Lecture 9: Bloodstain Pattern Analysis

Blood

Specialized body fluid that has four main components: plasma, red blood cells, white blood cells, and platelets

• Functions of blood

• Transporting oxygen and nutrients to the lungs and tissues

• Forming blood clots to prevent excess tissues

• Carrying cells and antibodies that fight infection

• Bringing waste products to the kidneys and liver which filter and clean the blood

• Regulate body temperature

Plasma

Liquid component of blood

A mixture of water, sugar, fat, protein, and salts

Function of plasma

To transport blood cells throughout your body along with nutrients, waste products, antibodies, clotting proteins, chemical messengers such as hormones, and proteins that help maintain the body’s fluid balance

Serum

Portion of plasma remaining after coagulation of blood, during which process the plasma protein fibrinogen is converted to fibrin and remains behind in the clot

• Red Blood Cells (RBC)

• Erythrocytes

• Most abundant cell in the blood

• Accounting for about 40-45% of its volume

• Contain hemoglobin which helps carry oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled

• Shape is a biconcave disk with a flattened center, they have no nucleus and can easily change shape, helping them fit through the various blood vessels in your body

• Survives for about 120 days

White Blood Cells (WBC)

• Leukocytes

• Protect the body from infection

• Account for 1% of blood

• Platelets

• Thrombocytes

• Help the blood clotting process (coagulation) by gathering at the site of an injury, sticking to the lining of the injured blood vessel, and forming a platform on which blood coagulation can occur

Blood clot

Gelatinous mass formed by a complex mechanism involving red blood cells, fibrinogen, platelets, and other clotting factors

Is blood commonly found at crime scenes?

Yes

What information can be obtained from bloodstain pattern reconstruction?

• The direction from which blood originated

• The angle at which a blood droplet struck a surface

• The location or position of a victim at the time a bloody wound was inflicted

• The movement of a bleeding individual within the crime scene

• The minimum number of blows that struck a bleeding victim

• The approximate location of an individual delivering blows that produced a bloodstain pattern

• The information from a bloodstain pattern can be used to assist in….

• The reconstruction of the crime

• The evaluation of statements from witnesses or crime participants

Blood Splatter vs Blood Spatter

Splatter: to splash and scatter upon impact

Spatter: to scatter or dash in small particles or drops

Not blood splatter!!!!

Blood spatter basics: a drop of blood is created when…

The volume of blood drops increases to a point where gravitational attraction acting upon the drop overcomes the cohesive forces of the blood source

Spheroid shape is due to the effect of surface tension as it falls through the air

Blood spatter basics: the laws of physics

When blood leaves the body as a drop, as spatter, or gushing flow, its behavior conforms to the laws of physics

Have to understand the physical forces involved in blood shedding events

As a fluid, blood has physical properties similar to

Water

Blood spatter basics: blood drops hold together in free flight through the forces of _____ and ________

Cohesion and Surface Tension

Cohesion

The molecular force between particles within a body or substance that acts to unite them

The liquid likes to stick to itself

Surface Tension

The tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area

Allows the liquid to resist an external force

Therefore, blood does not fall as a teardrop but as a

Sphere

Blood spatter analysis is built upon the sciences of

Physics, math, anatomy, physiology, chemistry, biochemistry, fluid dynamics, and logic

Blood spatter analysis: definition

The scientific study of the static consequences resulting from dynamic blood shedding events

Blood spatter analysis: methodology

• Examine and document the features, location, shape, size, distribution, and appearance of bloodstains

• Determine the classification of the bloodstain patterns

• Obtain additional information from police, hospital, and lab reports

• Analysis of BSP to determine the area of convergence or origin, directionality, and if possible, sequence of events

• Peer review of conclusions in report

Blood Spatter Reconstruction: looking at two types of events

Passive blood events that are a result of injury and someone is bleeding

When force was applied to create a blood shedding event: could be blunt force (hammer) or high force (gunshot wound)

True or False: only on bloodstain pattern can be in one location

False; need to identify all of them

Bloodstain

A deposit of blood on a surface

Bloodstain Pattern

A grouping or distribution of bloodstains that indicate through regular or repetitive form, order, or arrangement the manner in which the pattern was deposited

Target

A surface onto which blood has been deposited

Parent stain

A blood stain from which satellite stain originated

Satellite stain

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

Directionality

The characteristic of a bloodstain that indicates the direction blood was moving at the time of the deposition

Directionality angle

The angle between the long axis of a spatter stain and a defined reference line on the target

Angle of impact

The acute angle relative to the place of a target at which a blood drop strikes a target

Area of convergence

The space in two dimensions to which the directionalities of spatter stains can be retraced to determine the location of the spatter-producing event

Area of origin

The space in three dimensions to which the trajectories of spatter can be utilized to determine the location of the spatter-producing event

Accompanying drop

A small blood drop produced as a by-product of a drop formation

Altered stains

A bloodstain with characteristics that indicate a physical change has occurred

Examples: dried flaming blood, diluted bloodstain

Perimeter stain

An altered stain consisting of its edge characteristics, the central area has been partially or entirely removed

Wipe pattern

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

Back spatter pattern

A bloodstain pattern resulting from blood drops that can be produced when a projectile creates an entrance wound

Forward spatter pattern

A bloodstain pattern resulting from blood drops that can be produced when a projectile creates an exit wound

Bubble ring

An outline within a bloodstain resulting from the air in the blood

Cast-off pattern

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

How do you determine the number of strikes using cast off patterns?

Count the arcs +1 will provide a minimum number of blows

Cessation cast-off pattern

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

Drip stain

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

Drip pattern

A bloodstain pattern resulting from a liquid that dripped into another liquid at least one of which was blood

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

Spines

Pointed or elongated stains radiating away from the central part of the stain

Expiration pattern

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound

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

Impact pattern

A bloodstain pattern resulting from an object striking liquid blood

Insect stain

A bloodstain resulting from insect activity

RBS mixed with fecal matter of insects

You will have this if insects are present

Mist pattern

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

Passive bloodstain

Occurs when blood drips from a wound or object and are characterized by the presence of drops, drips, cloths, and pools of blood

Pool

a blood stain pattern resulting from an accumulation of liquid blood on a surface

Projected pattern

A bloodstain pattern resulting from the ejection of blood under hydraulic pressure, typically from a breach in the circulatory system

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

Splash pattern

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

Transfer stain

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

2 patterns: transfer pattern and swipe pattern

Transfer pattern

a bloodstain pattern that is created when a wet, bloody, surface comes in contact with a second surface

Swipe pattern

A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another unstained surface, with characteristics that indicate relative motion between the two surfaces

Void

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

True or False: Bloodstain pattern analysis is researched based and supported by research

True

Recognition vs Reconstruction

Recognition: identifying and recognizing the types of stains and patterns present at a scene

Reconstruction: uses info from recognition to interpret the physical events that created the patterns

OSAC standard

Must be practicing 80% of the time to be considered an expert

For bloodstain pattern to be interpreted it must be…

Capable of being replicated in the reconstructive phase

And then validated by peer review

(Frye and Daubert)