Blood Spatter in ForensicsBlood Spatter in Forensics

General Bloodstain FeaturesGeneral Bloodstain Features

Bloodstain patterns deposited on floors, Bloodstain patterns deposited on floors, walls, bedding, and other relevant objects walls, bedding, and other relevant objects can provide valuable insights into events can provide valuable insights into events that occurred during the commission of a that occurred during the commission of a violent crime. violent crime.

The crime scene investigator must The crime scene investigator must remember that the location, distribution, remember that the location, distribution, and appearance of bloodstains and spatters and appearance of bloodstains and spatters may be useful for interpreting and may be useful for interpreting and reconstructing the events that produced the reconstructing the events that produced the bleeding.bleeding.

General Bloodstain FeaturesGeneral Bloodstain Features The information one is likely to uncover as a result of The information one is likely to uncover as a result of

bloodstain pattern interpretation includes:bloodstain pattern interpretation includes:

-- The direction from which blood originated-- The direction from which blood originated

-- The angle at which a blood droplet struck a -- The angle at which a blood droplet struck a surface surface

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

-- The movement of a bleeding individual at the -- The movement of a bleeding individual at the crime crime scenescene

-- The approximate number of blows that struck a -- The approximate number of blows that struck a bleeding victimbleeding victim

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

Importance of Blood SpatterImportance of Blood Spatter

More than just DNAMore than just DNA Can be used to reconstruct the crimeCan be used to reconstruct the crime Can place a suspect at the scene of Can place a suspect at the scene of

the crimethe crime Has been used to gain acquittalsHas been used to gain acquittals

Effects of Surface TextureEffects of Surface Texture

Surface texture and the stain’s Surface texture and the stain’s shape, size, and location must be shape, size, and location must be considered when determining the considered when determining the direction, dropping distance, and direction, dropping distance, and angle of impact of a bloodstain.angle of impact of a bloodstain.

Surface texture is of paramount Surface texture is of paramount importance. In general, the harder importance. In general, the harder and less porous the surface, the less and less porous the surface, the less spatter results.spatter results.

Categories of Blood StainsCategories of Blood Stains

PassivePassive: drops formed or created by : drops formed or created by gravitational force alonegravitational force alone

TransferTransfer: created by a wet, bloody : created by a wet, bloody surface coming into contact with surface coming into contact with another surface often leaving a another surface often leaving a recognizable image of all or a portion recognizable image of all or a portion of the initial surfaceof the initial surface

ProjectedProjected: created by a force or : created by a force or action greater than that of gravityaction greater than that of gravity

Passive StainsPassive Stains

Affected primarily Affected primarily by surface texture by surface texture and height of and height of dropletdroplet

The greater the The greater the distance from distance from origin to surface origin to surface the more spatter the more spatter createdcreated

Transfer PatternTransfer Pattern

A A contactcontact or or transfer patterntransfer pattern is created is created when an object with blood on it touches one when an object with blood on it touches one that does not have blood on it.that does not have blood on it.

Simple transfer patterns are produced when Simple transfer patterns are produced when the object makes contact with the surface and the object makes contact with the surface and is removed without any movement of the is removed without any movement of the object. object.

The size and general shape of the object may The size and general shape of the object may be seen in a simple transfer. be seen in a simple transfer.

Other transfers may be caused by movement Other transfers may be caused by movement of the bloody object across a surface. of the bloody object across a surface.

Transfer StainsTransfer Stains

Can create measurable images such Can create measurable images such as footprintsas footprints

Can leave an identifiable impression Can leave an identifiable impression such as a finger or palm printsuch as a finger or palm print

Transfer Stains Cont.Transfer Stains Cont.

Projected Blood StainsProjected Blood Stains

Size, shape, and Size, shape, and number of stains is number of stains is dependant on the dependant on the amount of force amount of force exerted on the exerted on the blood sourceblood source

Often creates cast Often creates cast off patternsoff patterns

Impact SpatterImpact Spatter

Low Velocity: Up to 5 ft/secLow Velocity: Up to 5 ft/sec Stains 4mm or greaterStains 4mm or greater Medium Velocity: 5-25 ft/secMedium Velocity: 5-25 ft/sec Stains 1-4mmStains 1-4mm High Velocity: 100+ ft/secHigh Velocity: 100+ ft/sec Stains less than 1mm usually mist Stains less than 1mm usually mist

like appearancelike appearance

Low Velocity SpatterLow Velocity Spatter

Medium Velocity SpatterMedium Velocity Spatter

High Velocity SpatterHigh Velocity Spatter

Impact Bloodstain Spatter Impact Bloodstain Spatter PatternsPatterns

Impact spatter occurs when an Impact spatter occurs when an object impacts a source of blood. object impacts a source of blood.

Forward spatter Forward spatter is projected is projected outward and away from the source. outward and away from the source.

Back spatterBack spatter, sometimes called , sometimes called blow-back spatter, is projected blow-back spatter, is projected backward from the source, backward from the source,

Gunshot SpatterGunshot Spatter

Gunshot spatter is characterized by fine Gunshot spatter is characterized by fine forward spatter from an exit wound and forward spatter from an exit wound and back spatter from an entrance wound. back spatter from an entrance wound. However, the gunshot produces only back However, the gunshot produces only back spatter if the bullet does not exit the body. spatter if the bullet does not exit the body.

Depending upon the distance from the Depending upon the distance from the victim that the gun was discharged, some victim that the gun was discharged, some back spatter may strike the gunman and back spatter may strike the gunman and enter the gun muzzle. This is called the enter the gun muzzle. This is called the drawback effectdrawback effect. .

Cast-off SpatterCast-off Spatter A A cast-off cast-off pattern is created when a blood-pattern is created when a blood-

covered object flings blood in an arc onto a covered object flings blood in an arc onto a nearby surface. nearby surface.

This kind of pattern commonly produced by This kind of pattern commonly produced by a bloody fist or weapon between delivering a bloody fist or weapon between delivering blows.blows.

The features of the cast-off pattern are The features of the cast-off pattern are affected by the size of the object, the affected by the size of the object, the amount of blood, and the direction the amount of blood, and the direction the object was moving.object was moving.

By counting and pairing forward/backward By counting and pairing forward/backward patterns, one may determine the patterns, one may determine the minimum minimum number of blows delivered. number of blows delivered.

Evidence Derived from Cast Off Evidence Derived from Cast Off Patterns Patterns

Position of assailant and victim Position of assailant and victim during attackduring attack

Direction weapon traveled Direction weapon traveled Approximate height of attackerApproximate height of attacker Impact angle of spatterImpact angle of spatter Point of convergencePoint of convergence

Arterial Spray SpatterArterial Spray Spatter Arterial sprayArterial spray spatter is created when a spatter is created when a

victim suffers an injury to a main artery or victim suffers an injury to a main artery or the heart, and the pressure of the the heart, and the pressure of the continuing pumping of blood causes blood continuing pumping of blood causes blood to spurt out of the injured area.to spurt out of the injured area.

The site of the initial injury to the artery The site of the initial injury to the artery can be found where the pattern begins can be found where the pattern begins with the biggest spurt. The trail away from with the biggest spurt. The trail away from this point shows the victim’s movement. this point shows the victim’s movement.

The oxygenated blood spurting from the The oxygenated blood spurting from the artery tends to be a brighter red color artery tends to be a brighter red color than blood expelled from impact wounds. than blood expelled from impact wounds.

Cast Off Vs. Arterial SpurtingCast Off Vs. Arterial SpurtingCast off is created by force or Cast off is created by force or action greater than gravityaction greater than gravity

Arterial spurting is created when blood exits Arterial spurting is created when blood exits the body under pressure from a the body under pressure from a compromised arterycompromised artery

Expirated Blood PatternsExpirated Blood Patterns

An An expirated blood patternexpirated blood pattern is created by is created by blood that is expelled from the mouth or blood that is expelled from the mouth or nose from an internal injury.nose from an internal injury.

The presence of bubbles of oxygen in the The presence of bubbles of oxygen in the drying drops or a lighter color as a result of drying drops or a lighter color as a result of dilution by saliva can differentiate a pattern dilution by saliva can differentiate a pattern created by expirated blood.created by expirated blood.

The presence of expirated blood gives an The presence of expirated blood gives an important clue as to the injuries suffered and important clue as to the injuries suffered and the events that took place at a crime scene.the events that took place at a crime scene.

Void PatternVoid Pattern A A voidvoid is created when an object blocks is created when an object blocks

the deposition of blood spatter onto a the deposition of blood spatter onto a target surface or object and the spatter target surface or object and the spatter is deposited onto the object or person is deposited onto the object or person instead. instead.

The blank space on the surface or object The blank space on the surface or object may give a clue as to the size and shape may give a clue as to the size and shape of the missing object or person. of the missing object or person.

Voids may be applicable for establishing Voids may be applicable for establishing the body position of the victim or the body position of the victim or assailant at the time of the incident.assailant at the time of the incident.

Flow PatternsFlow Patterns Flow patterns Flow patterns are made by drops or large are made by drops or large

amounts of blood flowing by the pull of amounts of blood flowing by the pull of gravity.gravity.

““Active” flows are formed by blood coming Active” flows are formed by blood coming from an actively bleeding wound.from an actively bleeding wound.

““Passive” flows originate with blood deposited Passive” flows originate with blood deposited on a surface such as an arterial spurt. on a surface such as an arterial spurt.

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

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

Pool PatternsPool Patterns

AA pool pool of blood occurs when blood collects in of blood occurs when blood collects in a level and undisturbed place.a level and undisturbed place.

Blood that pools on an absorbent surface Blood that pools on an absorbent surface may be absorbed throughout the surface and may be absorbed throughout the surface and diffuse.diffuse.

The approximate drying time of a pool of The approximate drying time of a pool of blood is related to the environmental blood is related to the environmental condition of the scene. By experimentation condition of the scene. By experimentation an analyst may be able to reasonably an analyst may be able to reasonably estimate the drying times of stains of estimate the drying times of stains of different sizes. different sizes.

SkeletonizationSkeletonization

The phenomenon of The phenomenon of skeletonization skeletonization occurs occurs when the edges of a stain dry to the surface.when the edges of a stain dry to the surface.

This usually occurs within 50 seconds of This usually occurs within 50 seconds of deposition of droplets, and longer for larger deposition of droplets, and longer for larger volumes of blood. volumes of blood.

After this time, if the bloodstain is altered by a After this time, if the bloodstain is altered by a contact of wiping motion, the skeletonized contact of wiping motion, the skeletonized perimeter will be left intact.perimeter will be left intact.

Knowing the skeletonization time, an Knowing the skeletonization time, an investigator determine the timing of movement investigator determine the timing of movement or activity.or activity.

Trail PatternTrail Pattern AA trail trail patternpattern is a series of drops that are is a series of drops that are

separate from other patterns, formed by separate from other patterns, formed by blood dripping off an object or injury. blood dripping off an object or injury.

The stains form a kind of line or path The stains form a kind of line or path usually made by the suspect after injuring usually made by the suspect after injuring or killing the victim or injuring themself. or killing the victim or injuring themself.

The pattern may show movement, lead to a The pattern may show movement, lead to a discarded weapon, or provide identification discarded weapon, or provide identification of the suspect by his or her own blood. of the suspect by his or her own blood.

The shape of the stains in trail patter can The shape of the stains in trail patter can help investigators determine the direction help investigators determine the direction and speed at which a person was moving. and speed at which a person was moving.

Determining the Impact AngleDetermining the Impact Angle

Pointed end of blood Pointed end of blood stain always faces its stain always faces its direction of traveldirection of travel

Measure the degree of Measure the degree of circular distortion to circular distortion to determine impact determine impact angleangle

As the angle As the angle decreases the stain decreases the stain becomes increasingly becomes increasingly elongatedelongated

Area of ConvergenceArea of Convergence

The The area of convergencearea of convergence is the is the point on a two-dimensional plane point on a two-dimensional plane from which the drops in an impact from which the drops in an impact pattern originated. pattern originated.

This can be established by drawing This can be established by drawing straight lines through the long axis of straight lines through the long axis of several individual bloodstains, several individual bloodstains, following the line of their tails. following the line of their tails.

Point of Convergence Cont.Point of Convergence Cont.Forensic Team uses string to Forensic Team uses string to identify originidentify origin Illustration of ConvergenceIllustration of Convergence

Point of ConvergencePoint of Convergence

Point of Point of convergence is convergence is identified by identified by drawing a line drawing a line through the long through the long axis of a stainaxis of a stain

The point at which The point at which the stains the stains converge is the converge is the blood spatter originblood spatter origin

Area of OriginArea of Origin The The area of originarea of origin of an impact of an impact

bloodstain pattern is the area in a bloodstain pattern is the area in a three-dimensional space from which three-dimensional space from which the blood was projected.the blood was projected.

This will show the position of the This will show the position of the victim or suspect in space when the victim or suspect in space when the stain-producing event took place. stain-producing event took place.

The string method is commonly used The string method is commonly used at a crime scene to approximate the at a crime scene to approximate the position of the area of origin using position of the area of origin using found angles of impact of individual found angles of impact of individual stains in the pattern.stains in the pattern.

Documenting Bloodstain EvidenceDocumenting Bloodstain Evidence

Investigators should note, study, and Investigators should note, study, and photograph each pattern and drop to photograph each pattern and drop to accurately record the location of specific accurately record the location of specific patterns and to distinguish the stains from patterns and to distinguish the stains from which laboratory samples were taken.which laboratory samples were taken.

In photographs specific techniques are In photographs specific techniques are used to document bloodstain patterns.used to document bloodstain patterns.-- The -- The grid methodgrid method involves setting up a involves setting up a grid of squares grid of squares of known dimensions of known dimensions over the entire pattern. over the entire pattern. -- The -- The perimeter ruler methodperimeter ruler method involves involves setting up a rectangular border of rulers setting up a rectangular border of rulers around the pattern and then placing a around the pattern and then placing a small ruler next to each stain. small ruler next to each stain.

Interpreting Bloodstain EvidenceInterpreting Bloodstain Evidence

Some jurisdictions have a specialist Some jurisdictions have a specialist on staff who will decipher patterns on staff who will decipher patterns either at the scene or from either at the scene or from photographs at the lab.photographs at the lab.

However, it is important that However, it is important that allall personnel be familiar with patterns to personnel be familiar with patterns to properly record and document them properly record and document them for use in reconstruction. for use in reconstruction.

Questions ?Questions ?