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Intro To Forensics > Bloodstains > Flashcards

Bloodstains Flashcards

1
Q

Very large blood drops form a _____ shape

A

Hamburger bun

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2
Q

Most blood drops form a ___ as they move through the air

A

Nearly perfect sphere

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3
Q

Contact/Collapse

A

Droplet makes initial contact with the surface and collapses from the bottom up

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4
Q

Displacement

A

Blood droplet’s energy is directed outwards, causing blood to collect into a disc-like rim

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5
Q

Dispersion

A

Motion of the rim is redirected upwards; spines formed during prior step extend further outwards

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6
Q

Retraction

A

Surface tension pulls the stain back flat into the substrate

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7
Q

Rules to keep in mind when measuring bloodstains:

A

-Measure only the main body of the bloodstain
-Choose a point in the stain that naturally completes the ellipse or circle

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8
Q

The place where there is the most blood is typically…

A

The end of the incident

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9
Q

Satellite Stains

A

Smaller bloodstains that originated from a parent stain

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10
Q

Spines

A

Long lines coming from circular portion of a stain

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11
Q

Tails

A

Small circles on a spine(?)

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12
Q

Defined as the force that pulls the surface molecules of a liquid toward its interior, decreasing the surface area and causing the liquid to resist penetration?

A

Surface Tension

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13
Q

What is the name for patterns that display an absence of bloodstains in otherwise continuous patterns of staining?

A

Void Patterns

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14
Q

What general category of stains includes transfer, flow patterns, saturation stains, and stains from dripping blood?

A

Passive

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15
Q

A stain is approximately twice as long as it is wide. What can we say about the angle of impact?

A

It was close to 30°

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16
Q

The terms low, medium, and high velocity impact patterns have been replaced by SWGSTAIN with the term…

A

Impact Stains

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17
Q

Blood will not break into smaller droplets or spatters unless what is disrupted?

A

Surface Tension

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18
Q

What type of target surface a drop of blood strikes will create little if any spatter?

A

Smooth ceramic tile

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19
Q

Bloodstain vs bloodstain pattern

A

Bloodstains are one deposit of blood on a surface, patterns are multiple

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20
Q

How much blood is present in humans?

A

4-6 liters

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21
Q

Blood is composed of…

A

Hematocrit & Plasma

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22
Q

Surface tensions pulls blood ____ until ____

A

Into a sphere; acted upon

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23
Q

Under surface tension, liquid behaves as….

A

An elastic

24
Q

Drip

A

Blood that falls under gravity ONLY

25
Q

Satellite spatter

A

Produced from the main drip

26
Q

The ____ of the bloodstains increase as the height ___

A

Diameter; increases

27
Q

Impact spatter

A

Object striking liquid blood
-Drops move outwards around the parent stain in directions of force

28
Q

Cast-off pattern

A

Blood is released or thrown from a blood-bearing object in motion
-Roughly linear/curved
-Shape changes from round to elongated

29
Q

Cast off appearance depends on

A

Location and shape of target
Speed of the swing
Size of the object
Number of swings

30
Q

Projected pattern

A

Blood exiting the body under pressure
-Very high volume
-Very bright red

31
Q

Expirated blood

A

Blown out of an orifice (nose, mouth)
Often diluted & presence of mucus

32
Q

Area of convergence depicts a ____

A

2D point of impact

33
Q

The area of convergence is found ______

A

Where lines intersect along the axis of the stain

34
Q

Area of origin

A

Intersection of angles in 3D

35
Q

How do we find the area of origin?

A

Find the AOC
Find angle of impact for each stain
Converge the angles

36
Q

Accompanying Drop

A

A small blood drop produced as a by-product of drop formation

37
Q

Altered Stain

A

A bloodstain with characteristics that indicate a physical change has occurred

38
Q

Angle of Impact

A

The acute angle (alpha), relative to the plane of a target, at which a blood drop strikes the target

39
Q

Bubble ring

A

An outline within a bloodstain resulting from air in the blood

40
Q

Cessation Pattern

A

A bloodstain pattern resulting from blood drops released from an object due to its abrupt
deceleration

41
Q

Flow Pattern

A

A bloodstain pattern resulting from the movement of a volume of blood on a surface due to
gravity or movement of the target

42
Q

Perimeter Stain

A

An altered bloodstain which consists of its edge characteristics, the central area having been partially or entirely removed

43
Q

Saturation Stain

A

A bloodstain resulting from the accumulation of liquid blood in an absorbent material

44
Q

Serum Stain

A

The stain resulting from the liquid portion of blood (serum) that separates during coagulation

45
Q

Splash Pattern

A

A bloodstain pattern created from a large volume of liquid blood falling onto a surface.

46
Q

Swipe Pattern

A

transfer of blood from a moving “dirty” source onto another one

47
Q

Features of an impact spatter

A

Fan-like pattern with a variety of sizes, larger stains towards one focus; all blood patterns together in one region

48
Q

The “tail” of a bloodstain pattern points in the….

A

Direction of travel

(Away from the source)

49
Q

Which stains can you determine area of origin for?

A

Impact
Forward
Back
Sometimes cast-off

50
Q

Back spatter

A

Blood that comes back towards the point of origin

51
Q

Forward spatter

A

Blood that travels with the direction of travel

52
Q

Relation between saturation stains and transfer stains

A

Saturations stains can obscure or create transfer stains if still wet

53
Q

Transfer stain

A

Contact between blood bearing surface and another surface

54
Q

Wipe pattern

A

An object moves through an existing stains
We usually can see remnants of original stain shape

55
Q

What are some criticisms of bloodstain analysis?

A

Highly subjective
Limited testing of basic science
Limited education requirements

56
Q

The area of origin is ____ oriented in a _____ line ____ from the area of ______

A

always; straight; 90 degrees; convergence

57
Q

Formula for determining the angle of impact

A

sin^-1 times width, divided by length

Intro To Forensics (19 decks)

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