Ch. 2 Crime Scene Investigation Notes
Crime Scene Investigation
Abstract
The crime scene is central to forensic science; its careful processing is paramount.
Crime scene processing is irreversible.
Standard operating procedures and protocols guide investigators, but training, experience, and education are crucial for adapting to unique scenes.
Keywords: Artifact, Bloodborne pathogens, Context, Crime scene investigator (CSI), Datum, Feature, Material safety data sheet (MSDS), Organic or environmental remains, Provenance, Universal precautions
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 an event or item.
Crime scene investigator (CSI): Personnel trained to process crime scenes.
Datum: A fixed reference point for measurements.
Feature: A non-portable artifact (e.g., fire pit, house).
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 3D space.
Universal precautions: Treating all human blood and body fluids as potentially infectious.
Introduction
Crime scenes transform ordinary items into evidence.
Real crime scene processing is more complex than depicted in media.
The crime scene is the foundation for all subsequent forensic analysis.
Proper crime scene processing is critical to avoid mistakes that can affect an entire case.
Many agencies employ specially trained personnel for crime scene processing.
Processing a crime scene is a "careful destruction" method, meaning that actions cannot be undone.
Standard operating procedures guide CSIs in evidence collection, documentation, and transmittal to the laboratory.
Of Artifacts and Evidence
Archaeological excavations and crime scene processing both aim to collect and record information/evidence.
Both processes are irreversible.
Documenting the context of items is crucial for reconstruction.
Technical terms borrowed from archaeology:
Datum: A fixed reference point for 3D measurements; should be permanent (e.g., light switch, tree).
Artifact: A human-made or modified portable object.
Feature: A non-portable artifact.
Organic or environmental remains: Natural remnants indicating human activity (e.g., bones, plants).
Archaeological site: A place where artifacts, features, and organic remains are found together.
Matrix: The material surrounding a find
Provenance: The origin and derivation of an item in three-dimensional space, in relation to a datum and other items.
Context includes the immediate matrix, provenience, and association with other finds.
Archaeological methods can enhance forensic skills.
Evidence is information (testimony, documents, objects) that makes a fact more or less likely.
This chapter focuses on physical evidence.
Crime Scene Investigation
Forensic science deals with the "unlikely and the unusual."
Each crime scene is unique.
Protocols may be adapted based on the circumstances of the crime scene.
CSIs must follow protocols but also be flexible and creative.
First on the Scene
Initial actions are critical to the success of the 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 interpretations.
The primary task of the First Officer (FO) is to secure the scene and prevent destruction or alteration of context.
FO's duties include:
Detaining potential suspects.
Rendering medical assistance.
Preserving the scene.
Preventing others from altering the scene.
Approach the scene carefully and thoughtfully.
Prevent further entry until additional staff arrive.
Define and evaluate the scene to develop an overview and plan of action.
Plan of Action
Obtain a search warrant if necessary.
Discuss the search with personnel before arriving.
Establish a command station away from the scene but within the secured perimeter.
Assign personnel tasks (scene security, evidence log, survey, description, photography, sketch, evidence custodian).
Ensure communication between agencies (medical examiners, lab personnel, EMTs, attorneys).
Think ahead to resolve issues and prevent administrative backlash.
Prepare paperwork to document the search before searching.
Agree on terminology.
Arrange for protective clothing, communication, lighting, shelter, transportation, equipment, food, water, medical assistance, and security.
Use multiple shifts/teams for prolonged searches and develop a transfer mechanism for paperwork and responsibility.
Secure the Scene, Secure the Item
Take control of the scene immediately.
Determine the extent of protection already in place.
Talk to personnel knowledgeable about the original condition.
Keep unauthorized personnel out and record who enters and leaves, including superiors.
Rename the sign-in/sign-out form to "subpoena contact form".
Take copious notes: document who did what and when.
Corroborate notes between supervisors and employees.
Secure the scene to prevent distortion, as even the perception of an unsecured scene can be critiqued in court.
Documentation should demonstrate the quality of work and proper collection/security of items.
Preliminary Survey
The survey is an organizational stage to plan the search.
Cautiously walk the scene with professionalism and calm.
Take preliminary photographs to establish the scene and search area.
Expand the perimeter if needed.
Note special "problem" areas.
Take extensive notes on the scene, conditions, and personnel tasks.
Evaluate physical evidence collection requirements and ensure sufficient supplies.
Focus on fragile evidence first, then robust evidence.
Consider all possible evidence, not just within specialties.
Search accessible areas first, then out-of-the-way locations.
Look for hidden items, secret compartments, and false fronts.
Evaluate whether evidence appears moved or altered.
Designate items as evidence, then record and collect them.
The evidence listing is a "reverse shopping list."
The scene may be contrived.
Photography
Begin photography as soon as possible.
The photographic log documents all photos with descriptions and locations.
Collect a progression of establishing, medium, and close-up views.
Take multiple views (eye level, top, side, bottom).
Start with the most fragile areas.
Document the process itself.
Take photographs before evidence is recovered.
Take photographs with and without a scale, including photographer's initials and date on the scale.
Use scales to reproduce photos at defined scales.
Photograph the crime scene in an overlapping series using a wide-angle lens (50 mm lenses are standard).
Take many photographs to aid in reconstruction.
Establish the location of the scene with overall photos, including landmarks, with 360° coverage.
Photograph entrances and exits.
Obtain prior photographs, blueprints, or maps if available.
Sketch
Crime scene sketches contain crucial elements for reconstruction: distances, angles, time, temperature.
Sketches complement photographs.
Locate items of evidence on the sketch to help establish locations.
Sketches are quantitative but not normally drawn to scale.
Include measurements and details for a drawn-to-scale diagram.
A sketch should include:
The case identifier
Date, time, and location
Weather and lighting conditions
Identity and assignments of personnel
Dimensions of rooms, 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 form documents the movement of evidence from the time it is obtained to the time it is presented in court.
Inaccuracies or gaps in the chain of custody can render evidence useless.
Document each exchange of an item: where, who had control, when, and potential tampering.
The chain of custody is essential for forensic science results to be admissible in court.
Crime Scene Search and Evidence Collection
The crime scene search should be methodical and performed in a specific pattern (spiral, strip/lane, grid).
Adhering to a pattern prevents random bagging and tagging.
Measure the location of evidence by two or more measurements from non-movable items (doors, walls).
Take measurements from perpendicular angles for triangulation.
Mark evidence locations on the sketch and complete the evidence log.
Use one person as evidence custodian for organization.
Two people should observe evidence in place, during recovery, and being marked for identification.
Use tags or mark directly on the evidence.
Wear gloves to avoid leaving fingerprints, be aware that after about 30 min, it is possible to leave fingerprints through latex gloves!
Avoid excessive handling of evidence after recovery.
Seal all evidence packages with tamper-evident tape at the crime scene.
Collect known standards from the scene (fiber samples, glass).
Monitor paperwork, packaging, and information for errors, clarity, and consistency.
Measurements
Simple geometry helps locate and reconstruct items in a sketch.
Take measurements from at least two locations for checking distances and triangulating untaken measurements.
Triangulation is finding a distance 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 surveying: accurately determining the position of points and distances between them.
Large crime scenes may require standard surveying.
Final Survey
Review all aspects of the search.
Discuss the search and ask questions.
Read over the paperwork for completeness.
Take photographs of the scene showing the final condition.
Secure all evidence and retrieve all equipment.
Conduct a final walk-through with at least two people from different agencies as a check on completeness.
Document the release of the crime scene with time, date, and to whom it was released.
Ensure other specialists (bloodstain pattern analyst, medical examiner) have access before release.
Re-entry may require a warrant, so release only when satisfied that the scene was searched correctly and completely.
Submission of Evidence to the Laboratory
Evidence may be submitted by laboratory personnel, CSIs, or law enforcement officers.
Fill out a form or write a letter detailing what is submitted, under what criminal circumstances, who is submitting the items, and what laboratory examinations are requested.
Safety
Walking into a crime scene is one of the most hazardous activities for forensic scientists or CSIs.
Chemical and biological threats abound, along with other dangers.
Crime scene personnel often have little foreknowledge of potential hazards.
Intentional use of chemical/biological agents or explosives by terrorists increases safety concerns.
Increased awareness of bloodborne pathogens (BBPs) and other pathogens has heightened personal protection measures.
Precautions are mandated by individual agencies' protocols and federal laws/regulations.
Sources and Forms of Dangerous Materials
Inhalation: Airborne contaminants (dust, aerosol, smoke, vapor, gas, fume) can cause immediate respiratory irritation or chronic damage to organs. Some inhalants may be invisible!
Skin Contact: Physical collection of items can lead to skin contact. Direct effects: irritation or trauma. Systemic effects: dizziness, tremors, nausea, organ damage, shock. Use gloves, safety glasses, goggles, face shields, and protective clothing.
Ingestion: Less common, but corrosive materials can damage the mouth, throat, and digestive tract. Toxic chemicals can be absorbed through the stomach and intestines. Wash hands, and do not bring food, drink, or cigarettes into contaminated areas.
Injection: Needlesticks and cuts from contaminated objects can inject contaminants directly into the bloodstream. Exercise extreme caution when handling sharp objects.
Universal Precautions
OSHA issued regulations regarding occupational exposure to BBPs in December 1991.
Occupations at risk include law enforcement, emergency response, and forensic laboratory personnel (Title 29 CFR, 1910.1030).
Fundamental to the BBP Standard is the primary concept for infection control called Universal Precautions.
Treat all human blood, body fluids, or other potentially infectious materials as if they are infected with diseases such as hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV).
Protective measures (Title 29 CFR, 1991):
Use barrier protection (disposable gloves, coveralls, shoe covers).
Change gloves when torn or punctured.
Wear eye and face protection against splashes.
Place contaminated sharps in puncture-resistant containers with a BIOHAZARD label; do not bend, recap, or remove needles.
Prohibit eating, drinking, smoking, or applying cosmetics where infectious materials are present.
Wash hands after removing gloves or PPE; remove PPE in a way that avoids contamination.
Decontaminate equipment after use with a solution of household bleach diluted 1:10, 70% isopropyl alcohol, or other disinfectant; allow sufficient contact time.
Prudent work practices and proper packaging also reduce exposure.
Chemical Safety
Health and safety hazards can be encountered (see Table 2.1).
Awareness comes from the information contained in a Material Safety Data Sheet (MSDS) and appropriate training.
MSDS provides information on hazards, safe handling, and responsible use of hazardous materials.
Chemical Safety Hazards
Flammable or combustible materials: Gasoline, acetone, ether ignite easily when exposed to air and an ignition source.
Explosive materials: Nitroglycerine and nitroglycerine-based dynamite, deteriorate to become chemically unstable/sensitive to heat, shock, and friction.
Pyrophoric materials: Phosphorus, sodium, barium ignite in air temperatures less than () without an external ignition source.
Oxidizers: Nitrates, hydrogen peroxide, concentrated sulfuric acid promote combustion. Avoid storage with flammable/combustible materials.
Be aware of hazardous materials, disposal techniques, personal protection, packaging/shipping procedures, and emergency preparedness.
Personal Protective Equipment
Hand protection should be selected based on the material being handled and its hazards. Detailed information can be obtained from the manufacturer.
Nitrile gloves: Protection from acids, alkaline solutions, hydraulic fluid, photographic solutions, fuels, aromatics, and some solvents; cut resistant.
Neoprene gloves: Protection from acids, solvents, alkalies, bases, and most refrigerants.
Polyvinyl chloride: 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.
Inspect gloves for holes before use. Remove rings/jewelry.
Double gloving may be necessary or useful.
Replace gloves if torn or punctured. Remove by peeling off inside out, and discard in designated containers; do not reuse.
Eye protection: Safety glasses and goggles for biological, chemical, and radioactive materials. Face shields for splashing/flying debris (must be worn with safety glasses).
Foot protection: Shoes that completely cover and protect the foot (no sandals or sneakers!). Protective footwear when there is a danger of foot injuries or electrical hazards. Shoe covers can provide protection to shoes and prevent contamination to the perimeter and areas outside the crime scene.
Other protection: Respiratory protection for noxious fumes, protective helmets for structural damage (bombings, fires).
Transporting Hazardous Materials
Title 49 of the Code of Federal Regulations (CFR) codifies specific requirements that must be observed in preparing hazardous materials for shipment by air, highway, rail, or water.
Title 49 CFR 172.101 provides a Hazardous Materials Table that identifies items considered hazardous for the purpose of transportation, special provisions, hazardous materials communications, emergency response information, and training requirements.
Training is required to properly package and ship hazardous materials employing any form of commercial transportation.
Summary
The crime scene is the center of the forensic world.
The importance of a carefully processed crime scene cannot be overstated.
The processing of a crime scene is a one-way street; there is no going back.
Standard operating procedures and protocols guide the CSI, but training, experience, and education all play a role in adapting to each unique crime scene.
Abstract
Crime scene processing is central to forensic science and irreversible.
Standard procedures guide investigators, but adaptability is crucial.
Keywords: Artifact, Bloodborne pathogens, Context, CSI, Datum, Feature, MSDS, Organic remains, Provenance, Universal precautions.
Key Terms
Artifact: Human-made portable object.
Bloodborne pathogens (BBPs): Infectious microorganisms in blood.
Context: Circumstances surrounding an event/item.
Crime scene investigator (CSI): Trained personnel for crime scene processing.
Datum: Fixed reference point for measurements.
Feature: Non-portable artifact.
Material safety data sheet (MSDS): Information on hazardous materials.
Organic/environmental remains: Natural remnants indicating human activity.
Provenance: Origin of an item in 3D space.
Universal precautions: Treat all body fluids as potentially infectious.
Introduction
Crime scenes transform items into evidence.
Real processing is complex.
Proper processing is critical to avoid mistakes.
Standard procedures guide CSIs.
Of Artifacts and Evidence
Archaeological excavations and crime scene processing both collect/record information.
Documenting context is crucial.
Terms from archaeology: Datum, Artifact, Feature, Organic remains, Archaeological site, Matrix, Provenance.
Context includes matrix, provenience, and association.
Evidence is information making a fact more or less likely.
Crime Scene Investigation
Forensic science deals with the "unlikely and the unusual."
Each scene is unique; protocols adapt.
CSIs must be flexible and creative.
First on the Scene
Initial actions are critical.
Crime scenes are static and dynamic.
Context tells the story; disturbed context is problematic.
First Officer (FO) secures the scene.
FO's duties: Detain suspects, assist medically, preserve the scene, prevent alteration.
Plan of Action
Obtain a warrant if needed.
Discuss the search; establish a command station.
Assign tasks: security, evidence log, survey, photography, sketch, custodian.
Ensure communication.
Think ahead; prepare paperwork.
Arrange protective gear, communication, lighting, shelter, etc.
Use multiple shifts/teams.
Secure the Scene, Secure the Item
Take control immediately; determine protection.
Keep unauthorized personnel out; record entries.
Use a "subpoena contact form."
Document everything; corroborate notes.
Secure to prevent distortion.
Documentation demonstrates quality.
Preliminary Survey
Plan the search; walk the scene calmly.
Take preliminary photos; expand the perimeter if needed.
Note problem areas; take extensive notes.
Evaluate evidence collection needs; focus on fragile evidence first.
Consider all possible evidence; search accessible areas first.
Look for hidden items; evaluate alterations.
Designate, record, and collect evidence.
Photography
Begin ASAP; document all photos.
Collect establishing, medium, and close-up views.
Take multiple views; start with fragile areas.
Document the process.
Photograph before recovery; use scales.
Use wide-angle lens; take many photos.
Establish location with overall photos.
Photograph entrances/exits; obtain prior photos/maps.
Sketch
Sketches contain crucial elements: distances, angles, time, temperature.
Sketches complement photos; locate evidence.
Sketches are quantitative, not to scale.
Include case identifier, date, time, location, conditions, personnel, dimensions, distances, and north arrow.
Chain of Custody
Documents evidence movement from collection to court.
Inaccuracies can render evidence useless.
Document each exchange: where, who, when, tampering.
Essential for admissibility.
Crime Scene Search and Evidence Collection
Methodical search pattern (spiral, strip/lane, grid).
Measure evidence location from non-movable items.
Take measurements from perpendicular angles.
Mark locations on sketch; complete evidence log.
Use an evidence custodian; have two observers.
Use tags or mark evidence directly.
Wear gloves; avoid excessive handling.
Seal packages with tamper-evident tape.
Collect known standards; monitor paperwork.
Measurements
Geometry helps locate items.
Take measurements from at least two locations.
Triangulation finds distance by calculating triangle sides.
Measuring is surveying; large scenes require standard surveying.
Final Survey
Review all aspects; discuss the search.
Read over paperwork; take final condition photos.
Secure evidence; retrieve equipment.
Conduct a final walk-through; document the release with time, date, and recipient.
Ensure specialists have access; re-entry may require a warrant.
Submission of Evidence to the Laboratory
Submitted by lab personnel, CSIs, or officers.
Include a form detailing submission circumstances and requested examinations.
Safety
Crime scenes are hazardous.
Chemical, biological, and other threats exist.
Personnel have limited foreknowledge.
Intentional use of agents increases concerns.
Awareness of pathogens has heightened protection.
Precautions are mandated.
Sources and Forms of Dangerous Materials
Inhalation: Airborne contaminants can cause irritation or damage.
Skin Contact: Physical collection can lead to irritation or systemic effects.
Ingestion: Corrosive materials can damage the digestive tract; toxic chemicals can be absorbed.
Injection: Needlesticks can inject contaminants into the bloodstream.
Universal Precautions
Treat all fluids as infected with HBV, HCV, and HIV.
Protective measures: barrier protection, change gloves, eye/face protection, puncture-resistant containers, prohibit eating/drinking/smoking, wash hands, decontaminate equipment.
Chemical Safety
Awareness from MSDS and training.
Chemical Safety Hazards
Flammable/combustible: Gasoline, acetone ignite easily.
Explosive: Nitroglycerine is unstable.
Pyrophoric: Phosphorus ignites in air.
Oxidizers: Nitrates promote combustion.
Personal Protective Equipment
Hand protection: Nitrile, Neoprene, Polyvinyl chloride, Latex gloves.
Eye protection: Safety glasses, goggles, face shields.
Foot protection: Shoes that cover the foot; shoe covers.
Other protection: Respiratory protection, helmets.
Transporting Hazardous Materials
Title 49 CFR codifies requirements for shipping hazardous materials.
Training is required.
Summary
Crime scene is central.
Careful processing is vital and irreversible.
Procedures guide CSIs, but training and experience are essential.