Crime Scene Final Exam

Basic elements needed in a sketch

Basic elements needed in a sketch

Heading, illustration area, legend, title block, scale

Tools needed to create a sketch

graph paper, pencil, rule/scale, scanner or total station

What is the purpose of a sketch or diagram?

give the jury a birds-eye view of the scene

T/F: everything inside a crime scene should be measured

False

What should be measured in a crime scene?

dimensions of the room, placement of the body and other relevant evidence or structures (windows, doors, etc.)

Methods of crime scene mapping

Rectangular coordinates and triangulation

What details should be included in the beginning of your report

Should detail how you came to be involved in the investigation (the briefing)

Characteristics of a scene

physical description of the scene

Conditions of the scene

things that can be changed (environmental conditions, was it secured, things that may not have been there before officers arrived)

Do we include facts or opinions when writing our reports?

We deal in facts

Is there ever a time when we render our opinions?

In reconstruction cases (bullet trajectory or blood spatter analysis), but they must be based in fact and come from an expert on the topic

Organization of a report

how you came to be involved in the investigation, detail conditions & characteristics of the scene, detail the facts of the scene

What does BPA focus on the analysis of?

the size, shape, and distribution of blood stains from a bloodshedding event

When measuring spatter stains, do we look at the length or width?

Width of the stain

What are the goals of BPA examination?

to determine the area of origin/convergence, movement of a suspect/victim throughout the scene, possible mechanisms, estimation of PMI, and most importantly confirm or contradict suspect statements

What is Edward Potroscki known for?

devised the relationship between blunt force impact and spatter stains; “the bunny beater”

What is Herbert McDonald known for?

established the first BPA training course

Three main categories of blood stains

passive, spatter, and altered

Passive blood stains

anything that can be affected by gravity: transfer, drop, flow, large volume

Spatter blood stains

impact, secondary, projection (arterial or castoff stains)

Altered blood stains

clotted, diluted, diffused, insects, sequenced, voids

Area of Origin

where blood came from out in space (3D)

Area of Convergence

gives us the height above the surface of the blood source (2D)

Perforation

completely passing through an object

Penetration

going into an object; getting stuck

What is the firearms terminology for full ammunition

a cartridge

What do you include when documenting a firearm?

serial number, make & model, investigator manipulations, condition of the firearm

What is the definition of ballistics?

the science of the travel of a projectile in flight

Different types of ballistics

Internal, external, and terminal

Internal Ballistics

projectile traveling down the barrel of a gun when fired (within the gun itself)

External ballistics

the path of the projectile traveling in the air

Terminal ballistics

the projectile contacting a target and path into/through that target

How would you describe this if you found it at a scene?

It is what appears to be a fired bullet, deformed from an impact and it has striations which are visible to the naked eye.

How would you describe this if you found it at a scene?

Appears to be a spent silver casing whose head stamp information is Win 9mm Luger

T/F: diagrams are important for shooting reconstruction

True

Elevation Sketch

A sketch which depicts height/position measurements on a wall; Helpful for shooting reconstruction

Cross Projection or Exploded Sketch

A sketch which depicts position of doors/windows of all walls in a scene; Helpful for blood spatter exams

Why do we worry about terminology?

Allows for a better communication of ideas, avoids confusion, consistent reporting, and professionalism

Terminology used to describe a recovered bullet

Intact, fragment, deformed, or embedded

Target

object or surface struck by a bullet

Frangible

a surface subject to crumbling or breaking upon application of force (ex: concrete)

Non-frangible

surface that tends to bend or stretch upon application of force (ex: sheet metal)

Terminus

final resting place of a bullet

Flight path

path of the bullet

Angle of impact

interior angle where a bullet strikes a surface

Key hole defect

damage indicates the bullet started tumbling in air (hit something which changed its velocity & direction)

Ricochet

change in the angle/direction of the bullet

Boat waves

often seen in sheet metal, shows directionality of bullet in paint

Bullets striking a surface close to ninety degrees will produce _________ holes but those less than ninety degrees produce ________ shaped holes

round; irregularly

Shoulder

the location where the bullet first enters a target; illustrates direction of flight of the bullet

Exit holes in glass are generally _________ and create ________ on the crater

larger; beveling

Tempered Glass

safety glass that shatters on impact (passenger windows)

Laminated Glass

glass that stays together on impact, usually a layer of plastic, glass, then plastic (windshields)

What do contact entry wounds look like?

muzzle imprints, powder burns, stippling, and stellate (skin tearing)

Stippling

unburned powder grains exiting from the barrel causing pinpoint abrasions on the skin

Tools used for trajectory analysis

trajectory rods, protractor, and level

All measurements for placement of a bullet hole are taken from the ______ of the hole

center

Azimuth angle

side to side angle at which the bullet penetrated the surface, taken using a protractor

Vertical Angle

up and down angle at which the bullet penetrated a surface, taken using a level

Submillimeter blood means _____________.

Close proximity

What is this an example of:

“When stains are located low to the ground with upward directionality, the source of the blood had to be below that measurement”

Limiting Angles of Blood Spatter Stains

Flow patterns often assist CS investigators in determining if a body has been __________ or _______________.

moved or altered

Leuco-crystal violet is used to enhance blood that is ____________.

already visible

Bluestar & Luminol are used to reveal blood stains that were ______________.

previously unseen

A gunshot wound will result in _____ and ________ spatter

back and forwardblood and tissue

Spatter associated with gunshots

fine mist of droplets