forensic lab final

strip method

investigators walk from one end of the scene to the other, turn, and walk back in the opposite direction, repeating this as they get closer to the centre of the scene / area, best on large and outdoor areas

link method

based on the theory that one type of evidence leads to another item, most common, logical, experimental, systematic, works with large or small, indoor and outdoor scenes

line method

several searchers move alongside one another in one direction, moving from one end of the scene to the other, next best option if the grid method is not feasible, works best outdoors / in large scenes

grid method

modified double line search, one group of searchers moves alongside one another in one direction while another group does the same in the perpendicular direction, effective but time consuming and may not be doable if there are rocks or other things in the way, works best outdoors / in large scenes

zone method

crime scene is sectioned off into small areas, which may be sectioned off further into smaller areas, teams assigned to search each square, best in scenes with defined areas, often indoors

wheel method

several investigators start at the centre of an imaginary circle, each moves straight out in different directions (like spokes), possible to destroy evidence in the centre if care is not taken, best in small / circular scenes, limited application, used in special circumstances

spiral method

moving in a ever expanding/shrinking circle either from centre of scene outwards or perimeter of scene inwards, used to find particular items, best with scene without physical barriers, limited application

primary crime scene

the original location of the crime

secondary crime scene

any alternate location where additional evidence may be found

liquid, arson, or chemical evidence

stored in airtight, unbreakable container

large evidence

stored in clear plastic bag

dry trace evidence

stored in paper bindle, which is placed in an additional bag or envelope

wet biological evidence

stored in breathable container until dry, then treated like dry trace evidence

passive drop

falling straight down with gravity from 90º angle, produces spherical drop

spines

elongated extensions spiking out but still attached to original drop

satellites

smaller droplets the escape the cohesive original drop

elliptical drop

result from different angle of impact and show the direction of travel

direction of travel

always towards the tail

steeper the angle of impact

more elongated droplet

higher distance blood is dropped from

larger diameter of droplet

A+

anti-A: agglutination

anti-B: no agglutination

anti-Rh: agglutination

A-

anti-A: agglutination

anti-B: no agglutination

anti-Rh: no agglutination

B+

anti-A: no agglutination

anti-B: agglutination

anti-Rh: agglutination

B-

anti-A: no agglutination

anti-B: agglutination

anti-Rh: no agglutination

AB+

anti-A: agglutination

anti-B: agglutination

anti-Rh: agglutination

AB-

anti-A: agglutination

anti-B: agglutination

anti-Rh: no agglutination

O+

anti-A: no agglutination

anti-B: no agglutination

anti-Rh: agglutination

O-

anti-A: no agglutination

anti-B: no agglutination

anti-Rh: no agglutination

human cuticle

usually very smooth and scaley

animal cuticle

can either be smooth or textured and spikey

human cortex

more pigmented closer to the cuticle, colour is fairly consistent and uniform throughout the strand, can have some ovoid bodies but they are not usually as prominent if there is any at all

animal cortex

more pigment closer to the medulla, colour can vary along length of the hair, ovoid bodies are more prominent and abundant in some species

human medulla

very thin, may not even be present, can be fragmented or continuous, highly variable among an individuals hairs, thinner (usually 30% or less of the whole hair)

animal medulla

usually well defined and structured, tends to follow consistent pattern, thicker (usually 50% of the whole hair)

loop

one or more ridges enter from one side of fingerprint, curve around, and exit from the same side, must have one or more delta

arch

ridges enter from one side of finger, rise and fall like a wave, and exit the opposite side of the finger, divided into plain and tented

whorl

divided into plain, central pocket loop, double loop, and accidental. all have at least 2 deltas, plain and central pocket have at least one ridge that makes a full circuit, double loop is made up of two loops like yin and yang

dust with powders

hard, non-absortbant surfaces

flourescent powder

used with UV light on multicoloured surfaces

magnetic powder

used on shiny surfaces like plastic containers or bags

ninhydrin

chemical reaction used on latent prints on paper or cardboard

iodine

chemical reaction on latent prints that temporarily turns brownish orange, is reversible

silver nitrate

chemical reaction on latent prints on styrofoam or wood

follicle attached to hair

may be sign of forced removal / struggle, can be individual evidence with DNA analysis

gravity produced

can be pool pattern or passive drop, no other force causes shape or size

transfer bloodstains

wet bloody surface comes into contact with another surface and transfers the bloodstain there, can be wipe or swipe, both of which can indicate direction of travel

wipe transfer blood pattern

something non-bloody comes into contact with something bloody

swipe transfer blood pattern

something bloody is being moved

spatter bloodstains

blood spatter created from external force other than gravity. ex., impact spatter, cast off, arterial gush, and expired

latent print

caused by transfer of sweat, oils, or other bodily secretions on finger onto another surface