Bloodstain pattern analysis

Bloodstain Pattern Analysis (BPA)

The study of bloodstains at a crime scene to reconstruct the events that caused the bloodshed

Basic Components of Blood

Blood consists of liquid (plasma and serum) and solids (red and white blood cells

Blood Behavior After Leaving the Body

Blood exits the body as a liquid but begins to clot within minutes

Clotted Blood in Stains

Indicates a prolonged attack or that the victim bled for some time after injury

Three Basic Types of Bloodstains

Passive stains

Passive Stains

Bloodstains resulting from gravity acting on an injured body

Transfer Stains

Created when a bloodied object contacts another surface

Projected/Impact Stains

Result from blood being projected through the air

Gunshot Spatter

Bloodstain patterns from gunshots

Cast-Off Spatter

Blood flung from a moving object

Arterial Spray

Blood spurted from a severed artery

Expirated Spatter

Blood expelled from the mouth

Latent Bloodstains

Bloodstains not visible to the naked eye

Luminol Detection

Luminol reacts with iron in hemoglobin

Sharp Force Injury Patterns

Typically result in smaller

Blunt Force Injury Patterns

Produce larger

Importance of BPA

Helps reconstruct crime scenes

Factors Affecting Spatter

Speed of blood exit and type of force applied influence the characteristics of bloodstains

Bloodstain Directionality

Indicates the direction from which blood originated

Counting Blows in an Attack

Analysts can estimate the minimum number of blows by counting arcs in cast-off patterns

Pattern Analysis

Examination of the physical characteristics of bloodstain patterns

Reconstruction

Utilizing data from pattern analysis to provide contextual explanations for the bloodstain patterns

Area of Convergence

The point on a two-dimensional plane where lines traced through the long axes of bloodstains meet

Area of Origin

The three-dimensional location from which blood spatter originated

Surface Tension in Blood

The cohesive force at the surface of a blood droplet that causes it to maintain a spherical shape when falling

Effect of Surface Texture on Bloodstains* The texture of the surface upon which blood lands affects the shape and distribution of the resulting stains; smooth surfaces yield more uniform stains

while rough surfaces can cause irregularities

Volume of Blood and Pattern Clarity

The amount of blood present influences the clarity of patterns; excessive blood can obscure patterns

Overlapping Stains

Occur when multiple bloodstains are deposited in the same area

DNA Profiling from Bloodstains

The process of analyzing blood samples to identify individual DNA profiles

Collection of Bloodstain Evidence

Involves photographing stains with scales for reference

Documentation of Bloodstain Evidence

The systematic recording of bloodstain patterns through high-resolution photography

Role of Bloodstain Pattern Analysts

Professionals trained to examine and interpret bloodstain patterns

Angle of Impact

The angle at which a blood drop strikes a surface

Area of Convergence

The area containing the intersections generated by lines drawn through the long axes of individual stains

Area of Origin

The three-dimensional location from which blood spatter originated

Backspatter Pattern

A bloodstain pattern resulting from blood drops that traveled in the opposite direction of the external force applied; associated with an entrance wound created by a projectile

Blood Clot

A gelatinous mass formed by a complex mechanism involving red blood cells

Bloodstain

A deposit of blood on a surface

Bloodstain Pattern

A grouping or distribution of bloodstains that indicates through regular or repetitive form

Bubble Ring

An outline within a bloodstain resulting from air in the blood

Cast-off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its motion

Cessation Cast-off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its rapid deceleration

Drip Pattern

A bloodstain pattern resulting from a liquid that dripped into another liquid

Drip Stain

A bloodstain resulting from a falling drop that formed due to gravity

Drip Trail

A bloodstain pattern resulting from the movement of a source of drip stains between two points

Edge Characteristic

A physical feature of the periphery of a bloodstain

Expiration Pattern

A bloodstain pattern resulting from blood forced by airflow out of the nose

Flow Pattern

A bloodstain pattern resulting from the movement of a volume of blood on a surface due to gravity or movement of the target

Forward Spatter Pattern

A bloodstain pattern resulting from blood drops that traveled in the same direction as the impact force

Impact Pattern

A bloodstain pattern resulting from an object striking liquid blood

Luminol

A chemical that exhibits chemiluminescence

Mist Pattern

A bloodstain pattern resulting from blood reduced to a spray of micro-drops as a result of the force applied

Parent Stain

A bloodstain from which a satellite stain originated

Perimeter Stain

An altered stain that consists of the peripheral characteristics of the original stain

Plasma

The clear

Platelet

An irregularly shaped cell-like particle in the blood that plays a crucial role in blood clotting

Pool

A bloodstain resulting from an accumulation of liquid blood on a surface

Projected Pattern

A bloodstain pattern resulting from the ejection of a volume of blood under pressure

Satellite Stain

A smaller bloodstain that originated during the formation of the parent stain as a result of blood impacting a surface

Saturation Stain

A bloodstain resulting from the accumulation of liquid blood in an absorbent material

Serum Stain

The stain resulting from the liquid portion of blood (serum) that separates during coagulation

Spatter Stain

A bloodstain resulting from a blood drop dispersed through the air due to an external force applied to a source of liquid blood

Spines

Features resembling spokes or rays emanating out from the edge of a blood drop; result from the drop contacting a non-smooth surface

Splash Pattern

A bloodstain pattern resulting from a volume of liquid blood that falls or spills onto a surface

Swipe Pattern

A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface

Transfer Stain

A bloodstain resulting from contact between a blood-bearing surface and another surface

Void

An absence of blood in an otherwise continuous bloodstain or bloodstain pattern

Wipe Pattern

An altered bloodstain pattern resulting from an object moving through a preexisting wet bloodstain