Lecture 4 - Introduction to Bloodstain Pattern Analysis (BPA) Flashcards

Question 1

Q

BPA is the study of

Answer

A

the shapes, sizes and locations of bloodstains in association with knowledge of the underpinning sciences (physics, mathematics and biology) to provide information on the event or a sequence of events that resulted in the deposition of these bloodstains or bloodstain patterns.

the interpretation of bloodstain pattern present at violent crime to help reconstruct the events that occurred during the commission of a crime

Question 2

Q

How physics comes into play with BPA

Answer

A

Look at physical characteristics, look at how blood behaves specifically since it is a liquid know that they have surface tension and viscosity so they follow the laws of physics and if a external force is applied to them then they act based on the laws of physics
Laws of physics are reproducible and reliable

Question 3

Q

BPA may provide valuable information about …

Answer

A

WHAT occurred during the course of the crime and the order in which these events took place.

Question 4

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Recording of BPA

Answer

A

It is essential that all bloodstains present at a crime scene are recorded by an appropriate combination of notes, sketches, photographs and/or video footage before they are disturbed by the investigators

Question 5

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Bloodstain interpretation …

Answer

A

Interpretation of bloodstain patterns can be undertaken in various locations:
at a scene (indoor, outdoor, vehicle, on a body), - Most BPA occurs at the crime scene

in the laboratory (e.g. clothing, footwear, weapons) - Items that can be removed from scene can be taken to laboratory - lab examination is more in depth/detailed, more equipment, better lighting and time in the laboratory environment
The items usually looked at in the lab are the weapons, clothing, footwear

from photographs
Dependent on the quality
Depends on whether the analyst can interpret the images
This is an area of forensic analysis that is likely to improve and become more prominent with the constant improvements in technology

Question 6

Q

Using the rules of physics, bloodstain pattern evidence can determine …

Answer

A

Area of origin(s) of blood

Distance between target surface and origin of blood

Type and direction of impact that produced bloodstains
Can look at the trajectories of the bloodstains

How many blows/shots (or a minimum number)

Position of bleeder during bloodshed

Movement of bleeder
Can trace the movement of the bleeder - whether they were dragged, walked away, ran etc

Sequencing, when different stains are deposited
If there are multiple patterns you can sometimes figure out which patterns came first

Obtain pertinent stains for further analysis (DNA)
Takes time and expensive to taxpayers, need to determine the best patterns to analyse for the most efficient and effective use of equipment

Question 7

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DNA analysis answers the question -

Answer

A

WHO?

The improvements of DNA analysis has really changed the landscape for forensic scientists

Question 8

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BPA helps answers the question -

Answer

A

WHAT?

‘what happened’ is usually in contention rather than who, this is why blood pattern analysis is important because it can help piece together the series of events that took place

Question 9

Q

Bloodstain pattern analysis can be of great use in many forensic scenarios, for example:

Answer

A

Determining the cause of an unexplained death (homicide/suicide/accidental)

Body is at ‘odds’ with scene
Blood stain patterns may indicate the body has been moved from the original position where the blood had been deposited

Assessing claims by witnesses and accused
See if there is support for a particular story or not

Defence of suspect is ‘self defence’ or ‘helpful bystander’

Two or more persons have bled at scene
BPA can be useful to determine the main bleeder
Might be able to identify blood from the offender which is really important

Multiple blood patterns observed

Question 10

Q

Bloodstain =

Answer

A

any deposition of blood on a surface

Question 11

Q

blood stains often occur in groups =

Answer

A

bloodstain pattern

Pattern usually indicates that these bloodstains have come from the same event e.g. same blow

Question 12

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Terminology determined now by …

Answer

A

In 2017 these were updated by the OSAC Bloodstain Pattern Analysis subcommittee

Question 13

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8 scientific method steps for BPA

Answer

A

These 8 steps are very important and outline the scientific method
BPA is quire objective and scientific

Scene/item overview
Locating blood
Documentation/record observations
Step 3 is about collecting the data
Recording and measuring
Analysis of elliptical stains
Mathematical analysis
Placing stains into groups
Use the analysis to do this
Classification and Interpretation
Formulate hypothesis and theories
Form conclusions

Question 14

Q

Step 1 - scene/item overview

Answer

A

Define boundaries of examination
How big is the job? - determine the resources and manpower required
Make sure the expectations for the scene are communicated properly

Document conditions
Memory unreliable, so notes are very important - can give evidence much later in time such as years in the future so having a record of important details is essential

Limit contextual information to minimise biasing effects
Go in with an open mind when doing scene examination

Question 15

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Step 2 - Locating

Answer

A

Search and identify visual stains
Visually identify and then can do chemical tests for blood thats hard to

Use presumptive chemical tests for confirmation

Low power stereo microscope
Helpful for very small traces of blood such as blood caught in shoe tracks or in a watch strap

Search for non visible blood with enhancements
NIR (near infared) camera - Useful dark coloured objects where blood is believed to be where you can’t see contrast, Non-destructive so useful however its effectiveness is dependent on the dyes in the fabric 
Chemical enhancements (eg luminol) - These cause a chemical reaction (usually a colour change)

Question 16

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Luminol examination

Answer

A

A chemical reagent which reacts with traces levels of blood to produce a chemiluminescent reaction.
Spray reagent onto the surface
Chemical reaction so it is destructive and it reacts with traces levels of blood if present after being sprayed onto the surface of interest
Light is emitted if blood is present therefore the testing has to be done in the dark

The reaction must be viewed in the dark making documentation difficult.
Have trained photographers so that documentation can still occur

Very sensitive but the least specific chemical test for blood. False positives can occur

Training and experience are required to interpret the results.

Question 17

Q

Luminol can be used at scenes where blood is suspected to be present and:

Answer

A

Trace (non-visible) levels are anticipated

Clean up of blood is suspected

Movement of body/objects e.g. dragging of body

Patterns may be present e.g. footwear, footmarks

Note - Luminol works better on more oxidised stains

Question 18

Q

Step 3 - recording observations

Answer

A

The number of bloodstains - Could be a few, hundreds or thousands
Location
Size
Shape (including directionality) - Shape can tell us the direction that the droplet was travelling when it landed
Colour and intensity of blood within stain - Could be one colour, could be darker in some areas and lighter in others dues to the deposition of blood
Spatial relationship between bloodstains
Spatial relationship between bloodstains and other objects or surfaces nearby
Alteration/disturbance of different stains
The surface characteristics of the material (target) upon which stains are deposited- Is the surface absorbent? Soft? Smooth? - influences how the blood behaves when it lands and therefore how the stain looks

Question 19

Q

Step 4 - Analysis of elliptical stains

Answer

A

variation in shape with impact angle … As the angle decreases (from 90 towards oblique) the length increases —> stains become more elliptical = W:L ratio decreases—> when you graph this you can find out the predicted path trajectory (which follows the sine law)

area of origin determination

Question 20

Q

Elliptical stains are the result of …

Answer

A

small droplets of blood that land on a surface, they spread as they land and collapse, if they land straight down then they will spread evenly to a circle but if it lands on an angle then it forms an elliptical shape

Question 21

Q

Direction of elliptical stains

Answer

A

Nose’ of the stain indicates the direction of the stain

As the droplet collapses, the direction that the droplet is travelling can sometimes force a wave cast off to lift up off the main stain and then form this spine or tail (really should be called a nose because it is coming off the front) and it points to the direction that the blood is travelling

These spines are really useful for determining direction of the stains

Question 22

Q

Angle of landing of the blood stain and its effect on the elliptical shape

Answer

A

The ellipses have a width and a length, and this can change
At 10 degrees it is a very long and thin stain
At 60 degrees the blood stain is more circular

Question 23

Q

Elliptical stains - variation in shape with impact angle

Answer

A

As the angle decreases (from 90 towards oblique) the length increases —> stains become more elliptical = W:L ratio decreases—> when you graph this you can find out the predicted path trajectory (which follows the sine law)

Question 24

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Elliptical stains - area of origin determination

Answer

A

Combining the directionality of selected stains with their angle of impact, the straight line trajectory can be estimated

Question 25

Q

Step 5 - Placing stains in group

Answer

A

Identify evidence of an association between the stains (common characteristics):
Same location
Similar size/size range
Shape of stains (including directionality)
Originate from common area (share 2D or 3D convergence)
Overall shape/distribution of stains (radial, linear, curvilinear)

Question 26

Q

Step 6 - classification of bloodstain patterns

Answer

A

There are 3 primary classification groups for bloodstain patterns:
(These classification are based on the mechanisms of how the bloodstains were created)
1) Passive Stains (caused by gravity)
Caused by gravity and bleeding alone

2) Spatter Stains (caused by an external force)
Extra force is applied to liquid blood which has caused it to form little droplets which then go on to form circle and elliptical stains

3) Transfer Stains (caused by contact)
You have blood on an object and it makes contact with another surface which causes it to create a transfer stain

Question 27

Q

3 classifications of blood stain patterns

Answer

A

passive stains
spatter stains
transfer stains

Question 28

Q

passive stains caused by

Answer

A

gravity

caused by gravity and bleeding alone

Question 29

Q

spatter stains caused by

Answer

A

an external force

Extra force is applied to liquid blood which has caused it to form little droplets which then go on to form circle and elliptical stains

Question 30

Q

transfer stains caused by

Answer

A

contact

You have blood on an object and it makes contact with another surface which causes it to create a transfer stain

Question 31

Q

active stain

Answer

A

Active bloodstains are defined as those caused by blood that may have been made to travel by a force other than that of gravity such as impact to the body of a victim by a fist and/or weapon OR protection of pressurised blood onto a surface

i.e. active stains are spatter stains and transfer stains

Question 32

Q

characteristic feature of projected pattern

Answer

A

projection of pressurised blood onto a surface (volume of blood issuing from a punctured artery under pressure may be large (known as gushes) or relatively small (termed spurts) and the overall pattern of these projected bloodstains may clearly reflect the rise and fall of blood pressure in the arteries and the present of spines (i.e. linear stains) is also characteristic of this type of active bloodstain and is caused by the volume of blood involved and the pressure under which the blood is projected)

Question 33

Q

characteristic feature of cast off pattern

Answer

A

one that emanates from a secondary objects that is soaked with blood such as the weapons used in an attacking blood may be flung off the object as it is moving or as a result of a sudden cessation in its motion, stains created in this fashion are sometimes referred to as cast off stains (the cast off pattern produced is characteristically composed of individual drops of blood distributed along a line. This line may be curved or straight depending on the circumstance of its deposition. By examining such bloodstain patterns, it may be possible to deduce the minimum number of times that a victim has been struck, as each line corresponds to at least one strike.

Question 34

Q

direction of travel may be discerned from the direction in which tails of the individual stains point (this is usually the same as the direction of travel of the blood droplets) … EXCEPTION =

Answer

A

stains created when a larger droplet of blood impacts on a surface therefore throwing off smaller droplets. The tail of these smaller, ‘satellite’ stains point towards the parent drop. It is therefore important to distinguish between parent and satellite stains when interpreting the direction of travel

Question 35

Q

As the angle of impact decreases,

Answer

A

as the angle of impact decreases, the shape of the resultant bloodstain becomes progressively more elongated.

Question 36

Q

Secondary classifications of passive blood stains list

Answer

A

Drip stains
drip pattern
flows/flow pattern
saturated, pooling stain

Question 37

Q

Secondary classifications of passive blood stains - drip stains

Answer

A

A bloodstain resulting from a falling drop that formed due to gravity.

Typically result from a bleeding injury or blood falling from an object with lots of blood on it

Target can result in different presentation of the bloodstain e.g. on the corrugated cardboard is quite a non-porous surface so the blood will spread over it and spread out to cause a large stain but it is also rough so it causes splashing when the blood droplet lands and it breaks up which causes little spines and satellite stains around the outside vs on the carpet the blood falls into the 3D matrix and is absorbed into the material and blood splattering is limited/stopped from spreading with dampens the splashing as well

Passive bloodstains: Drip trail
A bloodstain pattern resulting from the movement of a source of drip stains between two points.
A trails of drip stains might all be related to the same event and just look different because of a change in surfaces throughout the trail

Directionality may sometimes be established from the stain shape and edge characteristics

Drip stains with movement of source or target, can determine speed of source or target
Walking faster gives more prominent spines

Question 38

Q

Secondary classifications of passive blood stains - drip pattern

Answer

A

A bloodstain pattern resulting from a liquid that dripped into another liquid, at least one of which was blood.
When blood is dripped and drips onto older stains to create a pattern since the different stains start to overlap
Usually blood into blood, but could be blood into another liquid on a surface or water etc dripping into blood on a surface
Can dilute the amount of blood if it is a liquid other than blood dripping onto the bloodstain
Central stain and then small satellite stains from the splashing effect

Question 39

Q

Secondary classifications of passive blood stains -flows/flow pattern

Answer

A

A bloodstain pattern resulting from the movement of a volume of blood on a surface due to gravity or movement of the target
When blood deposits on a surface and the adhesive forces on that surface mean that the blood cannot hold there so flows in the direction of gravity instead creating a flow pattern
Useful for sequencing object positioning e.g. with the bloodstain on the heater, if it was found lying on its side then a forensic scientist would be able to say that the heater was upright when the bloodstain was deposited because of the flow of gravity

Question 40

Q

Secondary classifications of passive blood stains -saturated, pooling stain

Answer

A

Saturation stain - A bloodstain resulting from the accumulation of liquid blood in an absorbent material.
Pooling stain = on a non-absorbent surface such as Lino flooring

Indicates that the person has been in this position for a reasonable amount of time since there is a large amount of blood in the same area –> May help to reveal information about the length of time that has passed since the blood shed occurred, this is because drying times may be estimated

Question 41

Q

Passive bloodstains - drip trail

Answer

A

Passive bloodstains: Drip trail
A bloodstain pattern resulting from the movement of a source of drip stains between two points.
A trails of drip stains might all be related to the same event and just look different because of a change in surfaces throughout the trail

Directionality may sometimes be established from the stain shape and edge characteristics

Question 42

Q

Secondary classifications of spattered stains list

Answer

A

impact 
expiration 
arterial pressure 
Cast off 
firearms

Question 43

Q

Secondary classifications of spattered stains - impact

Answer

A

A bloodstain pattern resulting from an object striking liquid blood.
Stationary source of blood being hit and then the blood spreads out from here
Can have larger stains because of overlapping of blood stains due to the impact creating similar flight paths for the blood
Blood is incompressible which means that when it is struck it cannot get smaller and it has to go somewhere
Not an instantaneous process of blood stain making, it is a dynamic process because the none of the forces are in equilibrium
Can have a radial distribution due to the drag and having droplets flying through the air which slows them down

Question 44

Q

spatter stains in more depth

Answer

A

Spatter Stains (caused by an external force) = bloodstain resulting from a blood drop dispersed through the air due to an external force applied to a source of liquid blood. Spatter stains are typically small and elliptical/circular in shape.
Spatter stains are formed from droplets of blood in flight
Created in response to a force applied to the blood
Resulting pattern is dominated by small circular and elliptical stains

Question 45

Q

Secondary classifications of spattered stains - expiration

Answer

A

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound.
e.g. coughed blood (not very diluted, large volume of blood in mouth and coughed out hence its consistent colouring unlike other airway blood stain patterns)
Anything to do with force from the airways
Often diluted if comes out airways i.e. nose and mouth, usually indicated by a darker outline around the blood stain (coffee rim effect***)
Expirated blood is complicated and varied

Question 46

Q

Secondary classifications of spattered stains - arterial pressure

Answer

A

( a projected bloodstain pattern, similar to hydraulic pressure that causes blood to be spattered)
A type of projected spattered bloodstain: A bloodstain pattern resulting from the ejection of a volume of blood under pressure. e.g arterial breach

High pressure causing the blood to be splattered
Often get serpentine arcs for the trajectory because of the way the heart beats and the changing blood pressure of the blood during a heart beat
The droplets are often quite large anyway but as they break up along the line of blood they start going on top of each other and cause flow patterns which is quire characteristic

Question 47

Q

Secondary classifications of spattered stains - cast off

Answer

A

A bloodstain pattern resulting from blood drops released from an object due to its change in motion.
Centripetal force is at play in these types of bloodstains
The faster you swing, the more blood that will come off (therefore a larger amount of blood on the blood stains will be seen)
Usually from crimes when someone is using an object to beat someone
Result of either an object being flung or an object stopping suddenly in motion and the blood is released from the object
Cast off - left to right directionality, following an object’s swing
Cast off and impact patterns are often found together because beating someone (causing impact to their body) usually involves an object or their fist which needs to be swung to cause the most damage therefore causes flinging of the blood and creates a cast off blood stain pattern

Question 48

Q

Secondary classifications of spattered stains - firearms

Answer

A

Own category because although it could be classified as impact, the gases in firearms can expand and impact the blood by atomising the blood

Question 49

Q

Secondary classifications of transfer stains list

Answer

A

pattern transfer
wipes
swipes

Question 50

Q

Secondary classifications of transfer stains - pattern transfer

Answer

A

A recognisable mirror image or at least a recognisable portion of the original surface may be transferred to the second surface.

Mostly hands, fingerprints and footprint marks
Sometimes there can even be enough detail to do analysis of these surfaces

Question 51

Q

Secondary classifications of transfer stains - wipes

Answer

A

An altered bloodstain pattern resulting from an object moving through a pre-existing wet bloodstain.
Already have blood on a surface and something clean comes through the blood and changes it
The key here is that the blood circumferences skeletonise and there are characteristic drags of the wet blood from the centre of the stains

Question 52

Q

Secondary classifications of transfer stains - swipes

Answer

A

Bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces.
e.g. bloody hand to light switch, bloody hand to handrail
Opposite of wipe

Question 53

Q

Swipe =

Answer

A

transfer stain secondary classification

Question 54

Q

Wipe =

Answer

A

transfer stain secondary classification

Question 55

Q

pattern transfer =

Answer

A

transfer stain secondary classification

Question 56

Q

impact =

Answer

A