Crime Scene Investigation Final

Bloodstain Pattern Analysis

Analysis of the location, shape, size, and distribution of bloodstains.

Purpose of Bloodstain Pattern Analysis

To recreate the actions that caused the bloodshed.

Encountering Blood Evidence

Blood evidence can be found on the victim, at the crime scene, on a weapon, and on the assailant.

Target Surface

A surface onto which blood has been deposited.

Composition of Blood

Blood is composed of 55% plasma, less than 1% white blood cells and platelets, and 45% red blood cells.

SWGSTAIN

Scientific Working Group on Bloodstain Pattern Analysis.

Information Revealed by BPA

BPA reveals the origin, distance, direction, type of impact, number of blows, position, movement during and after bloodshed, and corroborates witness statements.

Surface Tension in Blood

Cohesive forces that minimize surface area by pulling surface molecules towards the interior of the liquid.

Shape of Blood Drops

Blood drops form spheres.

Free-Falling Blood Drop on Smooth Surface

Results in a circular bloodstain.

Effect of Increased Falling Distance

Increases the diameter of the resulting bloodstain.

Terminal Velocity

The maximum speed that a free-falling drop of blood can achieve in the air.

Volume and Terminal Velocity

Larger volumes of blood have higher terminal velocities.

Blood Drop on Textured Surface

The surface tension will rupture, distorting the shape and creating spines along the edges.

Satellite Stains

Smaller bloodstains originating from the parent stain during impact.

Angle for Circular Bloodstain

Blood must fall at 90 degrees to create a circular bloodstain.

Effect of Angle Less Than 90 Degrees

Creates an elliptical bloodstain.

Greater the Angle, the ___

Greater the elongation of the stain.

Directionality in Bloodstains

The tail of the stain points in the direction of travel.

Measuring Length of Bloodstain

Only the body of the stain is measured, not the tail.

Angle of Impact Equation

arc sin (width/length) in mm; answer in degrees.

Types of Bloodstains

Passive, transfer, and projected/impact.

Types of Passive Bloodstains

Drip stain, drip pattern, and pool.

Drip Stain

A bloodstain resulting from a falling drop due to gravity.

Drip Pattern

A bloodstain pattern from blood dripping into blood.

Pool

A bloodstain resulting from accumulated liquid blood on a surface.

Projected Bloodstains

Results from the ejection of blood under pressure or force.

Types of Projected Bloodstains

Impact pattern, cast-off pattern, expiration pattern, and arterial gushing/spurting.

Impact Pattern

Resulting from an object striking blood.

Cast Off Pattern

From blood drops released from an object due to its motion.

Expiration Pattern

Blood forced by airflow out of the nose, mouth, or a wound.

Arterial Gushing Pattern

Blood exiting the body under pressure from a breached artery.

Types of Transfer Bloodstains

Transfer/contact, swipe, and wipe.

Transfer/Contact Stain

From contact between a blood-bearing surface and another surface without motion.

Swipe Stain

Transfer of blood onto an unstained surface with motion.

Wipe Stain

An altered bloodstain from an object moving through a preexisting stain.

Voids in Bloodstains

An absence of blood in an otherwise continuous bloodstain.

Stringing Method

Conducted after documentation and before blood evidence collection.

Area of Convergence

The area indicating the location of the blood source in two dimensions.

Area of Origin

3D location from which spatter originated.

Accurate Bullet Trajectory Reconstruction

Requires two bullet defects (holes or impact sites).

Purpose of Trajectory Determination

To determine the bullet path and shooter’s position.

Zone 1 of Possibility

Area at or below the shooter's shoulder height in a comfortable position.

Zone 2 of Possibility

Possible locations for an awkward shooter stance.

Zone 3 of Possibility

Areas where the shooter could not have stood and fired.

Angle of Impact and Bullet Holes

Can elongate holes and may cause tumbling.

Entry Defect Characteristics

Regular margins are observed.

Exit Defect Characteristics

Irregular margins with crater formations indicating travel direction.

Trajectory Kits Components

Include trajectory rods, protractors, spacers, strings or lasers, and photographic fog.

Strings vs Lasers Accuracy

Laser trajectory is more accurate over long distances.

Measuring Entrance Hole

Vertical and horizontal distances from the floor and wall.

Measuring Exit Hole

Vertical distance and horizontal distance from the same wall as the entrance hole.

Angle of Impact Calculation

arcsin (width/length) in mm; answer in degrees.

FARO Focus 3D Scanner

Uses calibrated trajectory spheres to determine bullet path.

Victim Wound Bullet Trajectory

May help determine the position of the victim.

Wall Scope Function

Used to recover bullets behind walls with minimal damage.

Forensic Pathology

Study of sudden, unexpected, suspicious, or unnatural deaths.

Important Factors of a Death Investigation

Includes notification of the coroner, documentation, autopsy, post mortem interval, and identification.

Forensic Anthropology Role

Identifies human skeletal remains and estimates post mortem interval.

Forensic Odontology Purpose

Identifies deceased through age, trauma, and bite mark analysis.

Facial Reconstruction Methods

Includes drawing, clay reconstruction, and computer-aided reconstruction.

Taphonomy Definition

Postmortem history of the body.

Taphonomy Elements

Decomposition stages, trauma interpretation, scavenger modifications, insect activity, and environmental factors.

Types of Burial Indicators

Disturbed vegetation, soil compaction, and new vegetation.

Factors Affecting Burial Indicators

Time since burial, ground moisture, and terrain.

Tools for Searching Human Remains

Includes aerial photography, metal detectors, and cadaver dogs.

Search Area Definition

Large area searched when remains location is unknown.

Recovery Area Definition

Area containing the burial or surface remains.

Sequence of Excavation

Involves searching, staking, systematically removing layers, documenting, and collecting samples.

Sifting Stations Purpose

Ensures nothing is missed during troweling.

Scattered Remains Recovery Method

Detailed line search on hands and knees with buckets.

Forensic Entomology

Study of insects and related arthropods in legal issues.

Scope of Forensic Entomology

Involves death, abuse, and neglect investigations.

Uses of Forensic Entomology

Determine conditions at death, movement of body, location of injuries, drugs, and recovery of DNA.

Life Cycle of Blowfly Stages

Eggs hatch, larvae grow, prepupation, adult emergence.

Insect Succession During Decomposition

Sequential presence of different insects through decay stages.

Entomological Evidence Collection Steps

Include scene observations, weather data, and specimen collections.

Scene/Body Observations Details

Includes habitat type, GPS location, body position, and trauma notes.

Insect Activity Observations

Notes on species present and infestation locations.

Weather Data Records

Includes temperature, humidity, and official records from National Weather Service.