Crime Scene Investigation Notes

Introduction

  • Actions taken at a crime scene are tested in court.
  • The crime scene is where evidence is located.
  • Investigators must systematically search for evidence, regardless of its size or shape.
  • Familiarity with search methods is crucial for evidence collection.
  • Mistakes by investigators can hinder prosecution, while a systematic approach increases the likelihood of conviction.

The Process of Scene Investigation

  • Scene investigation is organized, methodical, and logical.
  • Investigator actions must be correct, objective, systematic, and thorough to maximize information retrieval.
  • The scene-of-incident investigation requires procedures to be followed sequentially.
  • The process is determined by crime specifics: when, where, who (suspect), and victim communication ability.
  • Three conditions for success:
    • Organization
    • Thoroughness
    • Caution
  • Investigators should revisit the scene and use different search methods as needed.
  • Benefits of a methodical approach:
    • Thorough and legal search
    • Swift and efficient processing
    • Thorough scene documentation
    • Correct methods for evidence recovery
    • Appropriate resource use
    • Recovery of all pertinent evidence
    • Proper safety precautions

Investigative Phases

  • Pre-investigation: starts with the first officer's arrival.
  • Investigation: starts with documentation and then the scene search.
  • Post-investigation: the finishing phase.

Pre-investigation Phase

Control and Protection of the Scene on Arrival

  • First officer responsibilities:
    • Separate and isolate suspects and witnesses.
    • Prevent disturbances, destruction, and contamination.
    • Protect physical evidence.
    • Reduce harm risk to responders, victims, and witnesses.
    • Determine if the scene is major or minor to assess support needs.
    • Identify physical evidence and potential eyewitnesses.

Assessment and Walk-Through Phase

  • The first officer's actions are critical for investigation success.
  • Maintain command of the scene to prevent loss of evidence due to unauthorized personnel.
  • A walk-through assesses the scene of the incident to determine the nature, extent, and perimeter of the scene.
  • The investigator determines the perimeter or the scene.
  • Once the perimeter has been determined, the scene should be cordoned off.
  • Officers should analyze the scene from a distance.
  • The investigator or officer should then answer the following questions:
    • Why am I here?
    • What is the purpose of my visit?
    • What has happened here?
    • How am I going to solve the problem or the crime?
    • What assistance and experts do I need to solve the problem or the crime?
  • General rule: look, observe, think, and do not touch.
  • Assess circumstances for a systematic plan to identify evidence.
  • Determine access/exit routes for officials/emergency personnel, avoiding suspect routes.
  • Precautions are needed to preserve evidence along unavoidable routes, e.g., photographs or covering exhibits.
  • During this phase the investigator will sketch and photograph the scene, note the location of all possible evidence and mark the visible evidence.
  • Mark visible evidence with labels or markers.
  • Common mistakes to avoid:
    • Unnecessary handling of objects
    • Trampling footprints
    • Leaving contaminants (cigarette butts)
    • Moving items
    • Adding clues (hair)
    • Using facilities
    • Switching electronic equipment on or off
  • Restrain from actions that jeopardize investigations in court.

Investigation Phase

Documentation of the Scene

  • Begins with documentation and searching of the scene.
  • Note-taking should be done immeditaley. Record facts and the scene as they stand, enabling instant recall.
  • Photograph physical evidence, as it is the best way to quickly and accurately document evidence and the scene.

Methods Used for Collecting Evidence

  • Collection links evidence to a suspect.
  • Techniques prevent damage and contamination.
  • Circumstances dictate technique.
    • Handpicking: Used for visible items, requires gloves, and tweezers for small items.
    • Removal of the whole object: Used when objects are too large or if objects have evidence materials deposisted inside or on it.
    • Pipetting: Collect liquids with a disposable pipet.
    • Tape-lifting: Gather trace, microscopic material from car seats, rugs, or clothes using transparent tape.
    • Sweeping: Collect small pieces of evidence in large areas, such as debris in a car trunk.
    • Vacuuming: Used only when necessary for small pieces, requires equipment to be clean before and after use.
    • Swabbing: Collect particles or body fluids with dry or moistened swabs.
    • Cutting: Cut stained areas from larger objects for examination.
    • Casting: Create casts of footprints and tire prints.
    • Metal detection: Locate hidden metal evidence, such as a firearm.

Methods and Procedures Used for the Packaging of Evidence

  • Package, label, and store evidence appropriately.
  • Package all items separately in unused containers to avoid cross-contamination.
  • Packages used to contain the evidence should be completely sealed so that not even the smallest trace of evidence can fall out or leak out of the packaging.
  • Temporary containers can be used if the correct container is not at hand, but the process must be recorded in detail.
  • Small items may be wrapped in pre-folded paper and placed in fully sealed polythene bags.
  • Dry cloth items and shoes may be sealed in paper bags.
  • Wet cloth items may be sealed in polythene bags and then frozen.
  • Items with hydrocarbon-based fuels are packaged in nylon bags and closed with airtight swan-neck seals.
  • Brown paper bags are used to package soil samples or items of clothing because the sample could rot and decay if placed in polythene bags.
  • Boxes are used for sharp objects such as glass, which are taped to the inside bottom of the box.
  • Circular plastic tubes (termed knife tubes) are used for packaging sharp instruments such as knives or screwdrivers.
  • Nylon bags are used for fibre debris or for items that have been in contact with explosives.
  • Plastic bags or plastic containers should not be used for organic matter because plastic accelerates the deterioration of biological specimens and causes accelerants to evaporate.
  • Pairs of things, such as socks and shoes, are separated and packaged into separate bags.
  • Polythene and paper bags should be folded over twice before sealing.
  • Double-wrap items of physical evidence by placing the packaged item into a second sealed container.
  • Evidence submitted to court must be in its original form and not tampered with.
  • Use wax seals to seal evidence in containers or sealed bags.

Chain of Custody

  • Each item of physical evidence must be labelled.
  • Each label has spaces that must be signed and dated by each person who takes responsibility for the item, from the moment it is collected to the time at which it is destroyed.
  • The chain of custody means:
    • Each person who handles evidence signs to indicate when the evidence was received and when it was passed back to storage
    • Each person records what has been done with the evidence on which date
    • Each person then replaces or stores the evidence in its secure storage location.
  • The investigator should ensure that the following information is recorded on the label:
    • Nature of the contents
    • Source of the evidence
    • Date and time evidence was sealed
    • Signature and printed surname of collector
    • Sequential numbering and the unique identifying case number

Search Methods

Investigator Considerations

  • Determine the search boundary.
  • Establish an effective search pattern.
  • Give clear instructions to personnel.
  • Coordinate personnel effectively.
  • Determine when to terminate the search.
  • Determine what evidence was collected.
  • Discuss preliminary findings with the team.
  • Discuss potential testing and sequence.
  • Arrange for extra lighting and protective cover.
  • Account for time and temperature influencing evidence.
  • Secure the scene to prevent contamination.

Recognized Search Methods

  • Strip method
  • Spiral method
  • Wheel method
  • Zone method
  • Grid method
  • Lochner-Zinn Vertical search method
Strip Method
  • Start at one end, walk to the other, turn, and repeat parallel to the original path.
  • Divide the scene into 1-meter strips.
Advantages
  • Can be used indoors and outdoors.
  • Effectively traces small to medium objects and footwear impressions.
  • Can be performed by one or more investigators.
  • Uncomplicated and thorough.
Disadvantages
  • Requires manpower for large areas.
  • Uneven terrain can be problematic.
  • Coordination and control can be hampered.
  • Time-consuming in large areas.
  • Can cause confusion if the central point of the scene contains a high concentration of crime information, could hamper the investigator’s control of the scene and disturb the scene.
Spiral Method
  • Start at the outer boundary and move in a circular manner towards the center.
Advantages
  • More suited to outdoor scenes.
  • Most effective if used to search small areas.
  • Useful for locating pieces of information near the central point of the scene
  • Less manpower is needed.
  • Effective entry and exit routes.
  • Can be combined with zone and wheel methods
Disadvantages
  • Time-consuming.
  • It is most effective if used to search small areas
  • Risk of damaging or destroying evidence while walking from the center is high if the pattern is reversed
  • Vital evidence may be overlooked if only one investigator conducts the search.
Wheel Method
  • Start at the middle of the scene and then move to the outside.
Advantages
  • Information which is relatively far from the scene can be located using the wheel method, as the action of ‘moving out’ can ripple outwards to cover the vicinity of the scene of incident.
  • Can define definite outlying boundaries.
  • Can be combined with inquiries in the vicinity of the scene.
  • Less Manpower needed.
Disadvantages
  • The scene could be disturbed and evidence destroyed or contaminated because the search starts at the central point.
  • Investigators should repeat the search several times depending on the size of the circle and the number of searchers.
  • The relative area to be searched may be too large.
Zone Method
  • Divide the scene into equally sized sections, assigning one searcher to each.
Advantages
  • Most effective at outdoor scenes or spacious indoor rooms.
  • Effective in flat, open spaces.
  • Thoroughness increased by rotating investigators.
  • Can be used with other methods (e.g., grid method).
  • Useful for recording bloodstain patterns, firearm projectiles, and trajectories.
Disadvantages
  • May require many investigators.
Grid Method
  • Divide the scene into cross-sections.
  • Search a strip along one axis (east to west), then return and cover the same area in a north-to-south axis, moving against the grain of the earlier lanes.
Advantages
  • Can be used effectively indoors and outdoors.
  • Acts as a double-check of the search area.
  • Useful in uneven terrain.
  • Valuable when searching for small items of evidence.
  • Each section is searched several times.
Disadvantages
  • May require many investigators.
  • Time-consuming if only one investigator searches a large area.
  • Can negatively impact motivation if nothing is found initially.
Lochner-Zinn Vertical Search Method
  • Used for accurate documentation of evidence on walls inside buildings.
  • Uses an overhead projector with a grid projected onto the wall.
  • Squares of the same size are projected against the relevant wall or surface.
Advantages
  • Provides a systematic way to search a vertical surface.
  • Specialised training is required to make sure that the grid is projected without a keystone effect.
  • Focuses attention on a manageable portion of the surface, one square at a time.
  • The relative position of each exhibit, for example, blood spatters, can be measured in the context of a matrix and later reconstructed in court.
Disadvantages
  • The instruments and especially the use of an overhead projector require a constant power source.
  • The grid lines are not virtual lines, as for example in the spiral search method, but visible lines projected by the equipment onto the surface.
  • The method has a time-consuming duration.
  • Specialist equipment must be at the disposal of the technician or investigator in order to project the grid against the surface.
  • Accurate measurements are required to mark where the equipment was positioned in order to reconstruct in court the way the method was used.

Post-investigation Phase

Release of the Scene

  • The scene is released when all facts, evidence, information, and answers have been obtained.
  • Ensure all physical evidence has been documented and collected.
  • Remove all equipment and ensure the scene is clean.
  • Report and address any dangerous materials or conditions.
  • Re-entry may require a search warrant.
  • The release is done only after the final survey has been completed.
  • The survey will determine if the objectives were met and will review all the activities that had taken place at the scene.
  • Ensure documentation contains:
    • Time and date of release
    • Names of releaser and recipient
    • Signature from the recipient
    • Endorsement of security transfer
  • Junior investigators should use a checklist.

Analysis of the Evidence

  • Conducted by trained experts, often from forensic science laboratories.
  • External experts can be used in high-profile cases.

Conclusion

  • The search for evidence starts during pre-investigation with scene control.
  • An assessment and walk-through are then conducted.
  • Documentation of a crime scene is an important aspect in the investigation phase
  • During the investigation phase, various methods and procedures can be used to collect evidence.
  • The post-investigation phase is concluded when the evidence is analyzed and the results made available to the relevant investigators.