive at similar time to blowflies usually later only maggots: died less than 24 hours ago Beetles: well after blow and flesh flies last insect left on the body Mites present with beetles initially

Spatter Patterns

created when an exposed blood source is subjected to an action or force greater than gravity (internally or externally).

Radial loop

these are loops that flow toward the radius bone of the hand or, in other words, when the downward slope of the loop is from the direction of the little finger toward the thumb of the hand.

Ulnar loop

these are loops that flow toward the ulna bone of the hand or, in other words, when the downward slope of the loop is from the direction of the thumb toward the little finger of the hand.