Lecture 3 - Forensic Science and Crime Scene Investigation Flashcards
What kind of things can you leave behind?
Hair fibre DNA Fingerprints other contaminants such as pollen foot prints
Every contact …
leaves a trace
Forensic science =
science used in the court of law
Lockard’s exchange princlple =
every contact leaves a trace
Forensic evidence can be used to
dentify an offender; link suspect to victim; link suspect to scene; reconstruct a sequence of events
Crime triangles…
Crime triangles - all three legs support physical evidence or support the victim, suspect and scene being in that place
Initial action (crime scene)
Preserve life
Make sure it is safe, this is paramount
Someone in danger comes first, they must be put in a safe environment first
Risk assessment - electrical, fire, roof collapse etc.
Consider if structure is still safe
Call for additional units- How much more man power is required?
Initial assessment (crime scene)
Preserve the scene (protect from contamination) Cordons (physical barrier), scene guard Weather protection Common approach path Zones - cold, warm and hot PPE requirements
During the initial assessment by the first officer at the scene, they must ascertain whether any of the following are present or nearby…
Injured persons
Victims
Eyewitnesses
Suspects
Initial assessment - Preserve the scene from contamination
Avoidance of any unnecessary damage to the physical evidence present at the scene, this evidence is most likely to be found at the location(s) within the scene at which the crime(s) took place and along any path taken through the scene by the perpetrator(s) and possible the victim(s)
Avoid leaving fingermarks at scene
Saving lives takes precedence over both the arrest of a suspect and the preservation of physical evidence
There are two principal potential agents of damage from which the physical evidence present must be protect, namely people’s inappropriate actions and the weather - try to isolate the physical evidence from these factors
Initial assessment - cordons (physical barrier), scene guard
In many cases the cordon/barrier is either absent or does not fully encompass the scene —> under these circumstances a barrier made of police plastic tape is usually sufficient
The cordoned area should include as wide an area a practical. Certainly, it should include the location(s) in the scene where the crime(s) took place and the points of entry to and exit from the scene of the people involved in the incident
In serious crime cases, it is important that the cordon around the perimeter of the scene is policed at all times
Weather protection - An assessment of the susceptibility of the evidence to damage from the weather needs to be done
Protect from members of the public and animals coming into scene
Traffic control may also be required
Initial assessment - common approach path
Take as wide a path around crime scene as possible
Going in and out of the scene the same way so that you are disturbing the crime scene as little as possible = common approach path
Common approach path = a path that is made between the police cordon encircling a crime scene and the scene’s focal point (e.g. the body) in order to gain early and controlled access to the focal point
Initial assessment - zones
In the case of the ram raid example
Hot zone = store, and car
Warm zone = place where things go to before they go into the scene, minimises disruption, ensures things are clean so that DNA can be found
Cold zone = support zone, not the crime scene, can be used for planning area/break area/meeting area, media and family are usually situated in this area
Initial assessment - PPE requirements
Mask, hairnet, booties, double gloves, disposable suit
This kit is worn in order to avoid contamination of the evidence with material (especially DNA) derived from the person who was collecting it
Common approach path
Common approach path = a path that is made between the police cordon encircling a crime scene and the scene’s focal point (e.g. the body) in order to gain early and controlled access to the focal point
Reconnaissance (scouting)
Walk through scene
Usually when other experts and detectives are there and walking through
Once zones have been made
Gather information (CCTV; Witnesses) Gather as much information as possible and then start looking at physical trace evidence - starting with DNA (the one item that is most likely to be contaminated so is usually the focus of their intention) and then working through blood, fingerprints, footprints and then food wrappers etc and the physical exhibits often come last because they are the most durable
Primary reconstruction
Initial hypothesis - Were they looking for product? Looking for till? Part of a ring?
Discuss with other experts present
Forensic strategy
Formal or informal plan
Formal = something you go to a lot, certain things you want to do, time is not a factor (people aren’t there)
Informal = if people are still there/in the area, things can change at any time, focus on the most important thing first, if you have to leave scene ensuring that it is protected so that you can come back to it
Even the most formal of plans are subject to change
Resources – people; equipment
Review options and order of examination
formal plan
Formal = something you go to a lot, certain things you want to do, time is not a factor (people aren’t there)
informal plan
Informal = if people are still there/in the area, things can change at any time, focus on the most important thing first, if you have to leave scene ensuring that it is protected so that you can come back to it
Scene examination
Photograph and document the scene
Photographers come in early, allows for a reference point since they photograph it early and before the scene has been manipulated too much
Documenting the crime scene is done by making written notes that are augmented by photographs, video recordings and/or sketches as appropriate
Ensure it is noted how the physical evidence was found at the scene and the condition that it was in
Documentation might need to be used in court (if the case culminates into a trial) so needs to be good
It is important to record fragile physical evidence before it is recovered in case it is destroyed during the recovery process
All notes must be sufficiently clear and detailed to be of value to someone reading them a long time after the scene was processed
Crime scene sketches can be made or a computer can be used to generate a virtual reconstruction of the crime scene
Carry out forensic examination
Visual searching
Chemical testing of suspect stains (if required) - Usually blood, Anything else suspicious that looks biological also noted
Collection of evidence
Document evidence collection
Need a good record of things
Important for court
As more information comes to light:
Update reconstruction- Update until you have a pretty good idea of what may have happened
Scene examination order …
Initial action Initial assessment Reconnaissance Preliminary reconstruction Forensic strategy Scene examination
Forensic photography
Digital photography useful for rapid and effective image manipulation, can enable the overlapping of photographs
Digital photography can facilitate image enhances (give clarity), however the ease with which digital images can be manipulated means that their credibility in court may be diminished compared with conventional photographs
Video can be used to augment still photography in the recording of the overall appearance of a scene and the position of items of evidence within it
Scale is important to include in forensic photography
Still photographs can show the overall appearance of the scene
Each item of physical evidence that is found at the scene of a serious crime should be photographed before it is recovered or otherwise moved i.e. in situ - then can be photographed again in the lab with scale for better analysis
Photographs can also be used to preserve fragile pieces of evidence that might be damaged during their recovery
When a dead body is present at a scene, it should be photographed from several different angles using medium-range shots, close up shots of the injuries should also be taken
3D imaging systems are an emerging technology
Serious crashes
Varying severity
Example: Passenger burnt - identified with wallet, visual identification impossible so have to start backwards
Bomb threat
Studio - Photograph on scene (in place found) then photograph in the lab
Telling a story
Good notes
Postmortem identification
Fingerprint and ridges on hand can be inked and photographed to see if on database
Dental good for identification
Macro
Serial No. Scratched out … Revealed serial number through sanding it down as it changes the structure of the metal itself - able to reunite item with rightful owner
Reconstruction
Remake scene, compare to other ones still intact such as the cruise ship lifeboat scenes
partner organisations - FENZ, work safe, TAIC, CAA
FENZ = foreign emergency NZ
Fires… Difficult to determine arson - evidence damaged or completely destroyed often as a result of the fire
Search warrants
Match up to reports so that you can get the items back to the owners
Assisting ESR
ESR - houses that make methamphetamine can be searched and senior crime officers can come in and help photograph and catalog these kinds of scenes
CCTV
Electronic evidence is more and more prevalence
You leave a digital footprint always
general series of events when the police are classed to a crime …
Fresh scene identified by witness or victim - 111 informed - police show up and freeze scene as much as possible - senior crime officer and detectives assess and determine what needs to be preserved - then may call in ESR etc
