Angle of Impact
The acute angle (alpha), relative to the plane of a target, at which a blood drop strikes the target.
Arterial spray
a characteristic blood stain pattern containing spurts that resulted from blood exiting under pressure from an arterial injury
Back spatter
blood directed back toward the source of the force that caused the spatter
Cast off
a bloodstain pattern that is created when blood is flung from a blood bearing object in motion onto a surface
Crime scene reconstruction
the method used to support a likely sequence of events at a crime scene by the observation and evaluation of physical evidence and statements made by individuals involved with the incident
Drip trail pattern
a pattern of blood stains formed by the dripping of blood off a moving surface or person in a recognizable pathway separate from other patterns
Expirated blood pattern
a pattern created by blood that is expelled out of the nose, mouth, or respiratory system as a result of air pressure and/or air flow
Flow patterns
a bloodstain pattern formed by the movement of small or large amounts of blood as a result of gravity's pull
Forward spatter
blood that travels away from the source in the same direction that caused the spatter
High velocity spatter
an impact spatter pattern created by a force traveling at 100 feet per second or faster and producing drops with diameters less than 1 millimeter
Medium velocity spatter
an impact spatter pattern created by a force traveling at 5 to 25 feet per second and producing drops with diameters between 1 and 3 millimeters
Low velocity spatter
an impact spatter pattern created by a force traveling 5 feet per second or less and producing drops with diameters greater than 3 millimeters
Luminol
this chemical is used by crime scene investigators to locate traces of blood, even if it has been cleaned or removed. Investigators spray a luminal solution is throughout the area under investigation and look for reactions with the iron present in blood,
Origin/Source
the place from which the blood spatter came from or originated
Parent drop
the droplet from which a satellite spatter originates
Passive Blood stains
patterns created from the force of gravity
Point (Area) of Convergence
the area on a two dimensional plane where lines traced through the long axis of several individual bloodstains meet
Point (Area) of origin
the location in three dimensional spaces from which blood that produced a blood stain originated
Projected Bloodstains
patterns that occur when the force is applied to the source of the blood
Satellite Spatters
small drops of blood that are distributed around the perimeter of a drop or pool of blood and were produced as a result of the blood impacting the target surface
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
Skeletonization
the process by which the edges of a stain dry to the surface in a specific period of time
Swipe
The transfer of blood from a moving source onto an unstained surface.
Wipe
A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance.
Blood Spines
the pointed edge of the stain that radiates out from the spatter; can help determine the direction from which the blood traveled
Transfer (Contact) Bloodstains
A bloodstain pattern created when a wet, bloody surface comes in contact with a second surface. A recognizable image of all or portion of the original surface may be observed in the pattern.
Void
An absence of strains in an otherwise continuous bloodstain pattern
History of Blood Spatter Analysis
1894 - Pitoroski wrote the earliest reference to blood spatter
1939 - Balthazard first researcher to analyze the meaning of spatter pattern
1955 - blood spatter evidence used in the Sam Shepard case, helping to exonerate him
1971 - Dr. Herbert McDonnell u
Blood Spatter Analysis-What can a forensic scientist learn from blood spatter analysis
1. Origin(s) of bloodstain
2. Distance of bloodstain from target
3. Direction from which blood impacted
4. Speed with which blood left its source
5. Position of victim & assailant
6. Movement of victim & assailant
7. Number of blows/shots
How blood drops look on porous vs. nonporous surface
hard, smooth, nonporous surface, it will create very little spatter so the edges of the blood spatter will be round and smooth.
porous, rough surface, it tends to spatter more so the drops of blood will be jagged or have spikes around the edges.
Blood stain shape vs. AOI
A drop deposited at an angle of impact of 90 degrees will be circular in shape with no tail or buildup of blood. As the angle of impact gets smaller the stain becomes elongated in shape
Identify blood stains of walking vs. running
Walking has a more circular blood stain while running has a blood stain that is more elongated
Calculate Angle of Impact
AOI= inverse sine (w/l)
Lines of Convergence
found by drawing straight lines down the long axis of blood spatter and noting where they intersect
Calculate height of blood spatter origin
Horizontal distance x tan(AOI)
Point of Origin
lies at a point in space above the point of convergence.
Measurement of the impact angle allows for translation of the 2-D image (convergence) into a 3-D one (origin).
Percent Error
|ACCEPTED-EXPERIMENTAL/ACCPTED| X 100