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SCIENTIFIC APPROACHES IN BLOODSTAIN ANALYSIS December 2011 William Y. K.…
SCIENTIFIC APPROACHES IN BLOODSTAIN ANALYSIS
December 2011
William Y. K. Trumbo
Chapter 1
Study Background
fraudulent lab findings, analysts were investigated.
history of exonerated convictions due to false bloodstains reports
purpose/objectives
examine scientific methodology
a. physical properties of blood
b. velocities of blood spatter
c. theory of blood spatter and angle of impact determination
d. documentation of bloodstain at the crime scene.
(a) type of velocity of the weapon used,
(b) number of blows inflicted,
(c) position and movements of victim and assailant during the attack, (d) type of injuries,
(e) when crime was committed,
(f) which wound was inflicted first.
Rationale
bloodstains provides forensic investigators with important information when
conducting a criminal investigation
based on principles
derived from: biology, chemistry, physics, and mathematics
project seeks to explore methodological
bloodstain analyses that yield reliable and verifiable evidentiary findings
Hypothesis and Limitations
Limitations to this study include subjective research-based
methods and findings
first hypothesis: calculating the angle of impact of blood droplets yield conclusive findings about
origination of blood
second hypothesis: blood mist is usually caused by gunshot injuries
third hypothesis: bloodstain analysis by proxy utilizing photographic documentation reveals causations of bloodstains.
Chapter 2
Serology
Serologist perform test to analyze other bodily fluids found at the crime scene, such as urine or semen
determines the blood
type found at the crime scene
both class and individual characteristics for comparison
have long been able to identify the presence of sperm and semen by testing for acid phosphates or by microscopic examination for sperm cells
saliva is present by testing for the presence of amylase or starches and they can distinguish between other body fluids
Biology
Blood is a tissue that is circulated within the body to assist other parts of the body
Blood consists of fluids called plasma and three types of blood cells: red, white, and platelets.
Plasma, which makes up fifty-five percent of our blood
Erythrocytes also known as red blood cells, carry oxygen
Leukocytes also found in blood are known as white blood cells, helps our bodies fight off infections and diseases
Blood Groups: Type A blood has type
A antigens on its surface, Type B blood has type B antigens, Type AB blood has both type A and B on its surface, Type O blood does not have either type A or B antigens on its surface
primary function of blood is to supply oxygen to tissues throughout the body, remove waste such as carbon dioxide, urea, and lactic acid, and regulate core body temperature and ph- levels, and transport hormones throughout the body while circulating white blood cells and antigens to repair the body
Viscosity
blood is four times more viscous than water
Blood viscosity is determined by the ratio of hemoglobin to
whole blood: the hematocrit
y=v/h
blood flight
density of blood plasma is approximately 1025kg/cm3
density of blood cells circulating in the blood is approximately 1125 kg/m3
equation can be expressed as y = ax^2 bx + c
Shape of the stains vary from ovular and circular, the impact angles too vary from 0 degrees to less than 90 degrees
Chapter 3
Angle of Impact
measuring the length and width of the splatter, dividing the width of the splatter by its length, we can determine the impact angle
(a) measure the length and width of the blood stain; (b)
divide the width of the blood stain by its length and (c) determine the arcsine of that number, typically using a calculator with an arcsine function
angle of impact = arc sin W/L
By locating the source in a three- dimensional space, the height of blood source above the point of convergence can be calculated
Case Study 1
elderly woman was raped
DNA evidence also was recovered at that scene and matched DNA in the January 2000 case
The DNA evidence matched the two previous cases
investigators discovered: Victim’s Body, Blood, Blood Spatter
Forensic analyst can manually calculate the point of convergence through a method called the stringing method
Chapter 4
Objects that cause low velocity stains can include a blunt force tool or a person's fists inflicting a blow
blood stain: .39 arc sine
Medium velocity bloodstains can be associated with objects that produce external forces of greater than 5ft/sec and less than 25ft/sec.
High velocity bloodstains can be associated with objects such as a gun or any object producing an external force of 100 feet-per-second or greater as shown in Figure 4-3
The Department of Neurosurgery present studies on gunshot wounds to the head have demonstrated a male predominance
Multiple spatters indicate, repeated trauma a victim has underwent, in which bloodshed has occurred repeatedly
Bloodstain Interpretation
Bloodstains can be classified as low velocity, medium velocity or high velocity impact stains
Velocity essentially, describes the amount of force and energy that is directed upon a
specific blood source which creates the stain
The stringing method involves the following
processes: the analyst first determines the location of the stain and calculates the angle of impact
Adkin‟s research on low velocity stains include bloodstains are produced by an external
force less than 5 feet-per-second (normal gravity) and the stains are 4mm and larger
Chapter 5
Bloodstain analysis by proxy utilizing photographic documentation reveals causations of bloodstains
close-up photograph should be taken at a 90 degree angle to the position of the object
If bloodstains are wet, they must be all dried prior to packaging
UNDER NO CIRCUMSTANCES SHOULD EVIDENCE CONTAINING MOISTURE BE PACKAGED IN PLASTIC OR PAPER CONTAINERS FOR MORE THAN TWO HOURS
The packages or containers must be sealed and secured to minimize contamination of evidence during transportation
the final step in documenting bloodstains evidence is establishing the chain of custody.
A reliable chain of custody documents the transporting and relocating
of evidence.
Conclusion
Forensic science or forensics is the scientific processing of information found at the
crime scene
Blood is one of the most common types of physical evidence found at a crime scene.
The project examined the first hypothesis: calculating the
angle of impact of blood droplets yield conclusive findings about origination of blood.
Recommendations
Crime scene forensics will not always win and supplement a case, but excellent forensic investigation, interpretations, and analysis, will make a case better to solve
DNA analysis or DNA testing has significantly advanced within the last decades.
DNA profiling gives the forensic technician the ability to test specific encrypted
sets of DNA sequences, which can be obtained from semen, blood, salvia
Restriction Fragment Length Polymorphism analysis (RFLP)testing allows scientist to detect genetic traits and specific genetic characteristics
PCR analysis can now amplify the ability to recover information from small reference samples
Another great advancement in crime scene processing is the accessibility of adequate investigates tools utilized to document the scene
Documentation of the crime scene visually, preserves the evidence so that it can
be presented to attorneys
Forensics will benefit as the evidence derived becomes
reliable
