Chapter 10 - Bloodstain Pattern Analysis

High Velocity spatter

is created by a force traveling at 100 feet per second or faster and producing droplets with diameters of less than 1 millimeter. Very fine droplets Gunshot exit wounds or explosions commonly produce this type of spatter However, because the droplets are very small, they may not travel far; they may fall to the floor or ground, where investigative personnel could overlook them.

10.2 Quick Review

An impact spatter pattern occurs when an object impacts a source of blood. This produces forward spatter projected forward from the source and back spatter projected backward from the source. Impact spatter patterns can be classified as low-velocity (>4 mm>4 mm drops), medium-velocity (1-4 mm drops), or high-velocity (<1 mm<1 mm drops) for descriptive purposes. These categories should not be used to make assumptions about what kind of force created the pattern. The area of convergence is the point on a two-dimensional plane from which the drops of an impact spatter pattern originated. This area can be estimated by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails. The area of origin of a bloodstain pattern is the area in three-dimensional space from which blood was projected, showing the position of the victim or suspect when the stain-producing event took place. The string method is commonly used at a crime scene to approximate the area of origin.

Foward Spatter pattern

Blood splatter that is projected outward, away from the source Blood that travels away from the source in the saame direction as the force that caused the spatter. projected outward and away from the source, such as an exit wound

Other Bloodstain Patterns

Not all bloodstains at a crime scene appear as spatter patterns. The circumstances of the crime often create other types of stains that can be useful to investigators.

Area of Convergence

is the point on a two-dimensional plane from which the drops originated. This can be established by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails. The intersection of these lines is the area of convergence, and the approximate point of origin will be on a line straight out from this area. An object hitting a source of blood numerous times will never produce exactly the same pattern each time. One can therefore determine the number of impacts by drawing the area of convergence for groups of stains from separate impacts.

An area-of-origin determination

may be calculated at the discretion of the bloodstain analyst when the circumstances of the case warrant such a determination. All measurements of stains and calculations of angle of impact and point of origin should be recorded in crime-scene notes. Especially important stains can be roughly sketched within the notes.

It is possible to determine the impact angle of blood on a flat surface by...

measuring the degree of circular distortion of the stain.

Investigators should

note, study, and photograph each pattern and drop. This must be done to accurately record the location of specific patterns and to distinguish the stains from which laboratory samples were taken. The photographs and sketches can also point out specific stains used in determining the direction of force, angle of impact, and area of origin.

n Figure 10-2, the bloodstain pattern was...

produced by several droplets of blood that were traveling from left to right before striking a flat, level surface. O-o O= main drop -o = direction of blood splatter

A more acceptable approach for classifying a blood stain pattern should encompass

should encompass observations of stain size, shape, location, and distribution.

Satellite splatter

small droplets of blood distributed around a drop or pool of blood as a result of the blood hitting the target surface "Blood splatter around parent stain, with blood droplets whose pointed ends face against the dircetion of travel."

Direction and Angle of Impact

the direction of travel of blood that struck an object by studying the stain's shape. As the stain becomes more elliptical in shape, its direction becomes more discernible because the pointed end of a bloodstain faces its direction of travel.

The distorted or disrupted edge of an elongated stain indicates...

the direction of travel of the blood drop.

What is useful for interpreting and reconstructing the events that accompanied the bleeding?

the location, distribution, and appearance of bloodstains and spatters A thorough analysis of the significance of the position and shape of blood patterns with respect to their origin and trajectory is exceedingly complex and requires the services of an examiner who is experienced in such determinations. the interpretation of bloodstain patterns necessitates a carefully planned control experiment using surface materials comparable to those found at the crime scene

Angle of Impact

The angle of the source of the blood to the surface where it was deposited. It caan be estimated from the width-to-length ratio of the stian to help determine the position of the victim or the weapon at thee time when the bleeding wound was inflicted.

Blood spatter patterns can arise from a number of distinctly different sources

that will be discussed in this chapter. Illustrations of patterns emanating from impact, cast-off, and arterial spray are shown in Figure 10-6. Impact: Blood splatteers on waall behind them, all around Cast off: When the soource picks up the weapon, blood comes off the weapon and splatters upwaards along the wall (going up the ceiling) Arterial Spray: Blood splattering from the victim.

Determining the Angle of Impact of Bloodstains

To determine the angle of impact, calculate the stain's length-to-width ratio and apply the formula Sin A = Width of blood stain DIVIDED by/ length of blood stain.

Medium Velocity spatter

is created by a force traveling at 5-25 feet per second and producing drops with diameters of between 1 and 4 millimeters. predominantly consisting of small drops normally associated with blunt-force trauma to an individual or with other applied forces moving at 5 to 25 feet per second.

Surface Texture

is of paramount importance in the interpretation of bloodstain patterns; comparisons between standards and unknowns are valid only when identical surfaces are used. In general, harder and nonporous surfaces (e.g., glass or smooth tile) result in less spatter. Rough surfaces, such as a concrete floor or wood, usually result in irregularly shaped stains with serrated edges, possibly with satellite spatter

A drop deposited at an angle of impact of about 90 degrees...

(directly vertical to the surface) will be approximately circular in shape with no tail or buildup of blood. However, as the angle of impact deviates from 90 degrees, the stain becomes elongated in shape. Buildup of blood will occur when the angles are larger, whereas longer and longer tails will appear as the angle of impact becomes smaller

What can a bloodstain pattern tell you?

- 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 at 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

Cast-Off Spatter

A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface. This kind of pattern commonly occurs when a person pulls a bloody fist or weapon back between delivering blows to a victim (see Figure 10-6[b]). The bloodstain tails will point in the direction that the object was moving. The width of the cast-off pattern created by a bloody object may help suggest the kind of object produced by the pattern. The sizes of the drops are directly related to the size of the point from which they were propelled. Drops propelled from a small or pointed surface will be smaller and the pattern more linear; drops propelled from a large or blunt surface will be larger and the pattern wide. The volume of blood deposited on an object from the source also affects the size and number of droplets in the cast-off pattern. The less blood on the object, the smaller the stains produced. The pattern may also suggest whether the blow that caused the pattern was directed from right to left or left to right. The pattern will point in the direction of the backward thrust, which will be opposite the direction of the blow. This could suggest which hand the assailant used to deliver the blows. Cast-off patterns may also show the minimum number of blows delivered to a victim. Each blow should be marked by an upward-and-downward or forward-and-backward arc pattern (see Figure 10-10). By counting and pairing the patterns, one can estimate the minimum number of blows. An investigator should take into consideration that the first blow would cause blood only to pool to the area; it would not produce a cast-off pattern. Also, some blows may not come into contact with blood and therefore will not produce a pattern. The medical examiner is in the best position to estimate the number of blows a victim received.

Drip Trail Patterns

A drip trail pattern is a series of drops that is separate from other patterns, and it is formed by blood dripping off an object or injury. The stains form a kind of line, usually the path made by the suspect after injuring or killing the victim. It may simply show movement, lead to a discarded weapon, or provide identification of the suspect if it is made from the suspect's own blood. Investigators often see this type of pattern in stabbings during which the criminal inadvertently cuts themself as a result of using the force necessary to stab the victim. Figure 10-18 shows a drip trail pattern away from the center of action at a crime scene. The shape of the stains in a drip trail pattern can help investigators determine the direction and speed at which a person was moving. The tails of the drops in a trail pattern point in the direction the person was moving. More circular stains are found where the person was moving slowly. This information may be helpful in reconstruction.

Expirated Blood Patterns

A pattern created by blood that is expelled from the mouth or nose from an internal injury is called an expirated blood pattern. If the blood that creates such a pattern is under great pressure, it produces very fine high-velocity spatter. Expirated blood at very low velocities produces a stain cluster with irregular edges. The presence of bubbles of oxygen in the drying drops can differentiate a pattern created by expirated blood from other types of bloodstains. Expirated blood also may be lighter in color than impact spatter as a result of being diluted by saliva. The presence of expirated blood gives an important clue to the injuries suffered and the events that took place at a crime scene.

Pools

A pool of blood occurs when blood collects in a level (not sloped) and undisturbed place. Blood that pools on an absorbent surface may be absorbed throughout the surface and diffuse, creating a pattern larger than the original pool. This often occurs to pools on beds or sofas. The approximate drying time of a pool of blood is related to the environmental condition of the scene. By experimentation, an analyst may be able to reasonably estimate the drying times of stains of different sizes. Small and large pools of blood can be helpful in reconstruction because they can be analyzed to estimate the amount of time that has elapsed since the blood was deposited. Considering the drying time of a blood pool can yield information about the timing of events that accompanied the incident. The edges of a stain will dry to the surface, producing a phenomenon called skeletonization (see Figure 10-17). This usually occurs within 50 seconds of deposition for droplets, and it takes longer for larger volumes of blood. If the central area of the pooled bloodstain is then altered by wiping, the skeletonized perimeter will be left intact. This can be used to interpret whether movement or activity occurred shortly after the pool was deposited or later, after the perimeter had time to skeletonize first. This may be important for classifying the source of the original stain.

Gunshot Spatter

A shooting may leave a distinct gunshot spatter pattern. This may be characterized by both forward spatter from an exit wound and back spatter from an entrance wound. The presence of backspatter on a firearm or a shooter is dependent on the distance between the firearm and victim. Forward spatter generally leaves a pattern of very fine droplets characteristic of high-velocity spatter. Medium- and large-sized drops may also be observed within the spatter pattern. The location of injury, the size of the wound created, and the distance between the victim and the muzzle of the weapon all affect the amount of back spatter that occurs. Finding high-velocity spatter containing the victim's blood on a suspect can help investigators place the suspect in the vicinity when the gun was discharged. Back spatter created by a gunshot impact generally contains fewer and smaller, atomized stains than does forward spatter. Muzzle blast striking an entrance wound will cause the formation of atomized blood. Depending on the distance from the victim that the gun was discharged, some back spatter may strike the gunman and enter the gun muzzle. This is called the "drawback effect." Blood within the muzzle of a gun can "place" the weapon in the vicinity of the gunshot wound. The presence of blow-back spatter on a weapon's muzzle is consistent with the weapon's having been close to the victim at the time of firing.

Void Patterns

A void is created when an object blocks the deposition of blood spatter onto a surface or object. The spatter is deposited onto the object or person instead. The blank space on the surface or object may give a clue to the size and shape of the missing object or person. Once the object or person is found, the missing piece of the pattern should fit in, much like a puzzle piece, with the rest of the pattern. Voids may help establish the body position of the victim or assailant at the time of the incident. A void pattern is found behind a door where the surface of the door blocked the deposition of spatter on that area. This void, and the presence of spatter on the door, shows that the door was open when the spatter was deposited.

Case Files - Bloodstain Reconstruction

An older male was found lying dead on his living room floor. He had been beaten about the face and head, stabbed in the chest, and robbed. The bloodstains found on the interior front door and the adjacent wall documented that the victim was beaten about the face with a fist and struck on the back of the head with his cane. A three-dimensional diagram and photograph illustrating the evidential bloodstain patterns are shown in Figures 1(a) and (b). A detail photograph of bloodstains next to the interior door is shown in Figure 2. Arrow 1 in Figure 2 points to the cast-off pattern directed left to right as blood was flung from the perpetrator's fist while inflicting blows. Arrow 2 in Figure 2 points to three transfer impression patterns directed left to right as the perpetrator's bloodstained hand contacted the wall, as the fist blows were being inflicted on the victim. Arrow 3 in Figure 2 points to blood flow from the victim's wounds as he slumped against the wall. Figure 3 contains a series of laboratory test patterns created to evaluate the patterns contained within Figure 2. Figure 4 shows how the origin of individual impact spatter patterns located on the wall and door and emanating from the bleeding victim can be documented by the determination of separate areas of convergence. A suspect was apprehended three days later, and he was found to have an acute fracture of the right hand. When he was confronted with the bloodstain evidence, the suspect admitted to striking the victim, first with his fist, then with a cane, and finally stabbing him with a kitchen knife. The suspect pleaded guilty to three first-degree felonies.

Arterial Spray Spatter

Arterial spray spatter is created when a victim suffers an injury to a main artery or the heart. The pressure of the continuing pumping of blood causes blood to spurt out of the injured area. Commonly, the pattern shows large spurted stains for each time the heart pumps. Some radial spikes, satellite spatter, or flow patterns may be evident because of the large volume of blood being expelled with each spurt. Drops may also be seen on the surface in fairly uniform size and shape and in parallel arrangement. The lineup of the stains shows the victim's movement. Any vertical arcs or waves in the line show fluctuations in blood pressure. The larger arterial stains are at the end of the overall pattern. The site of the initial injury to the artery can be found where the pattern begins with the biggest spurt. Arterial patterns can also be differentiated because the oxygenated blood spurting from the artery tends to be a brighter red color than blood expelled from impact wounds.

The Sam Sheppard Case: A Trail of Blood

Convicted in 1954 of bludgeoning his wife to death, Dr. Sam Sheppard achieved celebrity status when the storyline of TV's The Fugitive was apparently modeled on his efforts to seek vindication for the crime he professed not to have committed. Dr. Sheppard, a physician, claimed he was dozing on his living room couch when his pregnant wife, Marilyn, was attacked. Sheppard's story was that he quickly ran upstairs to stop the carnage but was knocked briefly unconscious by the intruder. The suspicion that fell on Dr. Sheppard was fueled by the revelation that he was having an adulterous affair. At trial, the local coroner testified that a pool of blood on Marilyn's pillow contained the impression of a "surgical instrument." After Sheppard had been imprisoned for ten years, the U.S. Supreme Court set aside his conviction because of the "massive, pervasive, and prejudicial publicity" that had attended his trial. In 1966, the second Sheppard trial commenced. This time, the same coroner was forced to back off from his insistence that the bloody outline of a surgical instrument was present on Marilyn's pillow. However, a medical technician from the coroner's office now testified that blood on Dr. Sheppard's watch was from blood spatter, indicating that Dr. Sheppard was wearing the watch in the presence of the battering of his wife. The defense countered with the expert testimony of eminent criminalist Dr. Paul Kirk. Dr. Kirk concluded that blood spatter marks in the bedroom showed the killer to be left-handed. Dr. Sheppard was right-handed. Dr. Kirk further testified that Sheppard stained his watch while attempting to obtain a pulse reading. After less than 12 hours of deliberation, the jury failed to convict Sheppard. But the ordeal had taken its toll. Four years later, Sheppard died, a victim of drug and alcohol use.

bloodstain patterns

Crime-scene analysts have come to appreciate that bloodstain patterns deposited on floors, walls, ceilings, bedding, and other relevant objects can provide valuable insights into events that occurred during the commission of a violent crime.

Terminology Bloodstain Patterns

DIP TRAIL PATTERN- A pattern of bloodstains formed by the dripping of blood off a moving surface or person in a recognizable pathway separate from other patterns SKELETONIZATION - The process by which the edges of a bloodstain dry to the surface in a specific period of time FLOW- A bloodstain pattern formed by the movement of small or large amounts of blood as a result of gravity's pull. TRANSFER PATTERN - A bloodstain pattern created when a surface that carries wet blood comes into contaact with a second surfaace VOID - An area within a deposited spatter pattern that is clear of spatter, caused by an object or person blocking the area at the time of the spatter's deposition.

10.2 Impact Bloodstain Spatter Patterns

Describe the classifications of impact spatter patterns and the methods of determining their area of convergence and area of origin.

10.4 Documenting Bloodstain Pattern Evidence

Describe the methods for documenting bloodstain patterns at a crime scene.

10.1 General Features of Bloodstain Formation

Discuss the information that can be gained from bloodstain pattern analysis about the events involved in a violent crime, specifically regarding surface texture, directionality, and angle of impact.

A common method for determining the area of origin at the crime scene is called the "string method."

Find the area of convergence for the stain pattern. Place a pole or stand as an axis coming from the area of convergence. Attach one end of a string next to each droplet. Place a protractor next to each droplet and lift the string until it lines up with the determined angle of impact of the drop. Keeping the string in line with the angle, attach the other end of the string to the axis pole. View the area of origin of the droplets where the strings appear to meet. Secure the strings at this area.

Glass (nonporous surface) vs rough surface

Glass- In the figure we can see when a drop of blood struck the glass (falling 24 inches) it was a perfect circle with no other splatter. (created less splatter) But when the single drop struct a cotton muslin sheet (falling 24 inches) there was other small splatter surrounding the "main drop" (satellite splatter) and it was not a perfect circle.

10.3 Quick Review

Gunshot spatter can consist of both forward spatter from an exit wound and back spatter from an entrance wound; however, only back spatter will be produced if the bullet does not exit the body. A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface. This kind of pattern commonly occurs when a person pulls a bloody fist or weapon back between delivering blows to a victim. The characteristic arterial spray spatter is created when a victim suffers an injury to a main artery or the heart, and the pressure of the continuing pumping of blood projects blood out of the injured area in spurts, which are apparent in the pattern. Expirated blood is expelled from the mouth or nose and may appear as very fine high-velocity spatter or large low-velocity bloodstain clusters. This kind of pattern may contain bubbles of oxygen or be mixed with saliva. A void pattern is an area free of spatter where an object (or person) blocked the deposition of blood spatter onto a surface or object. Because the spatter was deposited onto the object or person instead, the shape of the void may give a clue about the size and shape of the missing object or person.

VIDEO: The most common type of blood stain pattern found at a crime scene is...

Impact Splatter

Velocity and Force impact spatter

Impact spatter can be classified based upon velocity of the force impacting a blood object In general, as the velocity of the force of impact on the blood source increases, so does the velocity of the blood droplets emanating from the source. It is also generally true as both force and velocity of impact increase, the diameter of the resulting blood droplets decreases.

Origin of Impact Patterns

Impact spatter patterns can offer investigators clues about the origin of the blood spatter and, therefore, the position of the victim at the time of the impact.

Investigators have derived a common classification system of impact spatter based on the velocity of the force impacting on a bloody object.

In general, as the velocity of the force of the impact on the source of blood increases, so does the velocity of the blood droplets emanating from the source. It is also generally true that, as both the force and velocity of impact increase, the diameter of the resulting blood droplets decreases.

Quick Review 10.1

Individual bloodstains can convey to the bloodstain analyst the directionality and angle of impact of the blood when it impacted a surface. Bloodstain patterns may convey to the analyst the location of the victim (who was bleeding) or suspect (who was causing the bleeding), the movement of bleeding individuals, and the number of blows delivered. Surface texture is of paramount importance in the interpretation of bloodstain patterns; rounder drops generally are produced on smooth, nonporous surfaces, whereas rough surfaces result in irregular-edged drops. However, correlations between standards and unknowns are valid only when identical surfaces are used. The direction of travel of blood that struck an object may be discerned by the stain's shape. The pointed end of a bloodstain always faces its direction of travel. The angle of impact of an individual bloodstain can be approximated by the degree of distortion or lengthening of the bloodstain, or it can be more effectively estimated using the width-to-length ratio of the stain.

CHAPTER REVIEW

Individual bloodstains can convey to the bloodstain analyst the directionality and angle of impact of the blood when it impacted a surface. Bloodstain patterns may convey to the analyst the location of victims (who was bleeding) or suspects (who was causing the bleeding), the movement of bleeding individuals, and the number of blows delivered. Surface texture is of paramount importance in the interpretation of bloodstain patterns; rounder drops generally are produced on smooth, nonporous surfaces, whereas rough surfaces result in irregular-edged drops. However, correlations between standards and unknowns are valid only when identical surfaces are used. The direction of travel of blood that struck an object may be discerned by the stain's shape. The pointed end of a bloodstain always faces its direction of travel. The angle of impact of an individual bloodstain can be approximated by the degree of distortion or lengthening of the bloodstain, or it can be more effectively estimated using the width-to-length ratio of the stain. 10.2 An impact spatter pattern occurs when an object impacts a source of blood. This produces forward spatter projected forward from the source and back spatter projected backward from the source. Impact spatter patterns can be classified as low-velocity (>4 mm>4 mm drops), medium-velocity (1-4 mm drops), or high-velocity (<1 mm<1 mm drops) for descriptive purposes. These categories should not be used to assume what kind of force created the pattern. The area of convergence is the point on a two-dimensional plane from which the drops of an impact spatter pattern originated. This area can be estimated by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails. The area of origin of a bloodstain pattern is the area in three-dimensional space from which blood was projected, showing the position of the victim or suspect when the stain-producing event took place. The string method is commonly used at a crime scene to approximate the position of the area of origin. 10.3 Gunshot spatter can consist of both forward spatter from an exit wound and back spatter from an entrance wound; however, only back spatter will be produced if the bullet does not exit the body. A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface. This kind of pattern commonly occurs when a person pulls a bloody fist or weapon back between delivering blows to a victim. The characteristic arterial spray spatter is created when a victim suffers an injury to a main artery or the heart, and the pressure of the continuing pumping of blood projects blood out of the injured area in spurts, which are apparent in the pattern. Expirated blood is expelled from the mouth or nose and may appear as very fine high-velocity spatter or large low-velocity bloodstain clusters. This kind of pattern may contain bubbles of oxygen or be mixed with saliva. A void pattern features an area free of spatter where an object (or person) blocked the deposition of blood spatter onto a surface or object. Because the spatter was deposited onto the object or person instead, the shape of the void may give a clue about the size and shape of the missing object or person. Transfer patterns are created when an object with blood on it makes simple contact with a surface or moves along a surface. The direction of movement may be shown by a feathering of the pattern. Flows may originate from a single drop or a large amount of blood. Because the direction of the flow is caused by gravity, the direction of a pattern may suggest the original position of the surface when the flow was formed. A pool is formed where large amounts of blood collect. The pool may be absorbed into the surface of deposition over time. The presence of skeletonization on a feathered bloodstain suggests that the stain was disturbed after the perimeter had had sufficient time to dry. A drip trail pattern is separate from other patterns, and it is formed by a series of single blood droplets dripping off an object or injury. 10.4 Photographs and sketches should first be created of the overall bloodstain pattern to show the orientation of the pattern to the scene. Medium-range and close-up photographs may use the grid method or perimeter ruler method to show the orientation and relative size of the pattern and individual stains.

Back Spatter (Blow-Back Spatter) pattern

Is blood projected backward from a source, such as an entrance wound. Blood directed back toward the slurce of the force that caused the spatter. Potentially onto the person or object that created the impact.

Area of Origin

It may also be important to determine the area of origin of a bloodstain pattern, 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. The distribution of the droplets in an impact pattern gives a general idea of the distance from the blood source to the bloodstained surface. Impact patterns produced at a distance close to the surface will appear as clustered stains. As the distance from the surface increases, so do the distribution and distance between droplets.

Photographs of Blood Spatter

Just as in general crime-scene photography, the investigator should create photographs and sketches of the overall pattern to show the orientation of the pattern to the scene. The medium-range documentation should include pictures and sketches of the whole pattern and the relationships between individual stains within the pattern. The close-up photographs and sketches should show the dimensions of each individual stain. Close-up photographs should be taken with a scale of some kind showing in the photograph.

Flows

Patterns made by drops or large amounts of blood flowing with the pull of gravity are called flows. Flows may be formed by single drops or large volumes of blood coming from an actively bleeding wound or blood deposited on a surface, from an arterial spurt, for example. Clotting of the blood's solid parts may occur when a flow extends onto an absorbent surface. The flow direction may show movements of objects or bodies while the flow was still in progress or after the blood had dried. Figure 10-16 illustrates a situation in which movement of the surface while the flow was still in progress led to a specific pattern. Interruption of a flow pattern may be helpful in assessing the sequence and passage of time between the flow and its interruption. If a flow found on an object or body does not appear to be consistent with the direction of gravity, one may surmise that the object or body was moved after the blood had dried.

10.4 QUICK REVIEW

Photographs and sketches should first be created of the overall bloodstain pattern to show the orientation of the pattern to the scene. Medium-range and close-up photographs may use the grid method or perimeter ruler method to show the orientation and relative size of the pattern and individual stains.

Blood Spatter Terminology

Satellite Spatter - Blood Spatter around parent stain, with blood droplets whose pointed ends face against the direcction of travel Area of Coverage- The area on a two- dimensional plane where lines traced through the long axis of several bloodstains meet Area of Origin - The location in three- dimensional space from which blood that produced a bloodstain originated Cast off - A bloodstain pattern that is created when blood is flung from a blood-bearing object in motion onto a surface Arterial Spray - A characteristic bloodstain pattern caused by spurts that resulted from blood exiting under pressure from an arterial injury Expirated blood pattern - A pattern created by blood that is expelled out of the nose, mouth, or respiratory system as the result of air pressure and/or airflow

Case File: Blood Spatter Evidence

Stephen Scher banged on the door of a cabin in the woods outside Montrose, Pennsylvania. According to Scher, his friend, Marty Dillon, had just shot himself while chasing after a porcupine. The two had been skeet shooting at Scher's cabin, enjoying a friendly sporting weekend, when Dillon spotted a porcupine and took off out of sight. Scher heard a single shot and waited to hear his friend's voice. After a few moments, he chased after Dillon and found him lying on the ground near a tree stump, bleeding from a wound in his chest. Scher administered CPR after locating his dying friend, but he was unable to save Dillon, who later died from his injuries. Police found that Dillon's untied boot had been the cause of his shotgun wound. They determined he had tripped while running with his loaded gun and shot himself. The grief-stricken Scher aroused no suspicion, so the shooting was ruled an accident. Shortly thereafter, Scher moved away from Montrose, divorced his wife, and married Dillon's widow. This was too suspicious to be ignored; police reopened the case and decided to reconstruct the crime scene. The reconstruction provided investigators with several pieces of blood evidence that pointed to Scher as Dillon's murderer. Police noticed that Scher's boots bore the unmistakable spray of high-velocity impact blood spatter, evidence that he was standing within an arm's length of Dillon when Dillon was shot. This pattern of bloodstains would not be expected to be created while administering CPR, as Scher claimed had happened. The spatter pattern also clearly refuted Scher's claim that he did not witness the incident. In addition, the tree stump near Dillon's body bore the same type of blood spatter, in a pattern that indicated Dillon was seated on the stump, not running, when he was shot. Finally, Dillon's ears were free of the high-velocity blood spatter that covered his face, but blood was on his hearing protectors found nearby. This is a clear indication that he was wearing his hearing protectors when he was shot and they were removed before investigators arrived. This and other evidence resulted in Scher's conviction for the murder of his long-time friend, Marty Dillon.

Bloodstain Pattern Analysis: Proceed with Caution

The field of bloodstain pattern analysis has proliferated within the forensic science community, as well as with practitioners who pride themselves as being called crime scene investigators. Within the law enforcement community, there are hundreds of investigators (not necessarily scientists) who are proud to be labeled blood spatter specialists. At this point in time, there is no measurement to judge the uniformity of training in this field within the United States. The closest training criteria stems from the Bloodstain Pattern Analysis Cortication program offered under the auspices of the International Association of Bloodstain Pattern Analysis. The certificate requires a minimum of forty hours of education in an approved workshop. A minimum of three years of practice within the discipline of bloodstain pattern identification augments the classroom training. Under the best of circumstances, following the successful completion of the certificate requirements, many law enforcement agencies find it appropriate to insert these individuals into the crime-scene investigation process. The complexity of blood spatter interpretation runs the gamut from the simple to the complex. What should be worrisome to the forensic science community and the judicial system is the apparent absence of uniformity in imposing quality assurance standards on interpreting bloodstain patterns. The forensic science community is already reeling from adverse and embarrassing publicity arising from the misidentification of fingerprints, bullet lead, bite mark impressions, and hair evidence. Warnings are already being clearly and loudly sounded about the error rates associated with bloodstain pattern analysis. In a series of studies sponsored by the National Institute of Justice (NIJ), very high error rates for blunt instrument spatter patterns in the range of 37 percent have been reported. Where a bloodstain pattern classification was required, 13.1 percent of these classifications did not include the correct pattern for rigid surfaces and 23.4 percent for fabric surfaces.28 Another NIJ study has demonstrated that fabrics may interact to, distort, and alter a bloodstain pattern in many different and complex ways compared to bloodstains on hard surfaces. Given the highly subjective nature of bloodstain pattern interpretation and its potential significant error rate, a process of independent assessment of any bloodstain pattern interpretation by two or more examiners at the crime scene and in the laboratory is desirable. The "Analysis, Comparison and Evaluation-Verification" (ACE-V) process utilized by fingerprint examiners may serve as a useful model for general advisory guidance in bloodstain pattern evidence verification.

Two common methods of documenting bloodstain patterns place attention on the scale of the patterns.

The grid method involves setting up a grid of squares of known dimensions over the entire pattern using string and stakes (see Figure 10-19). All overall, medium-range, and close-up photographs are taken with and without the grid. The second method, called the perimeter ruler method, involves setting up a rectangular border of rulers around the pattern. In this method, the large rulers show scale in the overall and medium-range photos, whereas the small rulers can be inserted to show scale in the close-up photographs (see Figure 10-20). Some investigation teams use tags in close-up photographs to show evidence numbers or other details.

Example with angle blood splatter (figure 10)

The higher pattern is of a single drop of human blood that fell 24 inches and struck hard, smooth cardboard at 50 degrees. On this drop the collection of blood shows the direction. The lower pattern is of a single drop of human blood that fell 24 inches and struck hard, smooth cardboard at 15 degrees. On this drop the tail shows the direction.

1. Which of the following statements about documenting bloodstain pattern evidence is true?

The perimeter ruler method involves setting up a rectangular border of rulers around the pattern and then placing a small ruler next to each stain. Investigators should note, study, and photograph each pattern and drop of blood at a scene. The grid method of documenting bloodstain patterns sets up a grid of squares of known dimensions over the entire pattern using string and stakes. All of the above ALL OF THE ABOVE

Example of determing angle of blood stain

The width of a stain is 11 mm and the length is 22 mm. 11mm / 22mm = 0.50mm A scientific calculator that has the trigonometry function will calculate that the inverse sine of 0.50 is equal to a 30-degree angle. The measurements for length and width should be made with a ruler, micrometer, or photographic loupe.

Impact Spatter patterns

This type of pattern occurs when an object impacts a source of blood. Impact spatter patterns consist of many droplets radiating in direct lines from the origin of the blood to the stained surface.

10.3 PART 2 QUICK REVIEW

Transfer patterns are created when an object with blood on it makes simple contact with a surface or moves along a surface. The direction of movement may be shown by a feathering of the pattern. Flows may originate from a single drop or a large amount of blood. Because the direction of the flow is caused by gravity, the direction of a pattern may suggest the original position of the surface when the flow was formed. A pool is formed where large amounts of blood collect. The pool may be absorbed into the surface of deposition over time. The presence of skeletonization on a feathered bloodstain suggests that the stain was disturbed after the perimeter had had sufficient time to dry. A drip trail pattern is separate from other patterns, and it is formed by a series of single blood droplets dripping off an object or injury.

10.3 More Bloodstain Spatter Patterns

Understand how various blood pattern types are created and which features of each pattern can be used to aid in reconstructing events at a crime scene.

Contact/Transfer Patterns

When an object with blood on it touches another object that did not have blood on it, this produces a contact or transfer pattern. Examples of transfers with features include fingerprints, handprints, footprints, footwear prints, tool prints, and fabric prints in blood. These may provide further leads by offering individual characteristics. The size and general shape of a tool may be seen in a simple transfer. This can lead to narrowing the possible tools by class characteristics. A transfer that shows a very individualistic feature may help point to the tool that made the pattern. Simple transfer patterns are produced when the bloody object makes contact with a surface and the object is removed without any further movement. Other transfers known as "swipe patterns" may be caused by movement of the bloody object across a surface. Generally, the pattern will lighten and "feather" as the pattern moves away from the initial contact point. However, because "feathering" is also a function of the amount of pressure being applied to the surface, the analyst must interpret directionality with care. The direction of separate bloody transfers, such as footwear prints in blood, may show the movement of the suspect, victim, or others through the crime scene after the blood was present. The first transfer pattern will be dark and heavy with blood, whereas subsequent transfers will be increasingly lighter in color. The transfers get lighter as less and less blood is deposited from the transferring object's surface. Bloody shoe imprints may also suggest whether the wearer was running or walking. Running typically produces imprints with more space between them and more satellite or drop patterns between each imprint.

Blood spatter patterns of any kind can provide...

a great deal of information about the events that took place at a crime scene.

Only some jurisdictions have

a specialist on staff to decipher patterns either at the scene or from photographs at the lab. Therefore, it is important that all personnel be familiar with patterns to properly record and document them for use in reconstruction.

Satellite spatter around parent stains will have the pointed end facing...

against the direction of travel.

Low-velocity spatter

is created by a force traveling at 5 feet per second or less and producing drops with diameters of greater than 4 millimeters. consisting of a preponderance of large, separate, or compounded drops This kind of spatter is normally produced by gravity alone, by a minimal force, or by an object dropping into and splashing blood from a blood pool. Low-velocity stains can result from an applied force moving at up to 5 feet per second.

Using droplet size to classify impact patterns by velocity is a useful tool that

gives investigators insight into the general nature of a crime. However, the classifications of low, medium, and high velocity cannot illuminate the specific events that produced the stain pattern. For example, beatings can produce either high-velocity spatter or stain sizes that look more like low-velocity spatter. In general, one should use stain size categories very cautiously, and for descriptive purposes only, in evaluating impact spatter patterns. A more acceptable approach for classifying a bloodstain pattern should encompass observations of stain size, shape, location, and distribution.