Chapter 4: Physical Evidence Collection

Instructor O'Neil

  • Focus on Crime Scene/Forensic Science Technology, emphasizing practical application and scientific principles in evidence management.

Objectives

  • Understanding key principles in collecting physical evidence, including legal considerations, proper handling techniques, packaging, documentation, and preservation to ensure admissibility in court.

Consideration

  • Two Major Areas of Consideration in Evidence Collection:

    • Legal

      • 4th Amendment: Protects individuals against unreasonable searches and seizures by government agents. Generally, a warrant based on probable cause is required for a lawful search.

      • Search Warrant: A legal document issued by a judge that authorizes law enforcement officers to conduct a search of a person, location, or vehicle for specific evidence of a crime. It must specify the place to be searched and the items to be seized.

      • Prosecutor's Office Consultation: Should be involved in the evidence collection process, especially for complex cases or uncertain legal grounds, to ensure legal compliance and enhance the admissibility of evidence.

      • Exceptions to Warrant Requirement:

        • Lawful Arrest (Search Incident to Arrest): Allows for protective measures during evidence collection, permitting officers to search the person arrested and the area within the arrestee's immediate control to prevent the destruction of evidence or ensure officer safety.

        • Plain View: Evidence that is clearly visible to an officer who is lawfully in a position to see it can be seized without a warrant, provided its incriminating nature is immediately apparent.

        • Consent: Individuals can voluntarily give permission for searches without a warrant. This consent must be freely given and by someone with the authority to grant it.

        • Vehicle Search (Automobile Exception): Can be conducted if there’s probable cause to believe that a crime has occurred or that a vehicle contains illegal contraband or evidence related to a crime. The scope of the search extends to any area where the evidence might reasonably be found.

        • Exigent Circumstances (Destruction of Critical Evidence): Immediate action may be taken if there is an objectively reasonable basis to believe that evidence is about to be destroyed, a suspect will escape, or there is an immediate threat to the public or officers.

    • Legal Implications: Any evidence obtained improperly, in violation of constitutional rights or established legal procedures, may create reasonable doubt in the case and can be deemed inadmissible in court under the doctrine of fruit of the poisonous tree. This doctrine states that evidence later discovered and derived from an illegally obtained initial discovery is also considered inadmissible.

Collection of Evidence

  • Amount to Collect: It is advisable to collect more evidence rather than less. Over-collection allows for comparative analysis, re-testing, and provides a buffer against accidental loss or degradation of some samples, while ensuring all potential leads are explored.

  • Returning to Crime Scene: Often necessary for renewed inspection and analysis, especially if new information arises, initial search was incomplete, or specific types of evidence (e.g., latent prints) require advanced processing.

  • Comparison: Known specimens (also called standards, exemplars, or control samples) should be compared to unknown samples found at the crime scene. This comparison helps establish common origin or characteristics.

  • Blank Samples: Should also be collected from the crime scene, similar substrates, or unused packaging materials for control purposes. These help detect any contamination introduced during collection, storage, or analysis.

  • Handling Practices:

    • Evidence should be handled as little as possible using appropriate personal protective equipment (PPE) like gloves, masks, and coveralls to avoid contamination with foreign DNA, fibers, or fingerprints.

    • Packaging to prevent deterioration, loss, and further contamination is essential immediately upon collection.

  • Drying Cabinets: Utilize specifically designed drying cabinets or secure, well-ventilated areas to store perishable evidence (e.g., blood-soaked clothing, damp biological samples) to prevent mold growth and bacterial degradation.

  • Cross-Contamination: Must actively avoid cross-contamination; always keep unknown samples separate from known items and from each other. Use fresh gloves and instruments for each piece of evidence.

Types of Packaging

  • Assortment of Packaging Materials: Use a variety of materials depending on the evidence type, including paper envelopes, cardboard containers, paper bags, evidence tape, sterile plastic bottles (for non-biological liquids), and specific containers for trace evidence.

  • Avoidance of Plastic Bags: They generally accelerate deterioration and mold growth for biological or damp evidence because they trap moisture, creating an anaerobic environment conducive to bacterial activity.

  • Use Airtight Containers: Specifically for volatile evidence (e.g., gasoline-soaked clothes, accelerants from fire scenes), to prevent evaporation of essential components and preserve fumes for analysis.

  • Specific Guidelines:

    • Burned Debris: Must never be placed in plastic bags or jars if containing potential accelerants, as volatile residues can degrade or evaporate. Instead, use clean, unused paint cans or glass jars with airtight lids.

    • Small Items: Should be double-wrapped (e.g., in a druggist's fold then an evidence bag) for security and to prevent loss or leakage of minute traces.

    • Druggist’s Fold or Gelatin Lifter: Ideal for collecting small traces of evidence like hairs, fibers, or glass fragments. A druggist's fold uses paper to create a secure packet for tiny items.

    • Cardboard Boxes & Zip-Ties: For transporting small to medium, fragile items ensuring they are protected from impact and movement within the package.

    • Sharp Objects: Should be packaged using specific safety measures. Securely affix them to a piece of cardboard within a puncture-resistant container (e.g., rigid plastic tube or box) to prevent injury to handlers and damage to the object.

    • Firearms: Require special attention; they must be rendered safe (unloaded), secured to prevent movement, and packaged separately in a sturdy box, often marked with biohazard stickers if biological fluids are present.

Microscopic or Trace Evidence

  • Consultation with Crime Lab: Essential for collecting trace evidence (e.g., hairs, fibers, paint chips, glass fragments) to ensure appropriate collection methods are used, minimizing loss and maximizing analytical value.

  • Techniques for Collection:

    • Vacuuming: Used for collecting trace evidence from large areas or irregular surfaces, where individual picking is impractical.

    • Shaking: Useful for dislodging particles from clothing or textiles over a clean sheet of paper.

    • Sweeping: For collecting larger trace evidence particles from hard surfaces.

    • Picking: Using tweezers or gloved fingers for visible, individual items of trace evidence.

    • Using Plastic Tape or Lint Rollers: For lifting hairs, fibers, or other small particulates from surfaces, carefully adhering the tape to a clean backing sheet.

Collection Process of Evidence

  • Order of Collection: Depends on the type of case and circumstances, but generally, the most fragile evidence (e.g., latent fingerprints, DNA, impressions) must be collected first to prevent accidental damage or destruction.

  • Detailed Descriptions Required: Describe evidence meticulously to prevent breakage, spoilage, or contamination. This includes precise location, condition, and any unique characteristics.

    • Bottles & Glass with Liquid: Must not be packaged with other evidence to avoid chemical interaction, spills, or contamination if breakage occurs.

    • Styrofoam: Can be used as a cushion in packaging fragile items to absorb shock during transport.

    • Marked Identifiers: Should be clearly written on the container or tag for identification, including case number, item number, date, time, and collecting officer's initials.

    • Use of Absorbent Cotton: For pills or other small, delicate items to prevent breakage or crushing during transport within a vial or container.

    • Tamper-Proof Evidence Tape: Required for evidence security, applied across all openings of the package to indicate if any unauthorized access has occurred since packaging.

Example of Detailed Descriptions

  • Specifics of Evidence Example:

    • 9 mm casing in living room: Provide specifics, e.g., "9 mm S&W casing, fired, located in living room, approximately 2 feet NW of the front left leg of the couch, near area denoted by PIN 3 on scene diagram."

    • Suspect Clothing: E.g., "White t-shirt, size large, from John Smith (DOB 4/3/89), with apparent dried dark reddish-brown stains consistent with blood, collected from suspect at time of arrest on (date/time)."

Chain of Custody

  • Requirement: Courts necessitate proof that the evidence collected is the same as that submitted to court (integrity of evidence). This unbroken record is crucial for admissibility and to demonstrate that the evidence has not been tampered with.

  • Documentation Necessary:

    • Who had contact with the evidence: Every individual who touched or took possession of the evidence must be recorded.

    • Date & Time of contact: Precise timestamps for each transfer or handling event.

    • Under what circumstances evidence was handled: Details on the purpose of handling (e.g., transportation, analysis, storage, examination).

    • What changes occurred to the evidence: Documentation of any modifications, sampling, or repackaging as a result of forensic procedures.

    • Essential for locating evidence years later, establishing its authenticity, and defending against challenges of tampering.

  • Reports, Logs & Barcode System: Critical tools for maintaining an accurate, transparent, and defensible chain of custody. Barcode systems provide efficient and accurate tracking of evidence movement.

Preservation

  • Methods of Preservation: Encompasses various handling methods and environmental controls to ensure evidence integrity throughout the entire process, including proper packaging, temperature and humidity control during storage, and avoiding exposure to light or contaminants.

Special Crime Scenes

  • Types of Unique Crime Scenes:

    • Underwater Crime Scene: Requires highly trained divers with advanced diver training and specialized equipment to contend with poor visibility, currents, depth, and the delicate recovery of submerged evidence, which can degrade rapidly.

    • HAZMAT (Hazardous Materials) Crime Scene: For chemical and biological hazard scenarios (e.g., toxic spills, unknown substances). Requires specialized training, personal protective equipment (PPE), and adherence to strict safety protocols for collection and processing.

    • Clandestine Drug Laboratories: Specific procedures must be followed due to significant safety concerns including toxic fumes, explosive chemicals, and booby traps. Requires specialized teams (e.g., DEA's Clandestine Lab Teams) to safely dismantle and collect evidence.

    • Mass Disasters: Includes incidents like terrorism, bombings, and major fires, often involving numerous victims, widespread debris, and complex identification challenges. Requires multi-agency coordination and systematic recovery efforts.

    • Federal Agencies Involvement: May be required in such complex situations due to their specialized resources, jurisdiction, or expertise (e.g., FBI for terrorism, DEA for drug labs, EPA for environmental hazards).

Final Thoughts

  • Final Survey of Crime Scene: A meticulous final walk-through, often involving multiple individuals, is crucial to ensure all potential evidence has been collected. A checklist should be used to avoid oversight, and final photographic documentation of the cleared scene is recommended.

  • Releasing Scene: Discusses the irreversible impacts on evidence integrity post-release. Once a scene is released to property owners or the public, it becomes very difficult, if not impossible, to revisit and collect additional evidence, as its integrity will have been compromised.

Activity

  • Engage with the material through practical applications or case studies to reinforce understanding of evidence collection principles.

Images

  • Sources for Visual Aids in Presentation:

    • Search warrant, street sign collection: Obtained from Adobe Stock.

    • Forensic diver: Obtained from UCI Diver.

    • Officer removing crime scene tape: Obtained from Y!sports.

    • Evidence packaging: Obtained from Crime Scene.