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Forensic Biology > Bloodstain Pattern Analysis > Flashcards

Bloodstain Pattern Analysis Flashcards

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1
Q

bloodstain pattern analysis

A

an in-depth evaluation of bloodstain pattern

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2
Q

factors to consider in bloodstain pattern analysis

A
  • size
  • shape
  • number
  • dispersion
  • volume
  • location
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3
Q

what does BPA define?

A

the nature of the action that created it

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4
Q

determinations from blood stains

A
  • height of impact
  • direction of travel
  • angle of impact
  • nature of the force
  • relative positions of individuals at a scene
  • the sequence of events may have occurred
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5
Q

Dr. Eduard Piotrowski

A
  • first known, systematic study of bloodstain pattern
  • concerning the origin, shape, direction, & distribution of the bloodstains
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6
Q

Victor Balthazard

A
  • explained Forensic Medicine importance to Congress
  • recognized empirical relationship of stain shape to angle impact
  • introduced the ‘stringing concept”
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7
Q

Herb MacDonell

A
  • published seminal studies & provided the first training
  • flight characteristics & stain patterns of human blood
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8
Q

SWGSTAIN

A

mission to promote and enhance the development of forensic bloodstain pattern analysis practices through collaboration of government forensic laboratories, law enforcement, private industry, and academia

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9
Q

what is blood affected by?

A
  • gravity
  • surface tension
  • viscosity
  • air resistance
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10
Q

what holds a blood droplet together in flight?

A

surface tension

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11
Q

gravity is consistent =

A

blood in flight in consistent

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12
Q

viscosity

A

the resistance to flow

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13
Q

what is the effect of air resistance dependent on

A

droplet size

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14
Q

the smaller the droplet …

A

the greater the force effect

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15
Q

does blood spontaneously breakup?

A

not unless it is acted upon by an external force

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16
Q

what path does blood take?

A

the path of least resistance

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17
Q

what special property does blood have?

A

an adhesive property

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18
Q

Pattern Diversity Principle

A

combination of blood volume and forces acting on those volumes results in recognizable classes of patterns

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19
Q

Principle of Stain Shape & Vector

A

the shape of the bloodstain provides indicators as to the direction of deposition & spatial origin of the blood

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20
Q

Physically Altered BPA Principle

A

exposed blood will react to environmental conditions in a predictable manner

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21
Q

what force produces a high velocity blood splatter?

A

an external force greater than 100 feet/sec

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22
Q

high velocity blood splatter stains

A
  • sometimes referred to as a mist
  • tend to be less than 1 mm
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23
Q

what creates high velocity blood splatter?

A
  • usually created by gunshots or explosives
  • may result from industrial machinery or expired air (coughing or sneezing)
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24
Q

high velocity blood splatter travels

A

travels the shortest distance because of the resistance of the air against their small mass

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25
Q

what force produces a medium velocity blood splatter

A

an external force between 5 feet/sec and 25 feet/sec

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26
Q

medium velocity blood splatter stains

A

generally measure 1 to 3 mm

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27
Q

what creates medium velocity blood splatter?

A
  • blood flying from a body to a surface as a result of blunt or sharp force trauma
  • body colliding with rounded or edged surfaces/vehicles
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28
Q

what creates a low velocity blood splatter?

A

an external force less than 5 feet/sec (normal gravity)

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29
Q

low velocity blood splatter stains

A

generally 3 mm and larger

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30
Q

what causes a low velocity blood splatter?

A
  • blood dripping from a person walking or running
  • bloody weapon
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31
Q

low velocity blood splatter drips

A

dripping blood often falls at a 90° angle & forms a 360° (circular) stain when it hits a flat surface

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32
Q

3 types of bloodstains

A
  • passive
  • splatter
  • altered
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33
Q

example of passive bloodstains

A

gravity

34
Q

example of spatter bloodstains

A

energy applied creating flight

35
Q

example of altered bloodstains

A

physically/environmentally altered

36
Q

passive blood stains

A
  • drop(s)
  • flow
  • large volume
37
Q

spatter bloodstains

A
  • impact mechanism
  • secondary mechanism
  • projection mechanism
38
Q

secondary mechanism

A

spines & satellite stains

39
Q

satellite stains

A

smaller bloodstain originating from a larger blood stain

40
Q

altered bloodstains

A
  • time lapse
  • diluted
  • diffused
  • insects
  • contact
  • voids
41
Q

wipe

A

moving through a pre-exisiting blood stain

42
Q

swipe

A

transfer from a blood bearing surface

43
Q

the basic premise of BPA theory

A

based on stain size, shape, volume, orientation, & other physical characteristics, the analyst can differentiate between basic types of blood shed events

44
Q

what must an analyst do to support any claim about a pattern?

A

must be able to articulate what characteristic led him to his decision

45
Q

BPA scientific process/method

A
  • data collection/gather case information
  • segregate patterns, then categorize the patterns
  • documentation, notes of sizes, shapes, directionality, areas or origin, etc
  • evaluate different hypotheses
  • test different theories
  • conclusions/results, supported by physical evidence
  • peer reviewed
46
Q

area of convergence

A

the area containing the intersections generated by lines drawn though the long axes of individual stains (2D)

47
Q

a longer blood stain is formed by

A

a lower angle of impact

48
Q

what increases spatter diameter?

A

height

49
Q

when do spines appear at the edge of a stain?

A

when blood drops come from greater heights

50
Q

direction of tail =

A

direction of blood

51
Q

equation: angle of impact

A

sin theta = width / length

52
Q

determining the area of origin

A
  • 3D location from which spatter originated
  • using the stringing method
53
Q

presumptive test

A
  • indicates possible presence of a substance
  • “this is likely saliva”
54
Q

confirmatory test

A
  • conclusively identify a substance
  • “this is definitely human saliva”
55
Q

pros of presumptive test

A
  • narrow possibilities & helps to decide which test to do next
  • can use on large areas
  • can locate evidence not visible with the naked eye
  • cost effective
  • portable
  • sensitive
56
Q

cons of presumptive test

A

many false positives

57
Q

pros of confirmatory test

A
  • conclusively identify a substance
  • wont waste money when moving on to DNA testing
  • MUCH smaller risk of false positives
58
Q

cons of confirmatory test

A
  • higher cost
  • require additional equipment
  • takes longer
59
Q

screening for bodily fluids - when not readily apparent

A
  • many body fluids fluoresce under a black light
  • things that fluoresce contain phosphors
60
Q

body fluids that fluoresce

A
  • urine
  • saliva
  • sweat
  • semen
61
Q

phosphors

A

substance that absorbs energy outside of the visible spectrum & re-emits the energy as visible light

62
Q

blood under a black light

A
  • does not fluoresce
  • it sometimes appears darker
63
Q

Human Blood Presumptive tests

A
  • Kastle Meyer Test
  • Luminol
  • Alternate Light Source
64
Q

Human Blood Confirmatory tests

A
  • Precipitin test
  • Hematrace
  • does not confirm DNA presence
65
Q

quality control

A

are the tests running properly?

66
Q

quality assurance

A

does the whole program work?

67
Q

negative control

A

not expected to produce results

68
Q

positive control

A

expected to produce results

69
Q

what should be a positive control?

A

where blood is present

70
Q

what should be a negative control?

A

where blood isn’t present

71
Q

Presumptive Blood Tests (Luminol & Phenolphthalien)

A
  • uses hemoglobin to catalyze the oxidation of certain reagents
  • hydrogen peroxide often used as oxidizing agent
  • visible as a color change
72
Q

Confirmatory Human Blood Test

A
  • Precipitin Test
  • ABAcard Hematrace
73
Q

ABAcard Hematrace

A
  • remove a piece of fabric/swab with suspected blood
  • add to provided vial (containing buffer) & shake
  • remove liquid from vial & put two drops in the same wells
74
Q

Human Semen Presumptive Tests

A
  • Acid Phosphatase
  • Prostate Specific Antigen
75
Q

Human Semen Confirmatory Tests

A
  • look under a microscope for morphology and stains
  • look for christmas tree in sperm
76
Q

Acid Phosphatase Test

A
  • presumptive test
  • semen will produce a positive color change in < 1 minute
  • affected by concentration & age of stain
77
Q

presumptive & confirmatory tests - Saliva

A

based on the presence of saliva alpha amylase

78
Q

Saliva Presumptive Test

A

Phadabas

79
Q

Saliva Confirmatory Test

A

RSID (Rapid Stain Identification) Test

80
Q

neutralization test

A

if AB antigens are present in the fluid they will react with (neutralize) antibodies, so that they don’t interact & agglutinate red blood cells with the same antigen

81
Q

saliva + antibody A + A Type RBC = no agglutination

A

saliva from a secretor of A saliva

82
Q

saliva + antibody A + A Type T RBC = agglutination

A

saliva from a non-secretor or saliva from a secretor without A type RBC

Forensic Biology (17 decks)

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