Unit 3: Documentation of Crime Scene

Crime scene documentation is the systematic recording of a scene's physical layout, evidence and spatial relationships so that the scene can be reconstructed later in court, long after it has been released and altered. It rests on the principle that no single method is sufficient: notes, sketches and photographs are complementary, each compensating for the blind spots of the others. Documentation follows Locard's exchange principle in spirit — every item and its position must be fixed before collection destroys the context.

I. Foundations of Scene Documentation

Documentation begins the moment a scene is secured and proceeds from the general to the specific, never disturbing evidence until its position is recorded.

• Threefold record: Notes (written observations, time, weather, personnel), sketches (scaled spatial relationships), and photographs (visual reality) together form the complete record; a sketch shows measured distances a photo distorts, a photo shows detail a sketch omits.
• Chain of custody: Every documentation act is logged with date, time, and the recorder's name so the evidence remains admissible and traceable.
• North orientation: Every sketch carries a compass arrow (conventionally pointing to the top of the page) so directions are unambiguous.
• Fixed reference points: Objects are located relative to permanent, immovable features (walls, doorframes, kerbstones) that will still exist when the scene is revisited.
• Two-sketch convention: A rough sketch is drawn at the scene freehand and never altered afterward; a final (finished) sketch is prepared later, to scale, from the rough sketch's measurements.

II. Sketching the Indoor Crime Scene

Indoor sketching maps evidence within a bounded, walled space, exploiting the geometry of rectangular rooms and fixed structural features as reference lines.

A. Preparing the Rough Sketch (Indoor)

The rough sketch is the on-site, freehand master record from which all later drawings derive.

• Not to scale: Drawn freehand on graph or plain paper; proportions are approximate but every measurement is written in as a numeral (e.g. "table edge 1.2 m from north wall").
• Essential elements: Case number, address, date, time, sketcher's name, compass arrow, and a legend keyed with letters or numbers to each item of evidence.
• Measurement discipline: Two people measure with a steel tape; distances are recorded to fixed points and read aloud and confirmed to avoid transcription error.
• Never redrawn: The rough sketch is preserved as originally made; corrections are struck through, not erased, keeping its evidentiary integrity.

B. Preparing the Final Sketch (Indoor)

The final sketch is a clean, scaled drawing produced away from the scene for presentation.

• Drawn to scale: A stated ratio (e.g. 1:50, meaning 1 cm on paper = 50 cm actual) lets viewers derive any distance directly from the drawing.
• Prepared using instruments or CAD: Rulers, drafting tools or software (e.g. dedicated crime-scene mapping programs) produce precise, legible lines.
• Selective detail: Clutter is removed; only relevant evidence, fixed features and the legend remain, so the finished sketch communicates clearly to a jury.

C. Different Sketching Methods (Indoor)

Indoor scenes are measured using coordinate-based methods suited to walled geometry; the two dominant approaches are contrasted below.

1. Rectangular coordinate method: An object is fixed by two measurements taken at right angles from two adjacent walls.
   • Example: a pistol lying 0.8 m from the north wall and 1.5 m from the east wall is plotted at the intersection of those two perpendiculars — ideal for square rooms.
2. Triangulation method: An object is fixed by measuring straight-line distances from two widely separated fixed points (e.g. two corners of a doorframe).
   • The two arcs intersect at the object's position; superior when walls are irregular or the reference points are not perpendicular.
   • Baseline method: A single reference line is run between two fixed points; each object is located by its distance along the baseline and its perpendicular offset from it.
   • Polar (azimuth) coordinate method: From one fixed point, an object is fixed by an angle and a distance — useful for large rooms photographed with a total station.

III. Sketching the Outdoor Crime Scene

Outdoor sketching maps evidence across open ground that lacks convenient perpendicular walls, so it relies on portable or natural fixed points and larger scales.

A. Drafting the Rough Sketch (Outdoor)

The outdoor rough sketch captures a wide area quickly under variable field conditions.

• Weather and terrain noted: Wind, rain, lighting and ground type are recorded because they affect evidence and later interpretation.
• Reference points selected on arrival: Trees, lamp-posts, kerbstones, building corners, and utility poles serve as permanent markers; GPS coordinates supplement them where no fixed feature exists.
• Larger measuring tools: Measuring wheels and long tapes replace short indoor tapes; distances may run to tens of metres.

B. Drafting the Final Sketch (Outdoor)

The finished outdoor sketch converts the field data into a scaled, oriented plan.

• Smaller scale ratio: A larger area demands a compressed scale (e.g. 1:100 or 1:200) so the whole scene fits the page.
• Elevation where relevant: Slopes, ditches or staircases are indicated with contour notes or a supplementary elevation view, since terrain height affects trajectory and blood-flow analysis.
• Integration with maps: GPS points let the final sketch be overlaid on a survey map, tying the scene to a verifiable geographic frame.

C. Different Sketching Methods (Outdoor)

Outdoor scenes favour methods that need only one or two established points, contrasted below.

1. Triangulation method: Preferred outdoors because two fixed natural points (two tree bases, a pole and a corner) fix each object without any right-angle assumption.
   • Example: a shell casing 6 m from a lamp-post and 9 m from a fence corner is plotted where the two arcs cross.
2. Baseline method: A rope or tape is stretched between two fixed points to form a datum line; each object's distance along and perpendicular offset from the line are recorded — efficient for long, narrow scenes such as roadsides.
   • Polar/azimuth method: A transit or total station at one station point records bearing and distance to each item, then plots them; suited to very large, open scenes.
   • Grid method: The area is divided into labelled squares (A1, A2, B1...) with staked lines, and evidence is located within its cell — used for dispersed evidence like scattered debris or skeletal remains.

IV. Recording the Crime Scene by Photography

Photography preserves the scene's visual truth in detail no sketch can hold, providing a permanent, objective image of evidence in its original position.

A. Purpose and Principle of Crime Scene Photography

Photographs must depict the scene fairly and accurately, without distortion, addition or removal of anything.

• Progressive coverage: Shots move from overall (whole room or area), to mid-range (an object relative to its surroundings), to close-up (the item itself filling the frame).
• Two close-ups per item: One without a scale to prove nothing was altered, one with a scale (ABFO No. 2 ruler or L-scale) placed level with the evidence for accurate size reproduction.
• Photo log: Each frame is logged with number, time, subject, direction faced, and camera settings, tying every image to the notes and sketch.
• Overlapping sequence: Photographs are taken so adjacent frames overlap, allowing the full scene to be mentally reassembled.

B. Recording the Indoor Crime Scene by Photography

Indoor photography contends with confined space and artificial or absent light.

• Wide-angle lens for overalls: A short focal length captures whole rooms from corners; four corner shots document a rectangular room completely.
• Controlled lighting: Electronic flash, bounce flash, or oblique (side) lighting reveals surface detail such as dust footwear impressions on flooring.
• Fixed vantage points: Overall shots taken from each corner and from ceiling height (where possible) minimise blind spots created by furniture.
• Painting with light: In dim interiors, a long exposure with a moving handheld flash evenly illuminates a large dark room.

C. Recording the Outdoor Crime Scene by Photography

Outdoor photography exploits natural light but must manage its variability and scale.

• Natural light management: Shots are taken with the sun behind the camera; harsh shadows are softened with fill flash or a reflector.
• Elevated overalls: A ladder, drone or nearby high ground gives an overhead perspective of large scenes, showing spatial spread that ground-level shots miss.
• Reference markers in frame: Evidence markers (numbered tents) and a north indicator are included so open ground with few landmarks remains orientable.
• Time-sensitivity: Perishable evidence (tyre marks, footprints, blood on soil) is photographed first before weather degrades it, and re-shot as light conditions change.

D. Applications and Limitations of Photographic Recording

Photography's evidentiary strength is bounded by its inherent distortions.

• Applications: Supports courtroom presentation, scene reconstruction, and later comparison; permits examination of detail invisible during the on-site visit.
• Perspective distortion: A photograph flattens depth and can exaggerate distances, which is precisely why the scaled sketch remains indispensable alongside it.
• No measurement substitute: Photographs record appearance, not true distances; the sketch supplies the metric data the image cannot.