Crime Scene Investigation Notes
Crime Scene Investigation
Abstract
The crime scene is central to forensic science.
A carefully processed crime scene is crucial.
Crime scene processing is irreversible.
Standard operating procedures guide investigators, but training and experience are key.
Keywords
Artifact
Bloodborne pathogens (BBPs)
Context
Crime scene investigator (CSI)
Datum
Feature
Material safety data sheet (MSDS)
Organic or environmental remains
Provenance
Universal precautions
Introduction
Crime scenes transform ordinary items into evidence.
Real crime scene processing is more complex than portrayed in media.
The crime scene is the foundation for forensic analysis.
Mistakes at the crime scene can significantly impact a case.
Specially trained personnel are often employed to process crime scenes.
Crime scene processing is a method of “careful destruction”.
Standard operating procedures guide the CSI.
This chapter focuses on the crime scene itself and evidence collection.
Key Terms
Artifact: A human-made or modified portable object.
Bloodborne pathogens (BBPs): Infectious microorganisms in human blood that can cause disease.
Context: The circumstances and relationships surrounding the evidence.
Crime scene investigator (CSI): Personnel trained to process crime scenes.
Datum: A fixed reference point for measurements at a crime scene.
Feature: A non-portable artifact, such as a fire pit or building.
Material safety data sheet (MSDS): A document providing information on hazardous materials.
Organic or environmental remains: Natural remnants indicating human activity.
Provenance: The origin and derivation of an item in three-dimensional space.
Universal precautions: Safety measures to treat all human blood and body fluids as potentially infectious.
Of Artifacts and Evidence
Archaeological excavation and crime scene processing both involve careful collection and recording.
Both processes are irreversible.
Documenting information and context is crucial.
Datum: A fixed reference point for 3D measurements, preferably permanent.
Artifact: A human-made or modified portable object.
Feature: A non-portable artifact.
Organic or environmental remains: Natural remnants indicating human activity.
An archaeological site contains artifacts, features, and organic remains.
Provenance: The origin and derivation of an item in 3D space, relative to a datum.
Context includes the immediate matrix, provenience, and association with other finds.
Serious crime scene students should study archaeological methods.
Evidence is information used in a legal investigation to make a fact more or less likely.
This chapter primarily discusses physical evidence which are things involved in the commission of a crime.
Crime Scene Investigation
Each crime scene is unique.
Protocols may be adapted based on circumstances.
CSIs must be flexible and creative within accepted limits.
First on the Scene
Initial actions are critical for a successful investigation.
Crime scenes are a mix of static and dynamic information.
Context (relationships between people, places, and things) tells the story.
Disturbed context leads to biased and inaccurate interpretation.
The primary task of the First Officer (FO) is to secure the scene and prevent alteration of context.
Duties of the FO:
Detain potential suspects.
Render medical assistance.
Do not destroy, alter, or add evidence.
Prevent others from doing the same.
The FO should approach the scene carefully.
The lead investigator defines and evaluates the scene.
The initial surveyor develops an overview and plan of action.
Plan of Action
Preparation:
Obtain a search warrant if necessary.
Discuss the search with personnel.
Establish a command station.
Assign personnel tasks.
The person in charge is responsible for scene security, evidence/administrative log, preliminary survey, narrative description, problem resolution, and final decision-making.
The photographer arranges, takes, and coordinates photos and keeps the log.
The sketch preparer coordinates with other documentation methods.
The evidence custodian logs items and ensures proper packaging.
Communication between agencies is crucial.
Think ahead to prevent issues.
Prepare paperwork before searching.
Agree on terminology.
Arrange for protective clothing, communication, lighting, shelter, transportation, equipment, food, water, medical assistance, and security.
Use multiple shifts for prolonged searches and develop paperwork transfer mechanisms.
Secure the Scene, Secure the Item
Take control of the scene immediately.
Determine the extent of scene protection.
Keep out unauthorized personnel and record entries/exits using a "subpoena contact form".
Take copious notes documenting who did what and when.
Contemporaneous notes are essential.
Secure the scene - even the perception of an unsecured scene can cause issues in court.
Photographs, notes and documentation are proof of the quality of work and that each item was properly collected and secured.
Preliminary Survey
The survey is an organizational stage to plan for the search.
Cautiously walk through the scene with professionalism and calm.
Take preliminary photographs to establish the scene and search area.
Expand the perimeter if needed.
Note problem areas and transient evidence.
Document the scene, conditions, and tasks extensively.
Evaluate physical evidence collection requirements.
Ensure enough supplies are available.
Focus on fragile evidence first.
Consider all possible evidence types.
Process easily accessible areas first, then move to less obvious areas.
Look for hidden items and altered evidence.
Designate items as evidence, then record and collect them.
The evidence listing is like a "reverse shopping list".
The scene may be contrived to look like an accident.
Photography
Begin photography as soon as possible.
Maintain a photographic log with descriptions and locations.
Take establishing (overall), medium (within 6 ft), and close-up (within 12 in) views.
Capture multiple views: eye level, top, side, and bottom.
Start with the most fragile areas and document the investigation process.
Take photos before evidence is recovered.
Take photographs with and without a scale, including photographer's details.
Scales allow reproduction at defined ratios.
Use a wide-angle lens and take overlapping photos.
Photograph the exterior scene with landmarks, entrances, and exits.
Obtain prior photographs, blueprints, or maps if available.
Sketch
Sketches include distances, angles, time, and temperature.
Sketches complement photographs.
Evidence locations can be added to the sketch.
Sketches are quantitative but not usually drawn to scale.
Sketches should have measurements for scale diagrams.
A sketch should include:
Case identifier
Date, time, and location
Weather and lighting conditions
Personnel identities and assignments
Room dimensions, furniture, doors, and windows
Distances between objects, persons, bodies, entrances, and exits
An arrow pointing toward magnetic north
Chain of Custody
The chain of custody documents the movement of evidence.
It tracks evidence from collection to court presentation.
Inaccuracies or gaps can render evidence useless.
Document each exchange of an item, no matter how tedious this may be.
This enables forensic science results to be admissible in a courtroom.
Crime Scene Search and Evidence Collection
The Crime scene search must be methodical and follow a specific pattern.
Search Patterns Include:
Spiral
Strip or lane
Grid
Adhering to pattern prevents random collection.
Measure evidence location from two or more fixed points using perpendicular angles for triangulation.
Mark evidence locations on the sketch and evidence log.
An evidence custodian makes collection regular and organized.
Two people should observe evidence in place, during recovery, and marking for identification.
Mark evidence with tags or directly on the evidence if feasible.
Wear gloves to avoid leaving fingerprints.
After 30 min, fingerprints can be left through latex gloves.
Avoid excessive handling of evidence.
Seal evidence packages with tamper-evident tape at the scene.
Collect known standards from the scene.
Check paperwork for errors, clarity, and consistency.
Triangulation uses geometry to find a distance to a point by calculating the length of one side of a triangle, given measurements of angles and sides of the triangle formed by that point and two other reference points.
Measuring a crime scene is a survey.
Large crime scenes may require standard surveying including issues of points (guns, not mountains) and scale (inches, not miles).
Final Survey
Review all aspects of the search.
Discuss the search and ask questions.
Review paperwork for completeness.
Take photographs of the final condition.
Secure all evidence and retrieve equipment.
A final walk-through with two people from different agencies is a must to check for completeness.
Document the time, date, and recipient of scene release.
Other specialists may need access before release.
Re-entry may require a warrant; therefore, the scene should be released only when all personnel are satisfied that the scene was searched correctly and completely.
Submission of Evidence to the Laboratory
Evidence is submitted to the lab by agency personnel, CSIs, or law enforcement.
A form or letter details the submission, circumstances, submitter, and requested examinations.
Safety
Crime scene investigation is hazardous.
Chemical, biological, and physical threats exist.
Crime scene personnel often lack foreknowledge of dangers.
Terrorist use of chemical, biological, or explosive agents increase safety concerns.
The increase in bloodborne pathogens (BBPs) (AIDS and hepatitis) and other pathogens that may be encountered at crime scenes (like the Hantavirus) has made law enforcement and CSIs more aware of personal protection when responding to crime scenes.
Federal laws/regulations from health agencies may apply.
Sources and Forms of Dangerous Materials
Inhalation: Airborne contaminants (dust, aerosol, smoke, vapor, gas, fume) can cause respiratory irritation or systemic damage. Some inhalants may be invisible.
Skin Contact: Can cause irritation, trauma, or systemic effects. The use of appropriate gloves, safety glasses, goggles, face shields, and protective clothing can prevent this contamination.
Ingestion: Can damage the mouth, throat, and digestive tract. Wash hands before eating, drinking, smoking or applying cosmetics. Also, do not bring food, drink or cigarettes into areas where contamination can occur.
Injection: Needlesticks and cuts from contaminated objects can inject contaminants directly into the bloodstream. Extreme caution should be exercised when handling objects with sharp or jagged edges.
Universal Precautions
OSHA regulations require treating all human blood and body fluids as potentially infectious.
Protective measures:
Use barrier protection (gloves, coveralls, shoe covers).
Change gloves when compromised.
Wear eye and face protection.
Place contaminated sharps in puncture-resistant containers with BIOHAZARD labels. Do not bend, recap, remove, or otherwise handle contaminated needles or other sharps.
Prohibit eating, drinking, smoking, or applying cosmetics where human blood, body fluids or other potentially infectious materials are present.
Wash hands after removing PPE.
Decontaminate equipment with bleach (1:10 dilution), 70% isopropyl alcohol, or other disinfectant.
Prudent work practices and proper packaging reduce exposure.
Chemical Safety
Hazards are listed in the Material Safety Data Sheet (MSDS).
MSDS provides information on the hazards of a particular material so that personnel can work safely and responsibly with hazardous materials; MSDSs are typically available through a vendor’s website.
Table 2.1 Numerous Chemical Safety Hazards Can Be Encountered at Crime Scenes
Flammable or combustible materials: Gasoline, acetone, ether, and similar materials ignite easily when exposed to air and an ignition source, such as a spark or flame.
Explosive materials: Over time, some explosive materials, such as nitroglycerine and nitroglycerine-based dynamite, deteriorate to become chemically unstable. In particular, ether will form peroxides around the mouth of the vessel in which it is stored. All explosive materials are sensitive to heat, shock, and friction, which are employed to initiate explosives.
Pyrophoric materials: Phosphorus, sodium, barium, and similar materials can be liquid or solid and can ignite in air temperatures less than 130 ° F (540 °C) without an external ignition source.
Oxidizers: Nitrates, hydrogen peroxide, concentrated sulfuric acid, and similar materials are a class of chemical compounds that readily yield oxygen to promote combustion. Avoid storage with flammable and combustible materials or substances that could rapidly accelerate its decomposition.
When working with chemicals, be aware of hazardous materials, disposal techniques, personal protection, packaging and shipping procedures, and emergency preparedness.
Personal Protective Equipment
Hand Protection: select based on material and hazard. Nitrile gloves provide protection from acids, alkaline solutions, hydraulic fluid, photographic solutions, fuels, aromatics, and some solvents. It is also cut resistant. Neoprene gloves offer protection from acids, solvents, alkalies, bases, and most refrigerants. Polyvinyl chloride is resistant to alkalies, oils, and low concentrations of nitric and chromic acids. Latex or natural rubber gloves resist mild acids, caustic materials, and germicides. Latex will degrade if exposed to gasoline or kerosene and prolonged exposure to excessive heat or direct sunlight. Some people are allergic to latex and can avoid irritation by wearing nitrile or neoprene gloves. Gloves should be inspected for holes, punctures, and tears before use. Rings, jewellery, or other sharp objects that can cause punctures should be removed. Double gloving may be necessary when working with heavily contaminated materials. If a glove is torn or punctured, replace it. Remove disposable gloves by carefully peeling them off by the cuffs, slowly turning them inside out. Discard disposable gloves in designated containers and, it should go without saying, do not reuse them.
Eye Protection: Wear safety glasses and goggles when handling biological, chemical, and radioactive materials. Face shields can offer better protection when there is a potential for splashing or flying debris. Face shields alone are not sufficient eye protection; they must be worn in combination with safety glasses. Contact lens users should wear safety glasses or goggles to protect their eyes. Protective eyewear is available for those with prescription glasses and should be worn over them.
Foot Protection: Shoes that completely cover and protect the foot are essential – no sandals or sneakers! Protective footwear should be used at crime scenes when there is a danger of foot injuries due to falling or rolling objects or to objects piercing the sole and when feet are exposed to electrical hazards. In some situations, shoe covers can provide protection to shoes and prevent contamination to the perimeter and areas outside the crime scene.
Other Protection: Certain crime scenes, such as bombings and clandestine drug laboratories, can produce noxious fumes requiring respiratory protection. In certain crime scenes, such as bombings or fires where structural damage can occur, protective helmets should be worn.
Transporting Hazardous Materials
Title 49 of the Code of Federal Regulations (49 CFR) codifies requirements for shipping hazardous materials by air, highway, rail, or water.
Training is required to properly package and ship hazardous materials using commercial transportation.
Summary
The crime scene is the center of the forensic world.
Standard operating procedures and protocols guide the CSI, but training, experience, and education all play a role in adapting to each unique crime scene.