Knowt0.0(0)
Tags
Note
Studied by 465 people
Forensics Unit 7 Notes
- What is Blood Spatter Analysis?
- The examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin.
- What can we learn from blood spatter?
- Mechanism that created the stains
- Direction a blood droplet was traveling
- Area of origin
- Type of object used in attack
- Minimum number of blows
- Presence of a subject at a scene
- Positioning of the victim, suspect and objects during events
- Sequence of events
- BLOOD SPATTER – BRIEF HISTORY
- PAUL L. KIRK FATHER OF BLOOD SPATTER ANALYSIS
- SAM SHEPPARD CONVICTED OF MURDERING HIS WIFE 1955
- 1 month after the conviction, Kirk analyzed the blood spatter.
- The case was retried in 1966 and Sheppard was acquitted.
- Kirk was never admitted into the AAFS.
- TYPES OF STAINS:
- PASSIVE
- Large blood pools or drips of blood formed from the force of gravity acting alone. (stain is larger than 4 mm in diameter)
- Should make sense in terms of gravity and location of the body. (Was the body moved?)
- Blood dripping into a pool of blood
- Person walking versus Standing still
- TRANSFER
- Shoe prints are a common transfer pattern. The order of the shoeprints can be determined as each print gets lighter. Chemicals can be used to detect minute quantities of blood, produced from up to 200 footsteps.
- Produced when an object with blood on it comes into contact with an object or a surface that does not have blood on it = SWIPE and WIPE
- Swipe: The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge.
- Wipe: A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance. The ring of blood you see is called skeletonization; it is hardened blood that develops 50 seconds after spatter, and is the hardest part of a stain to clean.
- PROJECTED
- RADIAL SPATTER – blood produced from a bludgeoning radiates from the origin except where the perpetrator was standing. (the blood is on the perpetrator) This is called a VOID.
- CAST OFF SPATTER – used to determine the minimum number of blows in a bludgeoning.
- Arterial Spurting or Gushing: Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery.
- PASSIVE
- DETERMINING the TYPE OF FORCE that caused the blood spatter
- The force (and height) behind the production of spatter will influence the diameter of the stain.
- LOW VELOCITY >4mm Dripping
- MEDIUM VELOCITY 1-4 mm Bludgeoning
- HIGH VELOCITY <1mm Gunshot Expired blood (coughed up)
- Fly Spots
- Flies are little pigs with wings and like to soak up crime scene blood. But they can’t hold it in! So you may see some spots of blood (such as on a windowsill) that could be from a fly regurgitating blood. Don’t assume anything in forensic science!!
- How does surface affect the shape of the stain?
- Rough surfaces produce satellite spatter.
- How does height affect the shape of the stain?
- The stain increases in diameter as height increases.
- DETERMINING THE ORIGIN OF THE BLOOD SHED
- Blood droplets in freefall have the shape of a sphere.
- The tail tells DIRECTION the blood was traveling.
- Calculating the ANGLE of IMPACT.
- Sin x=width/length
- Find the AREA of CONVERGENCE.
- Stringing method: Compare the victim wounds to area of origin to determine the position of the victim
- Tangent Formula: height=tan(angle)*distance
- COLLECTING & PRESERVING BLOOD SPATTER EVIDENCE
- Like any other evidence, document with notes, sketches and photography.
- Each stain must be packaged separately!!
- Do reconstruction before collecting evidence and cleaning up.
- Allow stain to dry and package in paper.
- Blood Stain Drying Times
- Being able to estimate the time the blood was shed is useful in reconstructing the crime. The environment has a huge influence on how fast the blood will dry. The temperature, humidity, Direction of the wind, Speed of the wind, the type of surface, the temperature of the surface all influence how fast the stain will dry.
- Blood Stain Reconstructions
- Often the forensic scientist will perform experiments to try and recreate the blood spatter patterns. Fresh whole blood must be used in these experiments because unlike any other fluid, blood clots and becomes thicker as it dries which slows the overall drying significantly.
- Often the forensic scientist will perform experiments to try and recreate the blood spatter patterns. Fresh whole blood must be used in these experiments because unlike any other fluid, blood clots and becomes thicker as it dries which slows the overall drying significantly.
Forensics Unit 7 Notes
- What is Blood Spatter Analysis?
- The examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin.
- What can we learn from blood spatter?
- Mechanism that created the stains
- Direction a blood droplet was traveling
- Area of origin
- Type of object used in attack
- Minimum number of blows
- Presence of a subject at a scene
- Positioning of the victim, suspect and objects during events
- Sequence of events
- BLOOD SPATTER – BRIEF HISTORY
- PAUL L. KIRK FATHER OF BLOOD SPATTER ANALYSIS
- SAM SHEPPARD CONVICTED OF MURDERING HIS WIFE 1955
- 1 month after the conviction, Kirk analyzed the blood spatter.
- The case was retried in 1966 and Sheppard was acquitted.
- Kirk was never admitted into the AAFS.
- TYPES OF STAINS:
- PASSIVE
- Large blood pools or drips of blood formed from the force of gravity acting alone. (stain is larger than 4 mm in diameter)
- Should make sense in terms of gravity and location of the body. (Was the body moved?)
- Blood dripping into a pool of blood
- Person walking versus Standing still
- TRANSFER
- Shoe prints are a common transfer pattern. The order of the shoeprints can be determined as each print gets lighter. Chemicals can be used to detect minute quantities of blood, produced from up to 200 footsteps.
- Produced when an object with blood on it comes into contact with an object or a surface that does not have blood on it = SWIPE and WIPE
- Swipe: The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge.
- Wipe: A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance. The ring of blood you see is called skeletonization; it is hardened blood that develops 50 seconds after spatter, and is the hardest part of a stain to clean.
- PROJECTED
- RADIAL SPATTER – blood produced from a bludgeoning radiates from the origin except where the perpetrator was standing. (the blood is on the perpetrator) This is called a VOID.
- CAST OFF SPATTER – used to determine the minimum number of blows in a bludgeoning.
- Arterial Spurting or Gushing: Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery.
- PASSIVE
- DETERMINING the TYPE OF FORCE that caused the blood spatter
- The force (and height) behind the production of spatter will influence the diameter of the stain.
- LOW VELOCITY >4mm Dripping
- MEDIUM VELOCITY 1-4 mm Bludgeoning
- HIGH VELOCITY <1mm Gunshot Expired blood (coughed up)
- Fly Spots
- Flies are little pigs with wings and like to soak up crime scene blood. But they can’t hold it in! So you may see some spots of blood (such as on a windowsill) that could be from a fly regurgitating blood. Don’t assume anything in forensic science!!
- How does surface affect the shape of the stain?
- Rough surfaces produce satellite spatter.
- How does height affect the shape of the stain?
- The stain increases in diameter as height increases.
- DETERMINING THE ORIGIN OF THE BLOOD SHED
- Blood droplets in freefall have the shape of a sphere.
- The tail tells DIRECTION the blood was traveling.
- Calculating the ANGLE of IMPACT.
- Sin x=width/length
- Find the AREA of CONVERGENCE.
- Stringing method: Compare the victim wounds to area of origin to determine the position of the victim
- Tangent Formula: height=tan(angle)*distance
- COLLECTING & PRESERVING BLOOD SPATTER EVIDENCE
- Like any other evidence, document with notes, sketches and photography.
- Each stain must be packaged separately!!
- Do reconstruction before collecting evidence and cleaning up.
- Allow stain to dry and package in paper.
- Blood Stain Drying Times
- Being able to estimate the time the blood was shed is useful in reconstructing the crime. The environment has a huge influence on how fast the blood will dry. The temperature, humidity, Direction of the wind, Speed of the wind, the type of surface, the temperature of the surface all influence how fast the stain will dry.
- Blood Stain Reconstructions
- Often the forensic scientist will perform experiments to try and recreate the blood spatter patterns. Fresh whole blood must be used in these experiments because unlike any other fluid, blood clots and becomes thicker as it dries which slows the overall drying significantly.
- Often the forensic scientist will perform experiments to try and recreate the blood spatter patterns. Fresh whole blood must be used in these experiments because unlike any other fluid, blood clots and becomes thicker as it dries which slows the overall drying significantly.
0.0(0)
Tags
