Unit 1: Crime Scene Management

Crime scene management is the systematic control of a location where a suspected offence has occurred, from the moment of first response until the scene is formally released. Its purpose is to preserve the evidential value of the scene so that physical traces can later reconstruct events and withstand scrutiny in court. The discipline rests on Locard's Exchange Principle (Edmond Locard, c. 1910): "every contact leaves a trace" — any person entering a scene both deposits and removes material.

• Chain of custody: The unbroken, documented record of who handled evidence, when, and why; a single undocumented transfer can render an exhibit inadmissible.
• Contamination control: Every entry risks adding foreign material or destroying existing traces; access is therefore restricted to essential personnel only.
• Integrity over speed: A scene is processed once and cannot be re-created; irreversible actions (moving a body, opening windows) are deferred until documented.
• Priority of life: Rendering medical aid and neutralising danger always precedes evidence preservation, even at the cost of some disturbance.
• The four core tasks: Secure, record, search, and recover — this unit addresses the differentiation of scene types and the first two tasks.

II. Indoor versus Outdoor Crime Scenes

Classification by environment and its effect on evidence handling

A crime scene is classified by its physical setting because the setting dictates how evidence behaves, how quickly it degrades, and how the scene must be protected.

A. Definition and basis of classification

The primary/secondary distinction concerns where the crime happened versus where evidence migrated; the indoor/outdoor distinction concerns the physical enclosure of that space.

• Indoor scene: A location enclosed by a structure — a room, dwelling, office, vehicle interior, or corridor — where the environment is largely controlled.
• Outdoor scene: An open or exposed location — a field, road, forest, or open water margin — where natural conditions act on the evidence.
• Mixed scene: A single incident spanning both (e.g., a body found in a house with a dragged trail into the garden), requiring both sets of protocols.

B. Differentiate between indoor and outdoor crime scene

The two scene types differ across environmental exposure, evidence stability, boundary definition, and processing constraints.

1. Indoor crime scene

   • Environmental control: Shielded from rain, wind, and sun; temperature and humidity relatively stable, so evidence degrades slowly.
   • Evidence stability: Fingerprints on smooth surfaces, fibres, and biological stains persist for extended periods.
   • Defined boundaries: Walls, doors, and windows create natural, easily secured limits; entry/exit points are finite and identifiable.
   • Contamination sources: Chiefly human — occupants, first responders, medical staff — rather than natural.
   • Lighting: Artificial and consistent, allowing methodical search without waiting for daylight.

2. Outdoor crime scene

   • Environmental exposure: Rain washes away blood and dilutes fluids; wind scatters lightweight trace; sunlight (UV) degrades DNA and biological material.
   • Evidence instability: Footwear and tyre impressions in soil are fragile and short-lived; must be cast or photographed urgently.
   • Undefined boundaries: No natural walls; the perimeter must be enlarged generously and marked with tape or cordons because the offender's route is uncertain.
   • Contamination sources: Natural (animals, insects, weather) plus onlookers over a wide, hard-to-control area.
   • Time pressure: Weather-sensitive evidence takes priority; protective measures (tents, covers) are erected before deterioration.

• Practical example: A gunshot indoors leaves a spent cartridge on a floor that stays where it fell for hours; the same cartridge outdoors may be displaced by wind or trodden into mud, so it is photographed in situ and recovered first.

C. Applications and limitations

The classification guides resource allocation but is never absolute.

• Application: Determines whether shelter, artificial lighting, or larger cordons are the first logistical need on arrival.
• Limitation: Vehicles and tents blur the boundary — a car is enclosed yet parked outdoors, demanding hybrid handling.
• Significance: Misjudging scene type (treating an outdoor scene as leisurely as an indoor one) leads to irreversible evidence loss through weather.

III. Securing the Crime Scene

Establishing control to preserve evidential integrity

Securing a scene means asserting physical and administrative control so that nothing is added, lost, or altered before documentation is complete. It is the first responder's primary duty after ensuring safety.

A. Purpose and principle

Security exists to freeze the scene in the state the offender left it, satisfying Locard's principle in reverse — minimising fresh contact traces.

• Principle of minimal access: The fewer people who enter, the fewer contamination events; ideally one path in and out.
• Principle of the widening cordon: It is always easier to shrink an over-large perimeter than to expand one after evidence outside it is destroyed.

B. Secure crime scene

Securing follows an ordered sequence from arrival to handover, protecting both people and evidence.

• Assess and ensure safety: Neutralise hazards (fire, gas, live weapons, hostile persons) and render medical aid to the injured before anything else.

• Establish the perimeter: Define an inner cordon around the immediate scene and, for serious cases, an outer cordon for staging and equipment; mark with barrier tape or physical barriers.

  • Indoor: Cordon the room and its access corridor; post an officer at the door.
  • Outdoor: Cordon generously to include likely entry/exit routes and discarded items.

• Control access: Maintain a scene log (entry/exit register) recording the name, role, time in, and time out of every person; establish a single common approach path to and from the scene.

• Preserve transient evidence: Protect fragile traces immediately — cover impressions from rain, shield the scene from crowds, prevent doors or windows being opened or closed.

• Detain witnesses and suspects: Separate them to prevent collusion and record initial observations.

• Hand over: Brief the incident investigator or forensic team, transferring the scene log intact.

• Common error: Allowing supervisors or medics to enter uncontrolled; each unlogged entry is a break in the chain of custody that defence counsel can exploit.

IV. Describing the Crime Scene

Creating the permanent, objective record

Describing the scene is the act of capturing its condition through notes, photographs, sketches, and video so that others can understand and reconstruct it long after release. Because the scene is destroyed by processing, the description is the evidence that endures.

A. Purpose and the four methods

Documentation must be objective, complete, and mutually corroborating; the four standard methods reinforce one another.

• Notes: A continuous written narrative recording time, weather, lighting, persons present, and every action taken.
• Photography: Visual capture at three ranges — overall (establishing), mid-range (relating an item to its surroundings), and close-up (detail, with and without a scale).
• Sketching: A measured line diagram fixing the position of items relative to fixed reference points.
• Videography: A continuous walk-through giving spatial context that stills alone cannot convey.

B. Describing crime scene

An effective description is factual, measured, and free of interpretation, following recognised conventions.

• Objectivity rule: Record what is observed, not what is inferred — "a red stain, approx. 5 cm, on the tiled floor," never "a bloodstain from the victim."

• Photographic scale: Every close-up is taken twice — once without and once with an L-shaped scale (ABFO No. 2) or ruler — so size can be verified and the image proven unaltered.

• Sketch measurements: Positions are fixed by established techniques.

  1. Rectangular (baseline) coordinates: Two measurements taken at right angles from two fixed walls — suited to enclosed indoor scenes with straight edges.
  2. Triangulation: Two distances from two fixed reference points, locating an item by the intersection of two arcs — suited to outdoor scenes lacking straight walls.

• Essential sketch elements: Title block (case number, date, location, sketcher), compass north arrow, scale or "not to scale" note, legend keying numbered items, and measurements.

• Progression of photography: Shoot from general to specific and before anything is moved; the sequence is logged so the order of capture is provable.

• Numbering and reference: Each item receives a unique exhibit number carried consistently across notes, sketch legend, and photographs, binding the four records together.

• Worked example (triangulation): A knife lies in a yard. Measure from fixed point A (corner of a shed) to the knife tip: 3.2 m. Measure from fixed point B (a gatepost) to the same tip: 4.5 m. On the scaled sketch, an arc of radius 3.2 m from A and an arc of 4.5 m from B intersect at exactly one point — the knife's fixed, reproducible position.

C. Significance of accurate description

The record's value lies in its permanence and its resistance to challenge.

• Reconstruction: Measured sketches and ranged photographs let analysts rebuild spatial relationships — trajectory, distance, and sequence — after release.
• Corroboration: When notes, photographs, and sketch agree, each reinforces the others' reliability in court.
• Admissibility: A documented, logged, and scaled record demonstrates that evidence was neither altered nor fabricated, sustaining the chain of custody established during securing.