Comprehensive Notes on Crime Scene Searching, Documentation, Evidence Collection, and Chain of Custody

Four Primary Phases of Crime Scene Investigation

  • Phase 1: First Response
    • Initial arrival, securing the scene, and addressing immediate threats.
  • Phase 2: Initial Assessment & Searching
    • Evaluating the scene context, performing a formal walkthrough, and systematically locating evidence.
  • Phase 3: Collection & Processing
    • Documenting, packaging, and preserving evidence to avoid contamination.
  • Phase 4: Final Assessment
    • Cross-checking logs, ensuring complete recovery, cleaning up, and releasing the scene.
  • National Guidelines Reference Standard
    • Current recommendations for crime scene procedures can be referenced via the National Institute of Standards and Technology guidelines standard: https://www.nist.gov/sites/default/files/documents/forensics/Crime-Scene-Investigation.pdf.

First Response and Incident Management

  • Dispatch Protocols and Scene Notification

    • Call Received: A member of the public or involved party calls the police.
    • Unit Dispatch: A patrol unit is dispatched to the scene. Emergency Medical Services (EMS\text{EMS}) and Fire Department personnel may also be dispatched concurrently.
    • Patrol Discovery: Patrol officers encounter a person or scene independently while on duty and conduct preliminary investigations until additional assistance is required.
    • Search Warrants: When a search warrant is issued, police officers, detectives, and Crime Scene Investigators (CSIs\text{CSIs}) are dispatched together as a coordinated team.

  • Primary Duties of the First Responder

    • Approach and enter the scene safely.
    • Check for immediate physical threats.
    • Provide immediate emergency medical care to injured parties.
    • Control all individuals present at the scene.
    • Establish preliminary scene boundaries.
    • Thoroughly document all initial actions taken.
    • Turn over scene control to the lead investigator.
    • Accomplish all preliminary duties without significantly contaminating the crime scene.

  • Threat Management and Priority Assessment

    • Threats to Victims:
      • Ongoing criminal acts.
      • Acute physical trauma.
    • Threats to Personnel:
      • Armed or dangerous culprits.
      • Biohazards (e.g., bloodborne pathogens).
      • Chemical hazards.
      • Physical hazards.
    • Threats to Case Integrity:
      • Escape of the culprit.
      • Damage or destruction of physical evidence.
      • Loss or dispersion of eyewitnesses.
    • Active Shooter Priority: During an active shooter incident, the single highest priority is containing the threat.

  • Crowd Control and Person Management

    • Identify Individuals Present:
      • Suspects
      • Witnesses
      • Victims, family members, and friends
      • Bystanders
      • Medical personnel
    • Access Control: Exclude every individual who is not explicitly authorized to be within the perimeter.
    • Witness Isolation: Immediately separate eyewitnesses from one another to prevent collusion, memory contamination, or altered statements.

  • Securing and Establishing Scene Boundaries

    • Primary Goal: Prevent scene contamination by actively controlling and directing all human movement on the scene.
    • Physical Control Tools:
      • Crime scene barrier tape.
      • Rope or traffic cones.
      • Floor tape marked walkways for interior scenes.
    • Areas to Include Within Boundaries:
      • The primary scene where the crime took place.
      • Any secondary scenes linked to the event.
      • Points and paths of entry and exit used by perpetrators or victims.
      • Locations where victims or evidence may have been moved.
      • Any location reasonably likely to have been walked on, driven over, or touched by the culprit.
    • Areas to Exclude From Boundaries:
      • High-traffic public areas unnecessary to the investigation.
      • Inaccessible physical locations.

  • Command Post Establishment

    • Communication Nexus: Functions as the central hub to share intelligence, assign investigative tasks, and dispatch specialists.
    • Equipment Holding Area: Serves as a staging area for tools and testing equipment outside the secure perimeter zone.
    • Rest Area: Provides a physical space for scene personnel to rest during extended operations.
    • Deployment: Can be established using a mobile Command Post vehicle.

Crime Scene Investigator (CSI) Qualifications and Roles

  • Employment Classifications: Investigators can be sworn police officers or educated civilians.
  • Educational Requirements: Ranges from a High School GED to a Bachelor of Science (BS\text{BS}) degree.
  • Compensation: Typical annual salary ranges from $30,000\$30{,}000 to $60,000\$60{,}000 per year.
  • Background Requirements: Must maintain a clean criminal background record.

Scene Assessment Procedures

  • Preliminary Assessment (Building Context)

    • Core Objective: Answer the primary question: "What do I need to do?"
    • Consultation: Speak directly with first responders to gather initial statements and context.
    • Safety Evaluation: Evaluate ongoing scene safety and hazard mitigation needs.
    • Boundary Assessment: Evaluate established perimeters for expansion or reduction.
    • Path Selection: Select clear walking paths through the scene to minimize footprint contamination.

  • Formal Walkthrough (Initial Reconstruction)

    • Core Objective: Answer the primary question: "What happened here?"
    • Crime Identification: Determine what specific crime, if any, has been committed.
    • Point of Entry/Exit Analysis: Identify potential entry points and record whether doors/windows are open, locked, or unlocked.
    • Disturbance Evaluation: Inspect for damaged or displaced items that indicate a physical struggle.
    • Activity Indicators: Check signs of recent activity, including prepared meals, cleaning supplies, active televisions, or light switch positions.
    • Temporal Indicators: Check date and time markers such as uncollected mail, product expiration dates, and rotten food.
    • Specific Evidence Interpretation Exemplar: Items observed during scene walkthroughs may include physical containers, such as Soft Best Mari Youn LA Nasal Decongestant PE 1000m1000\text{m}.

  • Walkthrough Outcomes and Operational Decisions

    • Core Objective: Answer the primary question: "What is the most effective way to process the scene?"
    • Task Prioritization: Identify high-priority physical areas and divide tasks among personnel.
    • Tool & Test Selection: Determine the specific field tools, presumptive tests, and equipment required.
    • Search Pattern Selection: Choose the appropriate search method to locate all physical evidence.
    • Specialist Requests: Determine if external specialists (e.g., bloodstain pattern analysts, forensic entomologists) are required on scene.
    • Boundary Refinement: Decide whether to alter initial physical scene boundaries.

Crime Scene Documentation Methods

  • Primary Types of Documentation

    • Logs
    • Notes
    • Photography
    • Sketches
    • Videography

  • Documentation Logs

    • Crime Scene Entry Log Form:
      • Tracks all personnel entering and exiting the scene.
      • Header information required: Agency or Group name, Incident Number (Incident #\text{Incident \#}), and Location.
      • Required column fields: Name & Title, Agency, Location, Initials, Date/Time In, Date/Time Out, and Reason for Entering.
      • Security Rule: Officers assigned to maintain scene security must log in and out on the sheet, stating their reason for entry as "Log Officer".
    • Evidence Recovery Log Form:
      • Tracks all physical evidence removed from the scene.
      • Header information required: Agency name, Incident Number (Incident #\text{Incident \#}).
      • Required column fields: Item Number (Item #\text{Item \#}), Recovered By, Description, Initials, and Date/Time.
      • Validation Rule: Evidence log officers must sign and date the log directly after the last item number entry is recorded.

  • Crime Scene Notes

    • Must explicitly detail WHEN the investigator was present at the scene.
    • Must record WHAT specific actions the investigator took.
    • Must record WHAT physical observations were made.
    • Must document WHO the investigator worked with.
    • Must be written in real-time directly at the scene.

  • Crime Scene Photography

    • Importance: Recognized as the single most important documentation tool in forensic operations.
    • Technical Criteria:
      • Adequate image size.
      • Appropriate focus.
      • Adequate lighting and illumination.
    • Primary Objective: Accurately depict and illustrate the entire scene.
    • Distance Categories:
      • Long Range Photos: Taken from a distance greater than 3 m3\text{ m} to 5 m5\text{ m}; designed to capture overall scene context.
      • Mid Range Photos: Taken from a distance of 1 m1\text{ m} to 3 m3\text{ m}; captures spatial relationships among a few pieces of evidence or a isolated section of the scene.
      • Close-Up Photos: Taken from a distance of less than 1 m1\text{ m}; focuses strictly on the physical details of a single evidence item.
      • Examination Quality Photos: Macro- or extreme close-up photos containing enough fine detail for individualization; always shot perpendicular to the object using physical measurement scales (e.g., markers 77, 88, 99).

  • Crime Scene Sketching and Computer-Aided Drawing (CAD)

    • Purpose: Graphically depicts the precise spatial relationships between evidence items.
    • Advantages:
      • Eliminates graphic visual gore.
      • Not obstructed by physical line-of-sight constraints.
      • Simplifies complex three-dimensional scenes into a clear, single two-dimensional image.
    • Sketch Types & Details:
      • Rough hand sketches and floor plans capture raw field dimensions (e.g., perimeters measured at 75′75' and 27′27').
      • Common contextual items mapped in sketches include structural features and furniture (e.g., Furnace, HW, Storage, Table, Pool Table, Coffee Table, Dresser, Window, Door, Rug, Bed, DVR, DVD Player, Book).
      • Victim positioning is mapped (e.g., Victim #1\text{\#1}: Robert Pruitt; Victim #2\text{\#2}: ID unknown).
      • Numbered item legends explicitly map items to spatial coordinates (e.g., Legend Item 11: Panties; Item 22: Broken wine glass; Item 33: Red stain; Item 44: Used condom).
      • Sketch Metadata Requirements: Case Number (e.g., Case # 2014, 01637\text{\# 2014, 01637}), Artist Name (e.g., Artist Rachel Mohr), Location Address (e.g., 14862 Eastvale Rd), Date and Time (e.g., 7/14/2014, 10:50 PM).
    • CAD (Computer Aided Drawing): Software used to translate rough field sketches into clean, publication-grade digital renderings for court presentation.

  • Videography

    • Serves as the best visual demonstration for physical movement paths through a scene.
    • Rarely matches the high resolution of digital still photography.
    • Must begin with a clear introductory overview segment.
    • Audio Protocol: Must be recorded with no microphone active and contain no audio narration.

Crime Scene Search Techniques

  • Search Methodologies: Pros, Cons, and Applications

    • Zone Search:
      • Pros: Works well for a solo searcher; adapts easily to small or irregularly shaped areas.
      • Cons: Scene must be easily divisible into distinct zones; can be highly inefficient if poorly planned.
    • Line / Strip Search:
      • Pros: Ideal for searching large outdoor expanses; effective across irregular terrain.
      • Cons: Requires multiple search personnel for optimal performance; requires at least one clearly defined physical starting boundary.
    • Grid Search:
      • Pros: Exceptionally thorough double-coverage search pattern.
      • Cons: Requires multiple searchers; highly time-consuming; requires distinct exterior boundaries; awkward to execute in confined indoor spaces.
    • Spiral Search:
      • Pros: Easy for a single investigator to execute solo; highly effective at identifying entry and exit paths leading to a focal point.
      • Cons: Awkward to execute within indoor structures; difficult to maintain a geometrically perfect spiral pattern.
    • Wheel / Ray Search:
      • Searchers move outward from a central point along radial paths (or inward toward a central point).
    • Link Search Method:
      • Does not rely on geometric patterns; searchers follow logical physical connections between individual items of evidence based on scene context and preliminary facts.

  • Evidence Detection Assistance Tools

    • Alternative Light Source (ALS):
      • High-energy light source that causes specific biological and non-biological materials to fluoresce/glow.
      • Detects biological stains, broken glass, hairs, and synthetic/natural fibers.
      • Requires barrier optics or goggles to filter out background light.
    • Color Testing:
      • Field chemical reagents (e.g., NARK II Inc) allowing rapid presumptive identification of unknown chemical substances.
      • Exhibits significantly higher error rates (false positives/negatives) compared to laboratory analysis.
    • Fingerprint Dusting:
      • Application of specialized powders to physical surfaces to reveal otherwise invisible (latent) friction ridge fingerprints.

  • Marking and Documenting Located Evidence

    • Mark every physical item that could reasonably constitute evidence using visible numerical markers (e.g., markers 11, 22, 33, 44, 55, 66, CO\text{CO}).
    • Photograph evidence markers in place to preserve complete scene context prior to collection.

Evidence Collection, Handling, and Packaging

  • General Evidence Collection Principles

    • Primary Goal: Preserve physical evidence completely intact without introducing cross-contamination.
    • Personal Protective Equipment (PPE\text{PPE}): Handlers must wear clean gloves, use sterilized forceps, or wear face masks during collection.
    • Field Testing: Perform field tests and document all test outcomes prior to final packaging.
    • Individual Packaging: Every item must be packaged separately in its own appropriate container.

  • Presumptive Testing and Documentation Results

    • Apply presumptive chemical tests as necessary (e.g., Phenolphthalein test for presumptive presence of blood on suspected stains).
    • Control Standard: Always test both the suspected visible stain and an adjacent unstained substrate control area.
    • Photograph colorimetric test results immediately and record detailed findings in written notes.
    • Photograph negative findings, including areas yielding negative fingerprint dusting results.

  • Evidence Packaging Selection Standards

    • Safety: Protects handling personnel from physical harm or biohazard exposure.
    • Physical Integrity: Protects contents from physical fracture, compression, or structural damage.
    • Containment: Protects against fluid leakage or particulate loss.
    • Fit: Sized to fit the evidence item comfortably without force.
    • Cost-Efficiency: Uses the cheapest available packaging that fully satisfies all safety and preservation requirements.

  • Biological Evidence Processing Rules

    • Types of Biological Fluids: Saliva, Semen, Blood, Urine, Feces, Vomitus.
    • Environmental Degradation Hazards: Extremely susceptible to destruction by Bacteria, Fungus, and Ultraviolet (UV\text{UV}) Light.
    • Storage Environment Rules:
      • Keep it dry.
      • Keep it dark.
      • Keep it cold.
    • Specific Packaging Procedures:
      • Individual Liquid/Wet Stains: Swab using sterile cotton swabs, allow swabs to air dry completely, and package in a breathable paper box.
      • Wet Stains on Fabric/Garments: Wrap the wet garment in plain paper, place inside a paper bag, and allow to air dry completely flat.
      • Dry Stains on Fabric/Garments: Package directly into breathable paper containers.

  • Special Evidence Safe Packaging Protocols

    • Documents: Enclose in flat paper envelopes reinforced with rigid cardboard inserts to prevent bending or creasing.
    • Firearms, Knives & Other Weapons: Securely zip-tied inside heavy-duty cardboard boxes to prevent movement.
    • Ammunition: Store in padded or wrapped containers to isolate cartridges.
    • Hairs & Fibers: Package exclusively in paper containers using paper fold bindles (never store in plastic bags due to static electricity).
    • Burnt Evidence / Arson Samples: Store in clean, sealed metal paint cans or airtight sealed glass jars to trap volatile chemical accelerant vapors.

Final Scene Assessment

  • Conduct a comprehensive final walk-through to ensure all physical scene areas have been thoroughly searched.
  • Cross-check all recovery logs against actual physical evidence packages to verify total accountability.
  • Finalize the official inventory of all physical items collected.
  • Assign remaining final duties and cleanup tasks to personnel.
  • Clean up operational waste generated during the investigation.
  • Identify and formally report any remaining environmental or physical hazards.
  • Formally release scene custody back to the property owner or appropriate authority.

Chain of Custody Protocols

  • Definition and Core Purpose

    • Chronological documentation tracking the continuous seizure, control, transfer, analysis, and final disposition of physical evidence.
    • Fundamental Custody Rule: An identifiable individual person must ALWAYS maintain secure, physical custody of every piece of evidence at all times.

  • Custody Transfer Example Sequence

    • An evidence item moves sequentially through identifiable custodians:         Suspect→CSI Leela→Evidence Clerk Zoidberg→Technician Fry→Evidence Clerk Zoidberg→Analyst Farnsworth→Evidence Clerk Zoidberg→Attorney Rodriguez→Court\text{Suspect} \rightarrow \text{CSI Leela} \rightarrow \text{Evidence Clerk Zoidberg} \rightarrow \text{Technician Fry} \rightarrow \text{Evidence Clerk Zoidberg} \rightarrow \text{Analyst Farnsworth} \rightarrow \text{Evidence Clerk Zoidberg} \rightarrow \text{Attorney Rodriguez} \rightarrow \text{Court}

  • Foundational Packaging Information and Labeling

    • Required Core Fields:
      • Case Number (Case No.\text{Case No.})
      • Item Number (Item No.\text{Item No.})
      • Description of Enclosed Evidence
      • Date and Time of Collection
      • Identity of Collector (Name and Badge Number)
      • Tamper-proof Seal placed across container opening
    • Extended Information Fields on Bags and Forms:
      • Submitting Agency
      • Type of Offense
      • Location Where Collected
      • Victim's Full Name
      • Suspect's Full Name
      • Bag Sealed By Signature Block (including From, To, Date, and Badge Number)
    • Implementation Formats: Information may be printed directly on packaging, applied via adhesive labels, recorded on separate physical forms, or tracked electronically using Laboratory Information Management System (LIMS\text{LIMS}) barcodes.

  • Secure Physical Custody Storage Methods

    • Locked storage cabinets or drawers.
    • Individual secured evidence lockers.
    • Locked evidence storage vaults/rooms managed by designated evidence control officers (e.g., Reno, NV Evidence Control Facility).

  • Consequences of Chain of Custody Failure

    • The physical evidence becomes legally inadmissible in court proceedings.
    • The individual officer or investigator responsible for the breach may face employment termination.
    • The crime laboratory involved may face official sanctions or loss of accreditation.
    • The professional reputation of all involved agencies and personnel suffers severe harm.

  • Final Evidence Disposition Options

    • Permanent retention by the police department.
    • Return of property to its lawful owner.
    • Legal forfeiture.
    • Complete destruction of the item.

Summary Evaluation of Crime Scene Protocols

  • Positive Structural Aspects ("The Good")

    • Standardized processes and operational procedures exist to locate and preserve distinct evidence categories.
    • Protocols ensure investigators can perform scene duties safely.
    • Investigators maintain heightened awareness regarding contamination vectors.
    • Rigorous policies governing scene documentation and chain of custody ensure fairer judicial outcomes.

  • Negative Systemic Challenges ("The Bad")

    • Errors occurring at the crime scene due to ambient background noise or initial mis-identification often cannot be rectified later.
    • Large or complex crime scenes create conflicting, overlapping tasks that complicate management.
    • Not all physical evidence present at a scene will successfully be located or recovered.
    • Investigators do not always strictly maintain required standards for chain of custody protocols.