Principles of Forensic Science: Crime Scene Management and Incident Protocol

Course Logistics and Procedural Overview

• Enrollment and Capacity Statistics:

  • Total enrollment for the course is approximately $267$ students.
  • The capacity of the tutorial room is $247$.
  • The lecturer noted that, theoretically, $20$ people would be required to sit on chairs (or be displaced) if everyone attended, but actual attendance usually allows for comfortable seating.

• Nature of Tutorials vs. Lectures:

  • The primary lectures focus on how chemistry is applied to forensic science.
  • The tutorials are designed for broader discussions of forensic science principles in general.
  • The sessions are group-discussion-based and emphasize learning from mistakes in a low-stakes environment.

• Tutorial Aims:

  1. Provide a step-by-step look at approaching and dealing with an incident/crime scene.
  2. Highlight common pitfalls and mistakes during scene management.
  3. Discuss approach and examination procedures.
  4. Examine incident management protocols.
  5. Discuss statistics in a forensic context.

• Graphic Content Warning:

  • The study of forensic science involves pictures of crime scenes, which may include deceased individuals.
  • Graphic images are generally redacted to ensure the person in the scene is unrecognizable.
  • Students are advised to reconsider the degree if they cannot tolerate viewing dead bodies.

Defining and Scoping a Crime Scene

• The Conceptual Definition:

  • A common public definition is "a location where a crime has occurred."
  • The Academic/Forensic Definition: A location where there is a "reasonable suspicion" that a crime has occurred. This adjustment is necessary because police often cannot be absolutely certain of a crime at the initial point of encounter. Legislation allows police to act based on this threshold of suspicion.

• Size of a Crime Scene:

  • Crime scene sizes are variable and can range from microscopically small to unfathomably large.
  • Small Examples: A single drop of blood; a computer or the Internet (digital scene); a cupboard (e.g., in a staged suicide); or a vehicle.
  • Large/Major Examples: Mass casualty events (e.g., Port Arthur); terrorist incidents involving vehicles (e.g., trucks in Christmas markets).
  • Maximum Scope Example: An airline shot down at $10,000$ or $30,000\,feet$ (e.g., over Ukraine or Russia). The scene covers a massive area where debris and victims rain down, requiring the FAA to reassemble the entire craft.

• Extended Scenes:

  • This refers to linked locations. For example, the site where a crime was committed and a separate location where the getaway car was dumped. They are technically separate but linked by the same incident.

Scene Discovery and the First Responder Phase

• Primary Discoverers:

  • Deceased individuals are often found by members of the general public, hikers, or park rangers.
  • Wildlife and Pets: Dogs are often the first to find decomposing bodies because of the attractive scents emitted during decay. Dogs may roll in the remains or retrieve bones (disrupting the scene) and bring them to their owners.

• Issues with First Discovery (The Public):

  • Contamination: Discoverers may leave dog fur, hair, DNA, saliva, or footwear impressions.
  • Scene Distortion: First aid attempts, such as the "kick" used to check for a response in a potentially drunken person or a corpse, can move evidence or the body.

• Initial Police Response:

  • The first officer on the scene (e.g., "Constable PC Plod") has several immediate tasks:
    1. Call for Backup: Request additional manpower and specialists.
    2. Preservation: Set up a cordon using crime scene tape.
    3. Start a Log: Record details of everyone present and their contact information to prevent them from disappearing and losing their testimony.
    4. Risk Assessment: Initial assessment for hazards (though deep assessment may be left to investigators).

Communication Protocols: CHALET and METHANE

• CHALET (Older UK Acronym):

  • C: Casualties (numbers and severity).
  • H: Hazards (present or potential).
  • A: Access (best routes for responders).
  • L: Location (exact coordinates/description).
  • E: Emergency Services (who is there and who is needed).
  • T: Type of Incident (aircraft, building, etc.).

• METHANE (New/Current UK Acronym):

  • M: Major Incident (Declaring this immediately triggers resources, overtime, and mobilization of personnel).
  • E: Exact Location.
  • T: Type of Incident.
  • H: Hazards.
  • A: Access.
  • N: Number and Severity of Injuries.
  • E: Emergency Personnel present/needed.

Chain of Command and Rank Structures

• The Tiered System:

  • Gold (Strategic): Head honchos making top-level decisions.
  • Silver (Tactical): Middle managers directing resources and prioritizing evidence collection.
  • Bronze (Operational): People on the ground making things happen.

• Queensland Police Service (QPS) Ranks (Top to Bottom):

  1. Commissioner (Gold): One person, based at Headquarters (Roma Street).
  2. Deputy Commissioner (Gold): One person; acts as Commissioner in their absence.
  3. Assistant Commissioner (Gold): Multiple individuals in charge of specific areas (Forensics, Terrorism, or Geographic regions).
  4. Chief Superintendent (Silver): Head of a police station.
  5. Superintendent (Silver).
  6. Inspector (Silver/Bronze crossover): Typically the rank required to be a designated scene manager for large incidents.
  7. Senior Sergeant / Sergeant (Bronze).
  8. Senior Constable / Constable (Bronze): The "boots on the ground" seen daily.

• The Default Silver Rule:

  • If a Bronze rank officer is the very first to arrive, they are Silver by default and are in charge of the scene until a true Silver rank arrives to relieve them. They cannot simply hand over responsibility to another Bronze officer.

Inter-Agency Coordination and the "Major Incident" Lead

• Competing Priorities:

  • Firefighters (Firies): Focused on fire suppression and structural safety.
  • Ambulance (Ambos): Focused on preservation of life.
  • Police: Focused on threat removal and evidence.

• The Post-2010 Shift:

  • Prior to $2010$, medical life-saving was almost always the priority. Following major terrorist incidents in the UK and France, protocols changed.
  • Police are now ultimately in charge during active threats (e.g., terrorists with automatic weapons) because they must neutralize the threat before paramedics can safely work.
  • Once the threat is removed, the police delegate priority back to medical personnel.

• The Military:

  • In peacetime, the military must be invited by the police to assist.
  • If they are present for a specialized task (like the Bomb Squad), they generally take over that specific role from the police.
  • In wartime, the military is in charge at all times.

Forensic Scene Management and Specialized Roles

• Scene Cordons:

  1. Outer Cordon: Manned by general police; keeps the public out.
  2. Inner Cordon: Manned by Forensic/Scenes of Crime Officers (SOCOs); keeps unauthorized police (curious detectives) and public away from sensitive evidence.

• Common Approach Path (CAP):

  • A designated entry/exit point in the cordons. It prevents investigators from "traipsing" over the scene and disturbing footprints or biological evidence.

• Specialized Investigative Personnel:

  • SOCOs (Scenes of Crime Officers): Collect DNA, fingerprints, and illicit substances.
  • Coroner/Pathologist: Required for a fresh body.
  • Anthropologist: Required for skeletal remains.
  • Ballistics/Firearms Officer: Deals with bullets or making firearms safe.
  • Bomb Squad (Military): Deals with IEDs/explosives.
  • Divers: Collect evidence/weapons from water (dams, rivers).
  • SES (State Emergency Service): Provide search volunteers, large searchlights, and sandbags for preservation.
  • Engineers: Consulted for long-term arson scenes/burnt-out buildings.

Evidence Hierarchy and Collection Decisions

• Significance and Relevance:

  • Investigators cannot collect everything (e.g., in a hoarder's house).
  • Evidence is prioritized based on its potential to link a specific person to the crime.

• The Hierarchy of Evidence:

  • Top Tier: DNA and Fingerprints (Specific to an individual).
  • Lower Tier: Fibers (e.g., blue denim fibers are generic/common).

• Prioritization Factors:

  1. Perishability: If evidence is about to be destroyed (e.g., footprints in snow melting or tide coming in), it is prioritized over DNA/Fingerprints.
  2. Destructive Testing: Some methods, like superglue fuming inside a car for fingerprints, can "write off" a vehicle. This cost/benefit is weighed by the police.
  3. Logistics: Large items (like a fire alarm in a wall) may lead to "chiseling out" parts of a structure.

• Political and Economic Pressures:

  • Closing a major artery like the Bruce Highway for a vehicular homicide investigation is incredibly expensive for the state.
  • Forensic teams may face immense political pressure to process the scene quickly so the road can reopen.

Statistics, Error, and Bayes' Theorem

• Instrument Error:

  • No forensic instrument is $100\%$ free of error.
  • Breathalyzer Example (Presumptive Test): Sources of error include calibration drift (worsens throughout the day), sample volume (breath provided), and environmental/instrumental uncertainty.

• The Prosecutor's Fallacy and Probability:

  • Scenario:
    • Drink driving rate: $0.1\%$
    • Device accuracy: $99\%$
    • False positive rate: $1\%$
  • If a driver tests positive, many guess the likelihood of guilt is high ($>75\%$).
  • Using Bayes' Theorem, given these specific parameters, there is actually only a $9\%$ chance that the person is actually drink-driving.

• The Role of the Expert:

  • Forensic scientists must convey these errors in court without undermining their work or lying to the jury about the existence of uncertainty.