Bloodstain Pattern Analysis (BPA) Quiz Prep

What is the purpose of Bloodstain Pattern Analysis (BPA)?

To analyze the physical nature of blood stains and to gain specific information about the events that occurred during an incident.

What information can BPA provide about a blood droplet?

The direction of travel, angle of impact, approximate distance from the target, nature of the force involved, approximate number of blows, relative positions of individuals

What is Crime Scene Reconstruction?

A method used to support a likely sequence of events at a scene by observing and evaluating physical evidence.

What should be considered when discovering bloodstains at a crime scene?

No specific protocol; use search techniques and recognize that bloodstains may contain other evidence like trace evidence, semen/saliva mixtures, and patterns.

What is the average blood volume in an adult person?

4.5 to 5.5 liters, with males having 5 to 6 liters and females 4 to 5 liters.

What is blood classified as in terms of fluid dynamics?

A non-Newtonian fluid that obeys the Laws of Motion.

What is surface tension and why is it important for BPA?

The property that gives blood droplets their shape and is the most important parameter for BPA.

What shape do blood droplets form and why?

A sphere to minimize surface area and energy.

What is the standard drop size of blood?

0.5 mL (500 µL).

How does the angle of impact affect blood stains?

The blood stain gets longer as the angle decreases.

What is directionality in bloodstains?

The characteristic indicating the direction the blood was moving at the time of deposition, with the tail pointing in the direction of travel.

What is the area of convergence in bloodstain analysis?

The approximate area where lines drawn through the length of chosen blood stains intersect.

What happens to blood when it drips from a surface?

It trickles down in a teardrop shape, which then settles into a sphere upon impact.

How does surface texture affect bloodstains?

Irregular surfaces can break the surface tension of spreading edges, resulting in satellite stains.

What factors influence the size of a blood stain?

Drop volume, distance it falls, and the surface it lands on.

What is the role of shear rate in blood behavior?

As the shear rate increases, the viscosity of blood decreases.

What is the significance of momentum in bloodstain analysis?

Momentum, defined as mass times velocity, is a key parameter in understanding the dynamics of blood droplets.

What is the relationship between blood droplet size and bleeding?

Rapid bleeding produces slightly larger drops, while movement results in smaller drops.

What is the effect of surface type on blood stain shape?

The shape of the stain depends on whether the surface is porous (like carpet) or non-porous (like glass).

What is the point of origin in bloodstain pattern analysis?

The 3D location from which bloodstains originated.

How is the angle of impact calculated in BPA?

Using the formula arcsin (width / length).

What is a bloodstain?

A deposit of blood on a surface.

What is a bloodstain pattern?

A grouping or distribution of bloodstains indicating how the bloodstain was deposited.

What are the types of passive bleeding patterns?

Drip stain, drip pattern, drip trail, accompanying drop, splash pattern.

What factors influence the size of a drip stain?

Volume of drop, height of fall, and the substrate the drop lands on.

What is a drip stain?

A blood stain resulting from a falling drop formed due to gravity.

What is a drip pattern?

A bloodstain pattern resulting from liquid blood dropping into another liquid, at least one of which is blood.

What is a satellite stain?

A smaller bloodstain that originated during the formation of a parent stain.

What is a drip trail?

A bloodstain pattern resulting from the movement of a source of blood between two points.

What is a splash pattern?

A bloodstain pattern resulting from a volume of liquid blood falling on or spilling onto a surface.

What is a flow pattern in bloodstain analysis?

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

What is a pool in bloodstain analysis?

A blood stain resulting from an accumulation of liquid blood on a surface.

What is a saturation stain?

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

What is a transfer stain?

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

What is the significance of using specific terminology in bloodstain pattern analysis?

It ensures clear communication within the forensic community and aids in educating the jury.

What is the role of the Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN)?

To provide accepted terminology and guidelines for bloodstain pattern analysis.

What characteristics define a drip pattern?

Large and irregular shape surrounded by small circular to elliptical satellite spatter.

What is an accompanying drop in bloodstain analysis?

A small blood drop produced as a byproduct of drop formation.

What determines the shape of a drip stain?

The angle at which it hits the surface and the surface characteristics.

What is the effect of surface texture on drip stains?

Smooth surfaces lead to more spread, while rough surfaces cause more breakup of the stain.

How does the height of a fall affect drip stains?

Higher falls result in larger stains, up to a certain height.

What is the significance of the serum stain?

It results from the liquid portion of blood that separates during coagulation.

What is a void in bloodstain pattern analysis?

An area where blood is absent due to an object blocking the blood's path.

What is the difference between active and passive bleeding sources?

Active sources produce continuous blood flow, while passive sources have limited blood release.

What are transfer stains?

Stains resulting from the transfer of blood from a blood-bearing surface onto another surface.

What are the characteristics of transfer stains?

Irregular shape, can range from very small to very large, may appear lighter in color, and may contain fingerprints, footprints, or fabric impressions.

What is a swipe pattern?

A bloodstain pattern resulting from the transfer of blood with relative motion between two surfaces.

What are the characteristics of a swipe pattern?

Irregular shape, can range from very small to very large, may indicate direction of movement, and may contain feathering demarcation, striations, or diminishing volume.

What is a wipe pattern?

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

What are the characteristics of a wipe pattern?

Alters the appearance of the original bloodstain, may show the outline of the original stain, and may indicate direction through feathering demarcation or diminished volume.

What is a smear in bloodstain analysis?

A stain or pattern created by the lateral transfer of blood through contact involving motion.

What are spatter stains?

Bloodstains resulting from a blood drop dispersed through the air due to an external force.

What factors affect the size and number of spatter stains?

The volume of blood and the amount of force applied.

What is an impact pattern?

A bloodstain pattern resulting from an object striking liquid blood.

What are the characteristics of impact spatter?

Consists of circular and elliptical stains, may radiate from a common point, and generally small in size.

What are expiration patterns in bloodstain analysis?

Bloodstain patterns resulting from blood forced by airflow out of the nose, mouth, or wound.

What should you look for in expiration patterns?

Mucous strands, bubble rings, or diluted areas.

What is the significance of bubble rings in bloodstains?

They indicate the presence of air in the blood, forming outlines within the bloodstain.

What are the characteristics of expirated patterns?

Expirated patterns consist of circular to elliptical stains, generally small (0.1 to 4 mm wide), and may contain air bubbles, mucous strands, or amylase from saliva.

What defines a projected bloodstain pattern?

A projected pattern results from the ejection of a volume of blood under pressure and can form many spines.

What are spines in bloodstain patterns?

Spines are pointed or elongated stains that radiate away from the central area of a bloodstain.

What are the characteristics of projected patterns?

Projected patterns can produce various shapes, often large in size, and may show flow from a large volume of blood. They can exhibit spines if the target is close to the source.

What is a cast-off pattern?

A cast-off pattern results from blood drops released from an object due to its motion, often in a linear or curvilinear orientation.

What factors influence the size and amount of stains in a cast-off pattern?

The size and amount of stains depend on the volume of blood, force of swing, and size of the source (e.g., bat vs knife).

What is a cessation cast-off pattern?

A cessation cast-off pattern results from blood drops released from an object due to its rapid deceleration, sharing characteristics with cast-off patterns.

What is a wave cast-off?

A wave cast-off is a small blood drop originating from a parent drop due to wave-like motion, pointing back to the parent stain.

What is a mist pattern?

A mist pattern results from blood reduced to a spray of microdrops due to a high degree of force, typically associated with gunshots.

What are the characteristics of a mist pattern?

Mist patterns consist of circular and elliptical stains, are very small (~0.01 to 1 mm wide), and may appear lighter in color.

What is a forward spatter pattern?

A forward spatter pattern arises from blood drops that travel in the same direction as the impact force, often from an exit wound.

What factors affect the amount of forward spatter?

The amount of forward spatter is influenced by caliber of firearm, muzzle to target distance, number of shots, wound characteristics, and blocking effects.

What is a back spatter pattern?

A back spatter pattern results from blood drops that travel in the opposite direction of the external force, associated with an entrance wound.

What conditions lead to back spatter patterns?

Back spatter generally occurs with close-range fire and is dependent on weapon type, ammunition, and wound site anatomy.

What is an altered stain?

An altered stain indicates a physical change has occurred, with swipes and wipes as examples.

What is a blood clot?

A blood clot is a gelatinous mass formed by red blood cells, fibrinogen, platelets, and other factors, often found in pools of blood.

What is a perimeter stain?

A perimeter stain consists of the peripheral characteristics of the original stain, indicating alteration.

What is a void in bloodstain patterns?

A void is an absence of blood in an otherwise continuous bloodstain pattern, indicating positioning or movement.

What are insect stains?

Insect stains result from insect activity, where flies ingest blood and regurgitate it, creating random, small stains (~1mm wide).