Principles of Forensic Science Lecture Notes (SCIENCE SECTIONS) PDF

Preview

Summary

A completed exam guide covering all the information and diagrams for the science section of the subject. I also have a completed guide for the law part of the subject....

Description

MICHELA MURPHY

65242 Principles of Forensic Science Autumn 2020 Science Lectures Study Guide 1. 2. 3. 4. 5. 6. `!

Introduction to Crime Scene Investigation Marks and Impressions Introduction to Microtraces Introduction to Fingermarks Introduction to Forensic Taphonomy Introduction to Forensic Biology and DNA

1

MICHELA MURPHY

1. Introduction to Crime Scene Investigation! Aims - Who, What , when ,where, why & how?! - Who were the offenders and victims?! - What happened during the offence?! - Where were the location/s involved?! - When did the offence take place?! - Why did the offence take place?! - Motive; not always known! - How did the offence take place?! - An accurate and reliable record of the scene need to be produces !

- Follow the principle from the general to the particular ! - Preserve the scene/traces from further tress contamination ! - Document any entrance props to the arrival of the crime scene officer !

- Investigate the scene and research of relevant traces and exhibits !

- Traces of the event that occurred and traces that may link individuals to the scene need to be located, researched and recognised (or it will be lost forever)!

- Process techniques to detect latent traces on the scene ! - Fingerprint dusting ! - Collect the traces and exhibits of interest ! - Correct handling of evidence needs to be observed at all times to avoid irrecoverable damage to contamination!

- Assignation of unique ID to each item !

What is a Crime Scene? - Usually a location, can be people, objects or places. ! - Examiners examine the scene and collect evidence ! - Locations! - Primary: where the offence occurred ! - Secondary: objects relating to the crime ! - Start with this due to the elements ! - Examples: POI residence, Victims residence, Vehicles involved (secondary crime scene)! - An answer to a criminal event - Reported to police! - This is the first step! - Robbery, burglary, break and enter! - Homicide ! - Abduction! - Terrorism! - Sexual assault ! - Related to minor or major crimes!

2

MICHELA MURPHY

Minor (volume) crime: - No not include violent crimes or aggravating circumstances ! - Someone with a a weapon, with another person, threats of violence ect! - in NSW SOCOS are responsible for minor crimes! - Attend the scene ! - Use basic examination techniques to collect, protect and document the crime scene ! - Examples! - Theft ! - Malicious damage !

Major crime: - Attended by both CSO and sworn civilians ! - Involves advanced examination techniques! - Can include:! - homicide! - Sexual assault! - Assault! - Aggravated Robbery !

Other incidents and scenes: - can we called to scenes not related to an alleged crime! - Many relate to modes of death that are suspicious or unnatural ! - Examples:! - Suicide - Could be a staged homicide ! - Sudden or unexpected deaths - need postmorton results ! - Accidental deaths! - Deaths by misadventure - standing at a waterfall taking a selfie ! - Industrial accidents or deaths - work related ! - Other events we attend:! - search warrants - ! - Forensic procedures - taking evidence samples, bucket swabs, hair ! - Post-mortems - suspicious deaths, photograph, make notes, fingerprinting to identify bodies! - Taking / collecting samples for sexual assault identification kits (SAIK) at hospitals - swabs, finger nail clippings (assisted by a nurse).!

- Photographing wounds and injuries - at post mortem, at the hospital (to be present in court)! - Fingerprinting deceased persons - for identification ! - Critical incidents (police shooting) - pursuit where the car has crashed, death in custody in the cells (must be investigated) !

Aims of crime scene investigation: - Aims to help answer crucial questions! - Who were the offenders and the victims?! - Wha happened during the offence?!

3

MICHELA MURPHY

- Where were the location/s involved?! - When did the offence take place?! - Why did the offence take place? ! - ie. motivation - not always known! - How did the offence take place? ! - Fire scene ! - accidental, criminal, negligence! - The origin of the fire, the cause of the ignition, the development of the fire ! - Preserve, collect, document, and exploit the evidence ! - Preserve any traces, extend the crime scene is necessary, rescue the risk of contamination ! - Ie. ambulance entering the scene ! - Collect the evidence, package it safely and to preserve traces for processing ! - Packaging keeps everyone safe as well as protect the evidence in transit ! - Treat all items as infectious ! - Document the evidence, photograph, sketch, take notes ! - Still hardcopy notes, sketching is VERY important (need to measurements, where things are located on an item, ect)!

- Communication is important ! - Documentation allows you to record the events and facts. It is your memory of the crime ! - Look for traces to assist in reconstruction and linkage ! - Reconstruction: assist in deterring the circumstances of an event! - Linkage: associated two situations ! - Exploit the evidence by pressing it for all potential traces !

Examples of a fire investigation: - can be:! - Large - cover a large area! - Bush fires, factories ect! - Dangerous / toxic! - Structures are compromised and need to first be secured / checked by firefighters! - Messy ! - Lots of damage and debris (needs clearance from engineer to enter) !

Aims of the crime scene investigation - the trace: - the corner stone of forensic science is the trace ! - Traces are any material deposited on the crime scene by the POI and victim.!

- Examples! - a trace could be any item / material that links the following:!

4

MICHELA MURPHY

- Follows Locards principles of exchange ! - Important to remember !

Locards Principles of exchange: - “every contact leaves a trace”! - Linkages:! - Traces may be found at a scene that originated from the suspect/victim ! - This can be a material deposit! - May be the result of an action! - Two possibility for transfer! - Simple (single) : trace found on A comes from B! - Double: trace found on A comes from B, and the trace found on B comes from A! - Eg. Sexual assault! - Very compelling in court !

General to particular:

- Start with general, then move to particular!

Arrival at the scene - communication: - Examiner is contact and given basic information prior to arriving ! - address, contact person at the scene, brief overview of the crime ! - Upon arrival, you are given more information! - Useful to talk to witnesses, victims, other investigation ! - Witness are often wrong, they are in shock, could be hiding something to protect someone ! - Officer in charge will often give you relevant information. ! - TALK TO THEM! Get as much information as possible !

5

MICHELA MURPHY

- keep an open mind, not all information will be accurate ! - Information will evolve! - Between you being told and you arriving ! - From this information the examiner can:! - Who has entered the scene and what path they took ! - What may be contaminated from the first responders ! - Could be an active crime scene (not common)! - They are hiding on the scene ! - CCTV is an excellent resource !

Arrival at the scene - preservation: - You are expected to:! - Speak to officer at the scene ! - Confirm permission or warrant ! - Otherwise anything you do is illegal and not valid in court! - Asses existing preservation methods ! - Must be 50% larger than the scene ! - Always collect anything at a scene, you can always discontinue the evidence later ! - Assess hazards! - Conduct a risk assessment at a scene! - Especial with conducting procedures ! - lasers, using chemicals ! - Determine additional safety measures! - Could get flood lighting, equipment, divers ect ! - There are many resources and teams to call in for help! - Coordinate resources and examinations ! - Ensure there is an outer cordon ! - Secure any secondary scenes ! - Ensure inner cordon is appropriate ! - Confirm that police are taking a crime scene log !

Cadaver management: - important to ! - Document the position and state of the body within the scene ! - Clothing position, wounds, ect! - Document and preserve any traces that may be on their person ! - May involves! - Collecting visible traces off the clothing - don’t want to loose anything ! - Protecting hands - may have traces under their nails ! - Arranging collection of the clothes / jewellery / ligatures after that have been removed ! - Don’t take of neck ropes in suicide cases!

Safety and hazards: - Crime scene work is very hazardous !

6

MICHELA MURPHY

- Psychological ! - Scenes involving children, pregnant women, eg ! - Usually speak to a psychologist every few months,! - Becomes hard when you can relate to the crime! - Biological hazards! - Body fluids - can be infection / slip hazards! - Decomposing hazards ! - Environmental hazards! - Extreme temperature, sun exposure,! - Whether and wildlife on the scene ! - Physical hazards! - syringes, broken glass, sharp objects ! - Moving bodies! - Working in tight / cramped spaces ! - Chemical hazards! - Chemicals used by examinations ! - Can be at the crime scene. (eg lab / drug crime scene)!

Entering the scene: - Outer cordon ! - Only police & authorised persons can enter! - Prevent the general public and the media from coming in ! - Police monitor the entry and will have a log of who goes in and out! - Entry log can be used in court ! - Inner cordon: where crime scene examiners enter to exams the scene! - You can determine who goes in and out, Can say no to anyone of any rank !

Point of entry (POE): - where the offender enters a scene ! - Can be an open door / forces entry ! - Is an excellent source of evidence ( due to long periods of contact)! - Must determine the point of exit ! - May not be the same as the POE! - Usually difficult to determine the two ! - Sings of POE! - Broken glass (especially on the inside of the crime scene)! - Damage to an exterior door / window frames ! - Damage to locks / handles / latches!

Examination order: - Genreal sequence is:!

7

MICHELA MURPHY

- Don’t enter through the POE ! - You don’t want to destroy / contaminate any evidence ! - Alternate light search - work methodically, and do different patterns ! - UV (body fluids) , green laser, white light ! - Scene photography - work from general to particular ! - Prioritise evidence that will be destroyed ! - gunpowder, any outside traces, eg !

Principles: - aim to locate evidence and traces! - Incomplete searches lead to loss or destruction of evidence ! - Usually not accepted / compelling in course ! - Scenes include vehicles and buried remains ! - Remember the ABC on investigation (used by UK police)! - A - assume nothing ! - B - believe nothing or no-one! - C - Challenge everything !

Examination - light source search: - used to detect traces ! - Use a variety of angles (very important) and wavelengths - white , green, and UV. ! - Grazing angle (45)! - Floors are searched and cleared to allow a pathway through the scene to prevent loss of traces ! - Stepping tiles ! - Indicate areas of interest with markers and flags!

Documentation: - saves yourself in court (can be used)! - Write EVERYTHING, including conversation ! - Documenting includes:! - Note taking, sketching, imaging, chain of custody ! - Chain of custody: where your exhibit moves throughout its life!

Imaging: - Documentation techniques include: ! - Record video, Still images, 360 degree imaging ! - CSE’s use digital SLR cameras to record the scene in a series of still images ! - Should start past the outer cordon of the scene and move inwards! - General scene, Midrange, Close up! - Purpose ! - Present in court - court members haven’t been to the scene, so it is your job to fill them in ! - Refresh your memory ! - Shows the relationship between items !

8

MICHELA MURPHY

Notetaking: - contemporaneous notes is extremely important! - Notes must:! - Be make in ink (no pencil, no correction tape)! - Be in chronological order! - Include your observation and test results ! - Be legible and understandable !

Sketching: - provide information that cannot necessarily be captures with a camera ! - Position of things and measurements (x and y measurements), Layout of a scene (floor plan), Help to refresh memory !

- Used to make Computer Aided Design (CAD) plans to be shown in court ! - CSE may be required to make multiple sketches at a scene ! - Other areas to sketch:! - POE (May be a unique or unusual situation) ! - Property / dwelling ! - Room where the weapons were found ! - Room where the offence took place ! - The weapon !

Collection of traces: - things are collected in different ways ! - Trace includes ! - Hand picking e.g. Actual exhibit ! - Plucking e.g. Fibres ! - Swabbing e.g. Trace DNA / blood ! - Lifting e.g.Fignerprints ! - Photographing e.g. Method of collection of a trace ! - Sifting e.g .A grave ! - Sorting !

Packaging of traces: - Very important as it protects the evidence and that person handling the evidence ! - Paper bags / cardboard boxes is usually used at scenes in Australia ! - Except drugs / money ! - Need safety warning on packaging for:! - Sharps, Glass, Anything!

9

MICHELA MURPHY

2. Marks and Impressions! LECTURER: CLAUDE ROUX

History -

Hans Gross! Rodolphe Archibald Reiss! Edmond Locard! August Vollmer! Paul Kirk! Stuart Kind!

Marks and Impressions - Impressions: any markings that are produced when on object comes into contact with another, leaving behind an indentation or pattern !

-

e.g. fingerprints ! Footwear impressions! Tyre marks ! Tool marks ! Firearm marks ! Bite marks !

- Mark and impression can be either! - Two dimensional ! - Positive! - Transfer of residue onto a surface ! - e.g. bloodied footmark! - Negative! - Removal of residue from a surface ! - e.g. footmark in flour ! - Latent! - Invisible to the naked eye ! - Three dimensional ! - e.g. foot wear impression in soil or snow !

Footwear Impressions - can be sock or shoe sole impressions ! - Useful in establishing a timeline of events ! - Can give an indication of routes of entry ! - Number of people involved! - Their respective roles and movements ! - Path taken ! - Point of exit ! - Obtain a link between the shoe and the crime scene !

10

MICHELA MURPHY

- Can link to different crime scene (serial activity)! - At the crime scene ! - Special attention should be paid to the following areas:! - Point of entry ! - Potential routes in the crime scene ! - Exit points ! - Near areas of other footwear impressions ! - Footwear impressions are often overlooked and can be damaged during life-saving efforts ! - Can be incredibly useful for localising areas of interest for subsequent trace searches ! - Footwear impressions must always be considered when assessing potential traces to collect ! - For 2-D footwear impressions! - Photography is the best tool to capture it; use grazing angle light photography ! - Gelatine lifters can be used to collect and preserve the impression ! - For 3-D impressions! - Photography is best (use light sone at different angles to get all different degrees of detail)! - Then a cats is made to collect the impression ! - Comparison ! - When considering impressions, different characteristics are classified as either :! - Manufactured (or class) characteristics ! - General patterns / shapes ! - Brands / logos! - Size! - Width ! - Acquired (or individual) characteristics ! - Wear patterns ! - Cracks! - Scratches ! - Gouges! - Imbedded rocks or gravel !

- The more acquired characteristics an impression has, the more valuable it becomes !

Value of General Pattern - Interpretation !

11

MICHELA MURPHY

- issues: similarity of patterns!

- Occasionally manufacturers characterises can form random differences that may assist in excluding different impressions !

Value of Wear And Tear - Progression of wear and tear on an outsole (of Reebock aurora) as a function of time !

- Relative values of characteristic wear and tear observed on shoe outsoles !

Tyre Marks - Can be either 2-D or 3-D depending on the surface the impression is made on !

12

MICHELA MURPHY

13

- Tyre profiles on asphalt is rarely distinguishable ! - Unless in the cases of sudden braking ! - Tyre marks can lead to ! - The identification of the brand name and model of the tyres ! - Using catalogues published by the manufacturers and by the suppliers, or with a computerised data base!

- The identification of the brand name and model of the vehicle ! - The determination of the direction taken by the vehicle(s)! - The identification of the tyre ! - Characteristics considered ! - Wheel base (distance from front axel to rear axel)!

-

Front and rear tyre tread stance ! Tyre circumference and tyre radius! Turning diameter! Imprint width ! Tyre pattern (huge variability)! Imprint of a letter on the shoulder of the tyre, and positions of this letter in relation to the pattern! Wear marks ! Depth of the pattern ! Abnormalities / individual characteristics (stones, cuts, ect)!

- For 3-D imprints! - Photography ! - Possible enhancement with a grey auto paint spray ! - Casting with dental stone ! - For 2-D imprints ! - Photography! - (transfer using a lifting device is often problematic due to the material the impression is on e.g. blood, oil, ect)!

- It is important to ! - Determine the direction of driving ! - To differentiate the front wheels from the back wheels ! - Take note of all the required measurements ! - Comparison ! - Test prints by inking the tread of a mounted tyre and driving the car over a long paper band! - Each turn should be noted!

MICHELA MURPHY

14

Tool Marks - Tool marks are a common type of trace ! - Particularly in break and enter cases! - Different tools will leave different impressions on surfaces ! - Tool marks are commonly found in ! - Doorways / window frames ! - Wood or paint debris near a window ! - Safes ! - Tool marks will have manufactured characteristics !

- But they will gain aquarium characteristics over time !

- Major interpretation issue! - Acquired characteristics are not permanent ! - Excessive use can destroy any individual characteristics ! - Care must be taken when interpreting tool mark results ! - Care must also be taken when handling a suspect tool ! - Do not want to damage the individual characteristics ! - The suspect tool must never be placed into the tool mark ! - This may alter the mark and call into question the integrity of the trace ! - Collection of the trace ! - Entire object or the part of the object bearing a tool mark ! - Cast of the mark (after photography) when removal of the tool mark is impractical !

- Comparison material should also be collected (when possible) in order to make comparison prints on the same type of surface !

- Tool mark is observed using the naked eye and under a steromacroscope !

MICHELA MURPHY

-

15

Detection and collection of residue which could come from the tool ! General shape ! Size! Nature of the instrument ! How many instruments ! Identification of serial burglaries made with the same tool !

- The suspect tool is examined under the naked eye and under the steromacroscope ! - Detection of individual characteristics and residues which could come from the object being cut or struck!

- The tool is then used to produce test tool marks ! - On soft metal / mat...