Processing the Crime Scene
CSP
What does it involve?
• the sequence of events by which all evidence at a scene is located, recorded
and collected
Exercise 3.1
• size of scene
• number of pieces of evidence
• number of CS officers (importance of case)
• difficulty in finding evidence
• difficulty in collecting evidence
Steps involved
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initial photography
sketching the scene
searching for evidence
documenting the location of evidence
collecting and preserving evidence
Sketching the crime scene
• must be done at the scene
• does not have to be beautiful or perfect
• representation of the basic layout of the important aspects of the scene
Exercise 3.2
• shape and dimensions of crime scene
• location of fixed items within scene
• location of evidence
• draw the basic outline and mark important measurements
• the main sketch will be a floor/ground plan: bird’s eye view
• add fixed scene items:
• indoor: doors, windows, furniture
• outdoor: roads, creeks, buildings
• add evidence (use letters for small items)
• features above ground/floor level will need a separate sketch (elevation
view)
• locate small items on the sketch by triangulation
1200
Exercise 3.3
• 3.2 – shape, furniture
• 3.3 - roads
A
875
Searching
Give examples of physical evidence that is:
(a) hidden
• something inside a drawer, box, underwater
(b) very small
• hair, fibre
(c) invisible
• smell, vapour
Give examples of non-physical evidence that can be observed during the search
of a crime scene?
• doors open/closed, lights on/off
Why are these qualities important?
Attention
• don’t miss anything
Patience
• you will have to spend a lot of time of time looking at “nothing” to find the
important items
System
• you will miss the “bits in between”
A search should not:
• disturb evidence before it is recorded, and
• contaminate or destroy evidence
Numbered markers:
• put down near the evidence
• clearly indicate its presence
• help identify that evidence in the documentation (photographic and
written)
All items are recorded on a Evidence Log:
• tag number
• item description
• person who found it (if more than one involved in the search)
• other information
Documenting a crime scene
• written notes (by hand or on computer)
• still photographs
• video
EXERCISE 3.6
What extra value in documenting the processing of the crime scene is provided
by:
(a) still photographs
• show details which are too hard to describe in words
(b) video
• provides “walk through” capability
(c) written notes
• some things can’t be photographed
Written notes
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made at the time that events occur, not afterwards
made in chronological order
detail all actions
complete and thorough
clearly and legibly written
record unexpected or negative conditions (e.g. lack of blood around victim,
no signs of forced entry, lights on/off)
• be specific
• record the relevant
• leave fine detail to photography
Types of photographs
• overall – these provide a basic overview of the layout of the scene
• unlikely that one single photo will be able to cover the entire
scene
• Ex 3-7 Why can’t one overall photo cover even a small room?
• it can’t include the wall in line with you
• evidence-establishing – these demonstrate the location of items of
evidence relative to the recognisable parts of the scene (eg walls,
furniture, trees, cars)
• use of numbered “labels” to help pinpoint evidence and link it to
log
• evidence-closeup - record the presence and appearance of the
physical evidence
• the item must fill the frame of the photo to provide maximum
detail
EXERCISE 3.8
• How would you take the closeup photo for the evidence in Figure 3.5 so that
the scale is evident?
• someone else needs to hold the scale near the blood spatter
• don’t stick it to the box
• EXERCISE 3.9
• Assume you are required to photograph a house that has been burgled.
What photographs of each type should you take?
• Overall:
• exterior of house showing point of entry
• any rooms where evidence is expected
• Establishing – showing location of evidence
• Closeup – each piece of evidence
Collection and preservation of evidence
• done after the scene is thoroughly documented
• most fragile or most easily lost evidence collected first
• it may be collected before the whole scene is searched and documented
if considered likely to be lost
Exercise 3.10
(a) What types of evidence are the most fragile/easily lost?
• fingerprints (and other types of prints)
• almost anything outdoors if the weather is bad
(b) What types of evidence might need to be moved?
• bodies
• dangerous substances
General rules for evidence collection
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most evidence - paper containers such as packets, envelopes, and bags
liquid items - non-breakable, leakproof containers.
arson evidence - air-tight, clean metal cans
large quantities of dry powder - plastic bags
moist or wet evidence, eg blood, plants
• temporarily in plastic containers
• back at the “office” - completely air dry
• the repackaged in a new, dry paper container
General rules for evidence collection
• any items which may cross contaminate each other must be packaged
separately
• the “containers” should be closed and secured to prevent the mixture of
evidence during transportation
• each “container” should have:
• a unique identifying code number
• the collecting person's initials
• the date and time it was collected
• a description of the contents
• the case report number
Value of evidence
• some evidence is more useful than others
• it should be dealt with first
EXERCISE 3.11
Why are fingerprints a more valuable piece of evidence than fibres, pieces of
glass etc?
• fingerprints, if good, are unique
• fibres and glass can occur in many locations
• cannot definitely link suspect to scene
EXERCISE 3.12
Give examples of items of evidence likely to have bodily fluids on them that:
• could be transported back to the lab
• clothing
• weapons
• vehicles
• could not be transported back to the lab
• fixed parts of buildings
• ground, eg grass, paving
Other collection issues
• firearms on TV shows vs reality
• double bagging of trace items – why?
• too easily lost from single packet
Presumptive tests
• identification of whether an item is actually relevant
Exercise 3.13
Why are these important?
• quick
• to be useful on site
• simple
• to be useful on site
• sensitive
• minimise amount of evidence consumed
• provide a visual result
• no extra equipment required
False positives
• few presumptive test are totally specific
• can give a positive test for materials other than the intended one
• known as a false positive
Exercise 3.14
Given false positives, what conclusion can you draw from:
• a positive test
• could be relevant evidence
• a negative test
• very unlikely to be relevant evidence
• Do you think this limitation is a problem?
• no
• better to take much back to the lab than leave real evidence behind
Latent fingerprints
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2.
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finding them
making them visible
recording or transporting them
EXERCISE 3.15
Why is contrast required for dusting powders?
• step 2 above