FORS-2107EL Study Guide - Final Guide: Respiratory Arrest, Cysteine, Ower
27 Jun 2018
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1. Blood stain
-Drop Size ( ↑ heigh/ ↑ volume = ↑ drop)
-The larger the height/volume, the larger the drop size
-Satellite drops are more present in higher distance drops because the terminal
velocity of the drop allows for the surface tension of the blood to be exceeded in
the dispersion stage of impact
-The smaller the source of blood, the smaller the volume and the smaller the drop
sizes
-Size Texture ( smooth = rounder, rough = elliptical & more spatter)
-The type of surface on which a bloodstain lands on will have a different
appearance, based on the smoothness/texture of that surface and how the blood
may be absorbed treated when it comes into contact with the surface
-Smooth surface:
-Less satellite, spattering and spines
-Rounder drops
-Rough surface:
-More satellite, spattering and spines
-More elliptical shaped drops
-Impact Angle ( ↑angle (upto 90) = more circular, measured from the ground up)
-The smaller the angle (measured from the ground up), the more elliptical the shape
of the drop
-A larger angle (up to 90 degrees) created a more rounded, and less elliptical drop
-The tail on the drop (dot on the !) will point to the direction of movement
-Bloodied Object
-Depending on the amount of blood present on the object, and where the blood falls
on the object, the appearance of the object can be determined (eg. meat mallet,
hammer, etc)
-Cast off Pattern ( ↑object = ↑drop sizes) (# of blows = line strands +1)
-Cast off patterns are unique in the sense that they are caused by centrifugal force,
making an arced pattern
-It is possible to narrow down objects as the source of the blood based on their size,
this is because in cast off pattern there is a higher volume of blood on larger
objects (ex. bat vs knife), which will allow a larger volume of blood to accumulate
on the weapon and larger drops to form in the cast off pattern
-Cast off will form elongation patterns which will allow us to see the number of blows
that were delivered to the wound
-# of blows = line strands +1 (due to the first blow just breaking the skin but not
causing any blood to be expelled until the second blow)
-Directionality of Passive Drops (spines point in direction of travel, walking more
circular & less spatter and satellites)
-While walking, the drops were mostly round, also small spines that appeared when
walking, which will point to the direction of travel
-Running made the shape much more elongated, and the spines in the drops were
much more pronounced to point in the direction of travel, as well as satellites
getting larger and more common
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2. Ballistics
-Background
-Handguns (revolvers, semi automatic pistols), shotguns, rifles
-The cartridge contains a powder (propellant), a projectile (bullet), a primer cap that
will be struck by the firing pin and a case to hold all the components together.
-Pistols, revolvers, and rifles have rifled barrels which will twist the projectile
as it travels down it, which allows the bullet to travel further in a straight line, and
will leave rifling marks on the bullet
-Shotguns and some rifles do not have this twist and travel down their barrel
smoothly, therefore they have shorter flight paths and won’t go as far in a straight
line.
-Semi-automatic pistols are the weapons of choice by law enforcement, as they are
more capable then revolvers, as they are easy to reload and conceal
-Semi autos have a moving slide action that will load cartridges into the firing
chamber, which are supplied through a removable magazine
-The magazine is inserted through the bottom of the pistol
-In casings:
-we can look for microscopic changes that are tiny scratches and dents in the
casings
-the breach face has manufacturers stamp/info as well as the caliber of the
cartridge
-can look to see if the dent in the primer cap was well entered or closer to the
edge
-In bullets:
-we look for rifling marks
-the amount of twist, and whether it went right or left
-the number and width of the lands and grooves
-the amount and type of microscopic changes depend on what ammunition was
fired and how frequently the gun was discharged
-For analysis, low power microscopes and comparison microscopes are used
-The breach face of a casing has markings from the firing pin impressions, and the
manufacturer’s mark and caliber
3. Footwear
-Footprints are the second most common type of evidence type, after DNA
-A positive impression is 2 dimensional, and occurs when someone transfers matter (like dust
or blood) from their shoe to the surface they walk on
-A negative impression is 3 dimensional, and occurs when the shoe removes residue from the
surface it walks on (ex. mud or cement)
-Class characteristics: brand, make, outsole pattern, design features, size, which all help to
find the manufacturer of the shoes
-Individual characteristics: manufacturing irregularities, holes in tread, wear on the shoe, rocks
can make holes and indentations
-Wear patterns occur from gradual wearing away of rubber due to friction between the surface
the sole of the shoe
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Drop size ( heigh/ volume = drop) The larger the height/volume, the larger the drop size. Satellite drops are more present in higher distance drops because the terminal velocity of the drop allows for the surface tension of the blood to be exceeded in the dispersion stage of impact. The smaller the source of blood, the smaller the volume and the smaller the drop sizes. Size texture ( smooth = rounder, rough = elliptical & more spatter) The type of surface on which a bloodstain lands on will have a different appearance, based on the smoothness/texture of that surface and how the blood may be absorbed treated when it comes into contact with the surface. Impact angle ( angle (upto 90) = more circular, measured from the ground up) The smaller the angle (measured from the ground up), the more elliptical the shape. A larger angle (up to 90 degrees) created a more rounded, and less elliptical drop.
