Bloodstain Pattern Analysis Quiz

Questions and Answers

Describe how to find the area of convergence.

The area of convergence is the point on a two-dimensional plane from which the drops in an impact pattern originated. This can be established by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails.

Describe how to find the area of origin.

The area of origin of an impact bloodstain pattern is the area in a three-dimensional space from which the blood was projected. This will show the position of the victim or suspect in space when the stain-producing event took place.

Which is 2D: the area of convergence or area of origin?

Area of Convergence (correct)

Area of Origin

Which is 3D: the area of convergence or area of origin?

Area of Origin Signup and view all the answers

You can calculate the angle at which a blood spatter impacts a surface.

True Signup and view all the answers

What formula do you use to find the angle of impact?

Sin A = Width of blood stain / Length of blood stain. Signup and view all the answers

When calculating the angle of impact, does the bigger number always go on the top or on the bottom of the equation?

False Signup and view all the answers

The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion.

True Signup and view all the answers

How do you discern the direction of travel of blood?

The pointed end of a bloodstain always faces its direction of travel. Signup and view all the answers

When blood is dropped at a right angle to a surface, what shape will it be?

At right angles, the blood drop is circular. Signup and view all the answers

How does the shape of a blood droplet/stain change as the angle decreases?

As the angle decreases, the stain becomes elongated. Signup and view all the answers

When does an impact spatter occur?

Impact spatter occurs when an object impacts a source of blood. Signup and view all the answers

What is impact spatter?

A bloodstain pattern produced when an object makes forceful contact with a source of blood, projecting drops of blood outward from the source. Signup and view all the answers

What is forward spatter? How does it occur?

Forward spatter is projected outward and away from the source. Signup and view all the answers

What is another name for back spatter?

Blow-back spatter. Signup and view all the answers

What information can be gathered from droplet size at a crime scene?

Using droplet size to classify impact patterns by velocity gives investigators insight into the general nature of a crime. Signup and view all the answers

What can not be found or deduced by impact patterns?

Droplet size cannot illuminate the specific events that produced the spatter pattern. Signup and view all the answers

Describe a low velocity spatter: size and distance of travel.

Drops with diameters of 4 mm or more, normally produced by an applied force of up to 5 ft/sec. Signup and view all the answers

Describe a medium velocity spatter: size and distance of travel.

Drops with diameters from 1-4 mm with an applied force of 5 to 25 ft/sec. Signup and view all the answers

Describe a high velocity spatter: size and distance of travel.

Drops with diameters of less than 1 mm from an applied force of 100 ft/sec or faster. Signup and view all the answers

What are the limitations of impact spatter and how should they be used?

The classifications of impact spatter as low, medium, and high velocity cannot illuminate the specific events that produced the stain size pattern. Signup and view all the answers

What causes impact spatter?

Occurs when an object impacts a source of blood. Signup and view all the answers

What action(s) causes impact spatter?

Blunt force trauma Signup and view all the answers

When does cast-off spatter occur?

Cast-off spatter occurs when a blood-covered object flings blood in an arc onto a nearby surface. Signup and view all the answers

What action causes arterial spurt pattern?

A main artery or the heart is punctured, resulting in large 'spurted' patterns with each heartbeat. Signup and view all the answers

Give example(s) of what creates high impact spatter.

Gunshot. Signup and view all the answers

Give examples of what creates medium impact spatter.

Baseball bat. Signup and view all the answers

Give examples of what creates low impact spatter.

Gravity. Signup and view all the answers

Which type of spatter (low, medium or high velocity) will travel the furthest from the source of blood?

Low velocity droplets have the highest mass and will travel the furthest from the source of blood. Signup and view all the answers

Describe the differences between impact, forward and back spatters.

Impact spatter occurs when an object impacts a source of blood. Forward spatter is projected outward and away from the source, while back spatter is projected backward from the source. Signup and view all the answers

What is drawback spatter?

Depending upon the distance from the victim that the gun was discharged, some back spatter may strike the gunman and enter the gun muzzle. Signup and view all the answers

What kind of spatter do you see with a gunshot? (3 types and 1 velocity)

High velocity spatter Signup and view all the answers

Which will cause larger cast-off spatter, a baseball bat or a knife?

Baseball bat Signup and view all the answers

Give examples of items that cause cast-off patterns.

Objects like a knife, a fist, or a baseball bat. Signup and view all the answers

Can you determine the exact number of blows that were made by looking at cast-off spatter patterns?

True Signup and view all the answers

Name the features that affect the cast-off patterns.

The size of the object, the amount of blood, and the direction the object was moving. Signup and view all the answers

What causes a cast-off spatter?

A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface. Signup and view all the answers

How does the color from an arterial blood spatter differ from other spatters?

The oxygenated blood spurting from the artery tends to be a brighter red color than blood expelled from impact wounds. Signup and view all the answers

How do you identify the site of the initial injury when an arterial blood spatter is present?

The site of the initial injury to the artery can be found where the pattern begins with the biggest spurt. Signup and view all the answers

What is arterial blood spatter?

Vertical arches showing fluctuations in blood pressure caused by an injury to the heart or a main artery. Signup and view all the answers

What is void spatter?

An area within a deposited spatter pattern that is clear of spatter, indicating that a person or object was blocking the void area. Signup and view all the answers

Void spatter is the most common type of bloodstain pattern found at a crime scene.

False Signup and view all the answers

What causes a void spatter?

A void is created when an object blocks the deposition of blood spatter onto a target surface. Signup and view all the answers

What can a void spatter tell a crime scene investigator?

The blank space may give a clue as to the size and shape of the missing object or person. Signup and view all the answers

What is an expirated blood pattern? Where does it come from?

An expirated blood pattern is created by blood that is expelled from the mouth or nose from an internal injury, and it appears bright due to air in bubbles. Signup and view all the answers

What is the significance of expirated blood pattern at a crime scene?

The presence of expirated blood gives an important clue as to the injuries suffered and the events that took place. Signup and view all the answers

Where does expirated blood come from?

Blood from the nose or mouth, and it is bright due to air in bubbles. Signup and view all the answers

How is expirated blood different in color from other spatters?

The presence of bubbles of oxygen in the drying drops or a lighter color as a result of dilution by saliva. Signup and view all the answers

What is skeletonization and how does it occur?

Skeletonization occurs when the edges of a stain dry to the surface, usually within 50 seconds of deposition. Signup and view all the answers

What does the skeletonization time indicate to an investigator?

Knowing the skeletonization time helps an investigator determine the timing of movement or activity. Signup and view all the answers

How long does it typically take for skeletonization to occur?

50 seconds for droplets and longer for larger volumes of blood. Signup and view all the answers

What is a contact/transfer pattern?

A contact or transfer pattern is created when an object with blood on it touches one that does not. Signup and view all the answers

Is a swipe pattern a type of transfer pattern?

Yes, a swipe pattern occurs when a bloody object moves across a surface. Signup and view all the answers

What is a flow pattern?

A flow pattern is a change in the shape and direction of a bloodstain due to the influence of gravity or movement of the object. Signup and view all the answers

What can flow patterns show?

The flow direction may show movements of objects or bodies while the flow was still in progress or after the blood dried. Signup and view all the answers

What can interruption of flow pattern tell a crime scene investigator?

Interruption of a flow pattern may indicate the sequence and passage of time between the flow and its interruption. Signup and view all the answers

What is a pool pattern?

A pool pattern is an undisturbed collection of blood on a level surface. Signup and view all the answers

What happens to the size of a pool pattern when it's on an absorbent surface?

Blood that pools on an absorbent surface may be absorbed and diffuse, creating a pattern larger than the original pool. Signup and view all the answers

What can the drying time of a blood pool tell a crime scene investigator?

The drying time can yield information about the timing of events that accompanied the incident. Signup and view all the answers

What is the difference between a drip pattern and drip trail?

A drip pattern is drop on drop, while a drip trail is a pattern of bloodstains formed by dripping off a moving surface. Signup and view all the answers

What is a drip trail pattern?

A drop trail pattern is a series of drops that are separate from other patterns, formed by blood dripping off an object or injury. Signup and view all the answers

What can a drip or drop trail pattern tell a crime scene investigator?

The pattern may show direction and speed of movement. Signup and view all the answers

What is a blood swipe?

Blood already on hand. Signup and view all the answers

What is blood wipe?

An altered bloodstain pattern resulting from an object moving through a preexisting wet bloodstain. Signup and view all the answers

What are blood swipe patterns?

A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface. Signup and view all the answers

How does the diameter of a blood drop pulled down only by gravity change as height changes?

Blood stain diameter increases as height increases. Signup and view all the answers

How can you tell the direction a blood drop was traveling?

The direction of travel of blood striking an object may be discerned because the pointed end of a bloodstain always faces its direction of travel. Signup and view all the answers

True or False: Blood that falls on glass will have less splatter than blood that falls on a soft surface.

True Signup and view all the answers

Study Notes

Bloodstain Pattern Analysis

The area of convergence determines where blood droplets originated by intersecting their tails in a 2D plane.
The area of origin provides a 3D perspective on where blood was projected, helping establish positions during an incident.
The angle of impact can be calculated using the formula: Sin A = Width of blood stain / Length of blood stain, where the larger number is the denominator.
Blood stains at a right angle are circular, while elongated stains indicate a shallower angle of impact.
Impact spatter is produced when an object strikes a blood source, resulting in outward projection of blood droplets.

Types of Spatter

Forward spatter ejects blood away from the source, while back spatter (or blow-back spatter) moves towards the source.
Cast-off spatter occurs when a blood-covered object flings blood in an arc after striking something.
Arterial spurt patterns arise from a punctured artery, producing large spurts with each heartbeat.

Spatter Velocity Classification

Low velocity spatter (4 mm diameter or larger) results from impacts under 5 ft/sec.
Medium velocity spatter (1-4 mm diameter) occurs from impacts between 5 to 25 ft/sec.
High velocity spatter (less than 1 mm diameter) results from impacts over 100 ft/sec.

Cast-off Patterns

Sizes of cast-off spatter vary between blunt objects (larger drops) and sharp objects (smaller drops).
The number of blows can be inferred from the count and arrangement of spatter patterns.
Factors influencing cast-off patterns include object size, blood amount, and movement direction.

Distinctive Blood Patterns

Void patterns indicate an absence of blood where an object or person obstructed blood deposition.
Expirated blood patterns come from blood expelled from injuries to the mouth or nose, often appearing bright due to bubbles.
Flow patterns depict blood movement influenced by gravity, deducing the position or movement of individuals involved.

Drip Patterns

Drip patterns consist of blood falling drop-by-drop, while drip trails show movement over time, potentially indicating direction and suspect identity.
Skeletonization occurs when blood edges dry within approximately 50 seconds, preserving an outline of the original stain.

Surface Interaction

Blood stains differ based on the surface; harder surfaces produce less spatter, while softer surfaces may exhibit more dispersion.
Stain size increases with height due to gravitational effects, affecting blood diameter upon impact.

Key Observations

The pointed end of a blood stain indicates its direction of travel.
Understanding the color variation in arterial blood spatter provides clues about the type of injury sustained.
Blood wipes occur when a moving object alters a bloodstain, indicating interaction with the existing pattern.

These bullet points encapsulate crucial information from the material on bloodstain pattern analysis, allowing for efficient study and review.

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Description

Test your knowledge of bloodstain pattern analysis, focusing on concepts like area of convergence, area of origin, and different types of spatter. This quiz will challenge your understanding of how to interpret blood evidence at a crime scene.