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Forensics > Bloodsplatter Pattern Analysis > Flashcards

Bloodsplatter Pattern Analysis Flashcards

1
Q

What are the 5 factors that affect the appearance of a bloodstain?

A
  1. The velocity at which it was travelling
  2. Distance travelled
  3. The amount of blood
  4. The angle of impact
  5. Type of target onto which it lands
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2
Q

What are the 9 things that a bloodstain can tell us?

A
  1. Number of blows struck during an accident
  2. Number of perpetrators
  3. Sequencing of events
  4. Positioning of persons within a scene
  5. Directionality of droplets
  6. Angle of impact
  7. Objects used (weapons)
  8. Force involved in the bloodshed and the direction the force was applied
  9. Evidence of clean up
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3
Q

What is bloodstain pattern analysis?

A
  • examination of the size, shape and distribution of bloodstains and bloodstain patterns
  • draws on the scientific principles of biology, chemistry, mathematics and physics
  • based on the premise that all bloodstain patterns are characteristics of the forces that created them
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4
Q

What shape will a blood droplet take in the air?

A

Sphere

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5
Q

What is a bloodstain?

A

The transfer of when liquid comes into contact wth a surface or when a moist or wet surface comes into contact with dried blood

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6
Q

What are some locations of bloodstains?

A
  • scene
  • victim (body/clothing)
  • offender (body/clothing)
  • weapon
  • vehicle
  • furniture
  • “clean up”: under rugs, linoleum, seat cushions
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7
Q

What is blood comprised of?

A
  • 55% plasma: 91% water, 8% proteins, 1% organic acids/salts

- 45% proteins: 99% RBCs, 1% WBCs, 1% platelets

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8
Q

What are the functions of blood?

A
  • transport
  • protection
  • regulation
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9
Q

How much of the body weight does blood account for?

A

8%

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10
Q

How much blood do males and females have?

A

Males: 5-6L
Females: 4-5L

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11
Q

How much blood loss will render someone unconscious?

A

1.5L

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12
Q

How much blood loss will result in death?

A

40%

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13
Q

What are the presumptive tests for identifying blood?

A
  • hemastix
  • luminol test
  • phenolphthalein test
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14
Q

What are the confirmatory blood tests?

A
  • ABA card hematrace
  • Takayama test
  • RSID test for human blood
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15
Q

Where is DNA present in blood?

A

Only in WBCs because RBCs lack nuclei and ribosomes

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16
Q

Hemastix test

A
  • presumptive test
  • looks for peroxide-like activity of haemoglobin in RBCs
  • will not detect the difference between animal and human blood
  • false positives: beetroot, rust, horseradish, copper, cabbage, animal saliva, past expiry date
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17
Q

Luminol test

A
  • presumptive test
  • luminol reacts with haematin and produces a luminescence
  • false positives have been observed with the presence of copper salts (on locks, door handles)
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18
Q

Phenolphthalein test

A
  • presumptive test
  • presence of blood detected based upon a peroxidase reaction of haemoglobin which produces a pink colour
  • false positives: saliva, pus, malt extract, vegetable extracts, the salts of certain heavy metals
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19
Q

ABA card hematrace

A
  • confirmatory test
  • immunochromatographic test for detecting the presence of human haemoglobin
  • intended for use on stains that have tested positive using the phenolphthalein test
20
Q

Takayama test

A
  • confirmatory test
  • hemochromogen crystals form when mixed with blood
  • crystals are observable under a microscope and look like salmon-pink rhomboid crystals
21
Q

RSID test for human blood

A
  • confirmatory test

- specialised antibodies detect the presence of human Glycophorin A found in RBC membranes

22
Q

What are the 4 broad categories of blood stains?

A
  1. Passive
  2. Transferred
  3. Projected
  4. Altered
23
Q

What is a satellite stain?

A

A small stain that originated during the formation of the parent stain as a result of blood impacting a surface

24
Q

The more ……. the angle of impact, the …….. elongated the teardrop

A

Accute, more

25
Q

What do passive bloodstains include?

A
  • flows, drops and pools

- usually results from gravity

26
Q

Flows

A

Accumulation of a volume of blood with regular margins that has been moved across a surfaces as a result of gravity or the countour of the surface

27
Q

Drops

A

Result in distinctive patterns diagnostic of the event.

28
Q

Pools

A

An irregular stain caused by deposition;contact by a large source of liquid blood

29
Q

When a drop strikes a surface perpendicular, the drop will be……

A

Circular

30
Q

What are the types of transfer bloodstains?

A
  • swipes, wipes and transfers

- results from objects coming in contact with existing bloodstains

31
Q

How are bloodstains documented?

A
  1. Written report: directionality and bloodstain classification
  2. Photography: photos of the scene before anything is touched or moved
  3. SketcheS and diagrams: position of the body in relation to fixed and significant objects in the scene
32
Q

Swipe

A

Pattern resulting from the transfer of blood from a blood-bearing surface onto another surface

33
Q

Wipe

A

Pattern resulting from an object moving through a preesistono wet bloodstain

34
Q

Transfer

A

A contact bloodstain created when a wet, bloody surface contacts a second surface as a result of compression or lateral movement. A recognisable mirror image (or portion) or the original surface may be transferred on to the second surface

35
Q

What does the projected category contain?

A
  • impacted, expirated, cast off and arterial
36
Q

Impact

A

Results from blood projecting through the air and are usually seen as a splatter, but may also include gushes, splashes and arterial spurts

37
Q

Expirated

A

Blood from and internal injury mixing with air from the lungs being expelled through the nose, mouth or an injury to the airways or lungs (coughing)
Seen as a fine mist, small droplets of blood

38
Q

Cast off

A

An object swung in an arc flings blood onto nearby surfaces

39
Q

Arterial

A

The spurt of blood released when a major artery is severed, often forms an arching pattern which occurs every time the heart pumps

40
Q

What does the altered category include?

A
  • Clotted, dilute, diffuse, insects, voids and sequence

- includes any other type of bloodstain that doesn’t fit into the first 3 categories

41
Q

Clotted

A

A gelatinous mass formed by the collection of blood cells in fibrin

42
Q

Diluted

A

Whole blood subject to volume alteration due to fluid addition/mix, I.e. in a sink

43
Q

Diffuse

A

Movement of blood from and area of higher to lower concentration, I.e. material absorbing blood

44
Q

Insect

A

Bloodstain resulting from insect activity

45
Q

Voids

A

Absence of blood staining in an otherwise continuous pattern

46
Q

Sequence

A

2 or more splatter types co-mingled or time sequenced

Forensics (18 decks)

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