Crime Scene Investigation - Comprehensive Notes
Role and Background of the Detective (context for study)
Detective Denny DenHartog is portrayed as an experienced, highly capable officer who also serves as a security presence and mentor.
Career path highlights:
City of Kenosha: security roles, patrol, nightlife incidents, and eventually school-based assignments.
School resource officer covering middle schools, then a high school, then promotion to detective.
As a detective, handled sensitive crimes: crimes against kids, sex crimes, stalking, strangulation, baby deaths (about a dozen cases), then moved to human trafficking.
Retirement from that role and move to Florida; considered US Marshals assignment at a Tampa courthouse, but COVID impacted plans.
Now involved in teaching/crime scene basics in Florida.
Core message: crime scene work is a progression from incident occurrence to evidence collection and courtroom testimony; documentation is essential for legal records.
Key Concepts and Definitions
Crime scene: the location where a crime occurred and where evidence is gathered.
Detective’s authority: once assigned, the detective controls every aspect of the scene and is responsible for all actions taken.
Documentation: everything done at the scene must be documented; reports become legal records used in court later.
Perimeter: controlled zones around the scene. There are two perimeters:
Outer perimeter: broad containment (e.g., blocks around the scene).
Inner perimeter: closer to the evidence, more tightly controlled.
Initial observations: first-pass assessment of what is present, what looks out of place, and what can indicate what happened.
Locard’s principle:
Four signs of evidence (implicit in scene processing): what is near the scene, signs of a struggle, mechanical traces, and environmental details.
Approach vs Getaway: documenting the path into and out of the crime scene helps reconstruct events.
Evidence types: physical items (gun, knife, shell casing, broken objects), trace evidence (DNA, fibers), and digital evidence (cell phones, cameras).
Chain of custody: formal log of who handles evidence, when, and where it is stored; essential for admissibility in court.
Evidence documentation formats: photos, close-ups, video, sketches, and detailed written notes.
Cross-contamination: risk of transferring evidence from one source to another; must be minimized.
Defensive wounds: injuries on a victim’s arms/legs that can indicate a defensive response to an attack; careful language required in reports.
Fourth Amendment context (for students): rights around searches and seizures; seizure vs. search warrants; issues around obtaining digital evidence (e.g., cell phones).
Witness management technique: separating witnesses to prevent collusion and to capture independent statements; “lock them into the story” and sign statements.
Courtroom realities: testimony can be harsh; investigators rely on their notes, photos, and the evidence chain to support their statements.
Crime Scene Lifecycle: Overview
Incident occurs, someone calls police; arriving officers assess safety and scene status.
Detective takes charge, regardless of who else is present (SWAT, chief, etc.).
Tasks for the detective include securing the area, protecting witnesses, and initiating documentation planned to stand up in court years later.
The goal is to collect evidence in a way that preserves integrity and enables the truth to emerge.
Initial Scene Control and Safety
Immediate actions:
Ensure overall safety; treat injured persons; transport as needed with escort to hospital if necessary.
Establish a perimeter (outer and inner) appropriate to the crime type and scale.
Extend or reduce the perimeter based on findings (e.g., shell casings furthest from the shooter, knife closer to the scene).
Perimeter rationale (anecdotal): a misjudged perimeter can lead to missed evidence or suspect escape; proper distance is situation-dependent (e.g., two blocks, ~, ~).
Example anecdote: underestimating perimeter allowed a suspect to slip by 6 blocks, illustrating why a well-defined perimeter is critical.
Documentation and Early Observations
Outer vs. inner perimeter intended to balance evidence protection with accessibility for investigators.
Early observations focus on:
What looks out of place vs. normal items (e.g., water bottles, laptops, donuts, pizza).
Senses: smell (burnt hair smell, fire, chemical odors) and general ambiance.
Visual clues: layout, entry points, potential signs of forced entry, approach and getaway routes.
Core principle: if it doesn’t look right, it isn’t right. A seasoned investigator relies on gut sense (spidey sense) and documentation to verify.
Do not touch items yet; initial documentation begins with photos and notes.
Photography sequence:
Stamp photos of the scene before touching anything.
Use multiple photos: wide shots, mid-range, close-ups; capture approach and getaway points.
If available, video documentation for continuous record of the scene.
Markers and a ruler help convey scale in photos (e.g., measurements for footprints or blood splatter).
Drafting and notes:
Detailed narrative notes describing the scene and each observed item.
Sketches of the scene with measurements when needed.
On-scene processing order:
Observe, photograph, sketch, measure, and note before collecting or moving items.
Evidence handling concepts:
Do not touch evidence with bare hands; wear gloves; use appropriate bags and containers.
Document every item with description, location, and context; label with a unique identifier.
Consider scent and other sensory details that may aid later analysis.
90% likelihood claim (for digital evidence): cell phone data can often be mirrored or recovered on-scene; if not, a search warrant or lab work may be needed. Note: on-scene extraction can be fast for phones; deleted data may still be recoverable with proper forensics.
Witness Handling and Statements
Crucial steps:
Identify and separate all witnesses (e.g., officer Jones, officer Frank).
Interview each witness independently to prevent influence or contamination of statements.
Ask targeted questions to elicit what they observed, when they were there, and why they were present.
Lock witnesses into their stated account by having them sign a written statement; verify consistency later when corroborating with other evidence.
Corroboration:
Cross-verify witness accounts with other witnesses and physical evidence.
Be aware of potential biases or misperceptions; statements may evolve with new information.
Documentation of statements:
Record the witness identity, contact information, and the exact statements; ensure chain of custody for the statements themselves.
Evidence Processing and Documentation
Evidence cataloging steps:
Create a chain of custody log for each item: who handled it, when, where stored, and subsequent transfers.
Move from initial observations to formal evidence collection, ensuring no contamination.
Separate roles among team members: scene evaluator, photographer, evidence collector, and evidence processor.
Evidence collection workflow:
Photograph evidence up close and from multiple angles before touching.
Use evidence markers and rulers for scale where needed.
Measure specific distances (e.g., distance from body to weapon, bloodstain spread, door kick depth).
Record the location of evidence within the scene (e.g., “knife on the eastern wall 2.5 ft from the body”).
Use gloves and appropriate PPE; consider masking strong odors if encountered.
Packaging and labeling:
Place items in appropriate bags; seal and initial the bag; write a clear description on the bag itself.
Example: a doughnut suspected to contain DNA or fentanyl must be documented; initial the bag and log it.
Maintain a detailed inventory of all collected items and their storage location.
On-site vs lab processing:
Some items (e.g., cell phones) may be processed on-site; others require lab analysis, which may take weeks.
Evidence Handling: Types and Techniques
Physical evidence: weapons, shells, broken items, footprints, etc.
Trace evidence: DNA, fibers, residue.
Digital evidence: cell phones, computers, cameras; may require warrants for full extraction.
Forensic limits and cautions:
Cross-contamination risk must be minimized; document when contamination might have occurred.
Some signs may be interpreted as defensive or situational; precise language is necessary in reports (e.g., “defensive wounds” language should be medically corroborated later).
Locard’s principle reminder: any contact between individuals and objects will leave traces; this informs how to seek and interpret evidence.
Handling of Digital Evidence and Fourth Amendment Considerations
Seizure vs search:
Officers can seize a device at the scene if it is part of the crime scene; a search warrant is generally required to examine its contents.
Exceptions exist depending on proximity and immediacy of the threat or ongoing investigation; typically, a warrant is needed to examine the contents.
Fourth Amendment context:
Right to be secure against unreasonable searches and seizures; warrants must be obtained for searches beyond immediate seizure.
In a crime scene context, you can seize items like a phone if they are on the scene and relevant to the incident; a warrant is typically needed for further data extraction.
Practical example:
If the suspect is the primary person near the device and the device is immediately linked to the crime, the officer may seize it and later obtain a search warrant.
Interaction tips for students:
In many situations, it’s beneficial to explain why a seizure is necessary and to seek cooperation; “seize now, warrant later” is not universal and depends on jurisdiction and case specifics.
On-Scene Tools and Techniques: Documentation Toolkit
Photography: wide shots, mid-range, close-ups; be sure to include context and scale with markers.
Video: capture the full sequence of the scene, including approach and getaway routes, lighting conditions, and weather.
Sketching: rough sketch on-site; detailed drawn diagrams can supplement photographs.
Measurements: use rulers or measuring tapes to capture distances between evidence and landmarks (e.g., footprint size, blood spatter reach, door alignment).
Notes: maintain precise, timestamped notes; use a consistent nomenclature for items and locations.
PPE: gloves, booties, masks; consider odor aids or ventilation in high-odor environments; avoid cross-contamination.
Evidence packaging: label, seal, and log each item; place into properly sized evidence bags; record any potential hazards.
Documentation sequence summary:
Initial scene overview
Photograph and video capture
Mark evidence and take close-up shots
Sketch and measure
Separate witnesses and collect statements
Collect and package evidence with chain of custody
Prepare for lab submission and court presentation
Case Examples and Lessons (Anecdotes)
Perimeter misjudgment anecdote:
A detective initially stayed six blocks away, thinking the chase would be safer, but the suspect ran by and the detective nearly missed catching him.
Lesson: better to establish a larger perimeter initially to prevent escape and secure the scene.
Donna Matthews case (stalking escalated to homicide):
Donna, a former suspect, attempted to resolve conflicts violently from Hawaii to Wisconsin; the suspect murdered after returning to the home using fireworks and a gun.
Lesson: even when outside authorities appear unable to intervene directly, investigators must consider threats that exist across distances and jurisdictions; timely, proactive evaluation of restraining orders and credible threats is critical.
Trafficking case and knock-and-talk:
Knocking on a suspect’s door can yield information; leaving a business card can result in future leads; unpredictable outcomes can occur (e.g., a later case linking a business card to an arson).
Courtroom experiences:
Real-life cross-examination is challenging; even well-documented evidence and notes can be challenged by prosecutors and defense attorneys.
Preparedness and consistency of notes are essential to withstand courtroom scrutiny.
Other real-life notes:
Not all cases yield perfect evidence; sometimes only a few items (e.g., witness statement, a photo, and DNA) are sufficient for a conviction.
The investigator’s role includes maintaining composure and relying on the documented process to defend the case in court.
Courtroom Realities and Testimony
Testimony expectations:
Detectors must testify to the work performed at the scene and how evidence was collected and preserved.
If memory fades, investigators should rely on detailed notes and photos to refresh memory.
Second seat role:
In some cases, the detecting officer may sit with the prosecutor to support the case, acting as a primary investigator and witness.
Evidence integration:
Photos, sketches, witness statements, audio, video, and DNA are all pieces of the evidentiary puzzle.
Prosecutors decide the order of presenting evidence; defense may object to admission of certain items; the judge rules on admissibility.
Practical Considerations and Ethical Implications
Officer safety remains the top priority at all times.
Separation of witnesses minimizes collusion risks and preserves the integrity of statements.
Documentation practices must be meticulous to withstand legal scrutiny years later.
Respect for privacy vs. necessity:
Lawful seizure and warrant requirements balance investigative needs with individual rights; this balance influences how digital devices and personal property are handled.
Avoiding bias:
Investigators must follow evidence wherever it leads, even if initial hypotheses seem compelling; be prepared to adjust conclusions as new data emerges.
Public communication considerations:
Avoid public speculation at the scene; preserve the integrity of the investigation and avoid sensationalism.
Quick Reference Terms and Concepts
Perimeter (outer vs inner)
Initial observations
Chain of custody
Locard’s principle:
Defensive wounds
Fourth Amendment (search and seizure)
Seizure vs search warrant
Approach vs getaway
Witness separation and corroboration
Evidence documentation formats: photos, close-ups, video, sketches
PPE (gloves, masks, booties)
Evidence packaging and labeling
On-scene vs lab processing timelines
Courtroom dynamics: order of evidence, admissibility, cross-examination
Study Questions
Why is establishing two perimeters (outer and inner) important on a crime scene?
How does Locard’s principle guide the detective in evidence collection?
What are the key components of a proper chain of custody, and why is it critical for court admissibility?
When and why should witnesses be separated, and how should their statements be documented?
Compare on-scene data collection methods: photos, video, sketches, and measurements. What are the strengths and limitations of each?
How should defensible language be used when describing injuries or forensic findings in reports?
What are the differences between seizing a digital device at the scene and obtaining a search warrant for its data?
Reflect on the Donna Matthews and Kyle Rittenhouse anecdotes. What lessons do these stories provide about investigation challenges and courtroom scrutiny?
List the steps you would take to process a hypothetical scene involving a stabbing and a potential suspect.
How can you minimize cross-contamination at a scene while maximizing evidence collection?