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cains murder of able
who was first murder
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48 hours
- homicide investigation crucial timeframe
- chances cut in half if not solved in the time frame
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typical steps in a homicide investigation
- process the crime scene
- identifiy the victim
- est. cause, manner, and time of death
- ascertain a motive
- identify suspect(s)
- gather evidence against suspect
- present the case to the prosecutor
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the crime scene
the victim
the suspect
to the physical evidence
we want to link
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crime scene staging
the perpetrator purposely alters the crime scene to mislead authorities and/ or redirect the investigation
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Crime scene staging
- does not include actions of family members who dress or cover a loved one
- most common make murder appear to be suicide or accident
- others: making the murder appear to be sex related arson to appear accidental
- may indicate realtionship
- RISKY BEHAVIOR
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forensic pathologist
medical doctors who investigate cause, manner, and time of death in suddenm unnatural, unexplained, or violent deaths
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accelerated, stopped
Decompostition is ....... by heat, and .....by freezing
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rigor mortis
- the stiffeing of the muscles after death
- onset 2-4 hours after death
- disappear within 18-36 hours
- completely gone within 48-60 hours
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Livor Mortis
- the settleing of the blood in the dependent areas of the body after death
- heart ceases to pump and gravity takes over onset in 30 mins. fixed will not blanch and will not change around 8-10 hours
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ocular fluid
potassium levels in vireous humor
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gastrointestional tract contents
under ordinary circumstances the stomach empties its content 4-6 hours after a meal
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abrasions
removal of the superficial layers of the skin by friction of compression
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contusion
brushing area of hemorrhage into soft tissue
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lacerations
tear in the tissue by shearing or crushing force
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stab wounds
depth exceeds the length
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incised wounds
cuts, length is greater then its depth
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blunt force trama wounds
- abrasions
- contusion
- laceration
- fractures
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sharp force trauma wounds
- stab wounds
- incised wounds
- chop wounds
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Asphyxia
- failure of cells to receive or utilize oxygen
- can be seen in drowning
- inhalation of poison gases
- suffocation
- stangulation
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petechial hemorrhages
pinpoint blood clots produced by the rupture of small vessels
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entrance wound
round hole with abrasion collar smaller then other
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exit whole
ragged and torn appearence generally larger then other whole
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tattooing
pinpoint hemorrhages due to burned powder, unburned powder driven into skin cant be wiped off
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smudging/ fouling
- from soot and smoke around wound
- easily wiped off
- indicates a close shot but not contact
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fratricide
killing your brother
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1. homicide
2. suicide
3. accident
4. natural
5. undetermined
5 manners of death
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mass murder
done in one location, targeted violence attacker selects specific target.
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forensic anthropology
concerned with the identification and examination of human skeletal remains
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Peroxidases
- Enzymes that accelerate the oxidation of several classes of
- origin compounds when combined with peroxide
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Bloodstain + Reagent+ hydrogen peroxide=
oxidation of thehemoglobin and a color change.
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Kastle Meyer color test
phenolphthalein –color change is pink
- Highly indicative but not specific for blood some vegetable matter will
- lead to false positive (ex. Potatoes and horseradish
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1. distilled water
2.swab stain
3.phenolphthoin
4.hydrogen peroxide
5.pink color= positive result
How to do the kestle meyer test
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Luminal and bluestar
- Only when blood has been cleaned up or hidden presumptive
- Light producing reaction called chemiluminescence emits
- light blue color reacts with the hemoglobin
- Need darken room captured with photography swabs collected
- from area for potential DNA
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Preciptin tests
Used to test if it is human or animal blood
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Semen
- Searching for dried seminal stains
- 1.visual
- 2. Alternate light source (ALS) provides high intense light
- through fibers
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ALS (alternative light souse)
- Some substances fluoresces when excited by a particular
- range of light
- The material absorbs the exciting light and remits light at
- longer wavelengths (stokes shift)
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Testing for seminal stains
Acid phosphatase color contest (AP)
- Acid phosphatase is an enzyme secreted by the postate glad
- into semial fluid
Positive=blue color 30 seconds or longer
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Polymerase chain reaction (PCR)
- A technique for replicating or copying a portion of a DNA
- strand
Short tandem repeats (STR)
- A region of a DNA molecule that contains short segments of
- repeating base pairs
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Probability of identity
- A measure of likelihood that two individuals selected at
- random will have the identical STR type
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Mitochondrial DNA
- DNA found outside the nucleus
- Inherited sole from the mother
- All individuals of the same material lineage will be
- indistinguishable
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Wear gloves
Change them often
In between different samples
Avoid talking, sneezing, coughing, over evidence
Wear face masks for tough DNA
Do not store in hot locations (trunk)
Package in paper NEVER PLASTIC
Air dry- if wet
Collection of DNA
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Crime scene reconstruction
- 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 incident
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1.free of expectation of bias
2.continually re-evaluate data
3.have independent peer review
Objectivity manner of professional detachment
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deductive reasoning
- the process of drawing a conclusion based on known facts or
- premises
(e.g. fingerprints on table=victim touched table) concrete evidence
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inductive reasoning
- the process of drawing a conclusion from the premises one
- does not know are correct
- (conclusion is probable but not definitive e.g. large pool
- of blood at a scene =victim probably at scene could have transported.
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Faslifability
- The ability of a theory to be disproved by being tested
- against know information
Seek to disprove a theory
Look @ pleasurable alternatives
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1. formulate a question
2.father measurable observational empirical data
3.formulate a hypothesis
4.test hypothesis through experimentation
5.interpret data derived from experimentation
6.draw conclusion
7.retest if necessary
Scientific method
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trajectory
- analyze bullet holes to determine path of the bullet and
- determine position of victim and shooter
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trajectory
the path of the bullet
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ballistics
the study of a projectile in motion
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external ballistics
the bullet behavior after exciting the weapon
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internal ballistics
inside the gun
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passive
bloodstain created without any significant outside force
(ex. Cut, dripp. Or blood on hand touch wall)
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blood stain pattern analysis
the scientific study of the size, shape, location and distribution of bloodstains in order to establish the physical events that gave rise to their origin
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information that can obtained from BPA
- origin of a bloodstain
- location or position of victim at time of bloodshed. position of suspect. movement of bleeding individuals sequence of events corroboration of witness/victim
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harder nonporous
result in less spatter circular stairs at 90 degrees
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rough surfaces
result in irregular shaped stains
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Tail points to direction blood is traveling
1
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passive
- bloodstain created without any significant outside force
- (ex. cut, dripp or blood on hand touch wall)
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spatter
- exhibit directionality vary in size are associated with sourse of blood being subjected to an extreme force .
- (ex. steping in blood)(gunshot)
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altered
indicated the blood or pattern that has undergone a physical alternation
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spatter"projection mechanism, cast off pattern
a pattern usually liner in configuration when blood is released or flung from an object in motion
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arterial
- blood exiting the body under pressure from a breached artery.
- many exhibit fluctuations EKG
- intense red colo; oxygenated
- downward flow pattern
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expirated
blood that has been blown by the nose, mouth, or a wound in the respiratory system. often are diluted from salvia or mucus.
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area of convergence
- 2D point from which the stains originated.
- pick around 8-12 stains
- use strings or draw lines down axis of stain.
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area of origin
3D point from where the stain was projected
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exempler
an authentic sample used for comparison purposes
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