Investigations | Section 1.4


Fundamentals of Criminal Investigations

Adam J. McKee, Ph.D.


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Section 1.4: The Investigator at the Crime Scene

In most cases, the investigator will arrive at a crime scene after first responders have conducted a preliminary investigation. The investigator will often be the senior officer on the scene and will be the most experienced and best-trained officer on the scene. While the scene is still active, it falls on the investigator to provide leadership to junior officers, review the tasks completed by the first responder, and ultimately to conduct the in-depth investigation.

Crime Scene Debriefing Team

The crime scene debriefing enables law enforcement personnel and other responders to share information regarding particular scene findings prior to releasing the scene. It provides an opportunity for input regarding follow-up investigation, special requests for assistance, and the establishment of post-scene responsibilities.

Establish a crime scene debriefing team, which includes the investigator(s) in charge of the crime scene, other investigators and evidence collection personnel (e.g., photographers, evidence technicians, latent print personnel, specialized personnel, and initial responding officer(s) if still present). Determine what evidence was collected. Discuss preliminary scene findings with team members. Discuss potential technical forensic testing and the sequence of tests to be performed. Initiate any action(s) identified in the discussion that are required to complete the crime scene investigation. Brief person(s) in charge upon completion of assigned crime scene tasks. Establish post-scene responsibilities for law enforcement personnel and other responders. Summary: The crime scene debriefing is the best opportunity for law enforcement personnel and other responders to ensure that the crime scene investigation is complete.

Final Survey of the Crime Scene

A final survey of the crime scene ensures that evidence has been collected and the scene has been processed prior to release. In addition, a systematic review of the scene ensures that evidence, equipment, or materials generated by the investigation are not inadvertently left behind and any dangerous materials or conditions have been reported and addressed.

The investigator in charge should ensure that: Each area identified as part of the crime scene is visually inspected. All evidence collected at the scene is accounted for. All equipment and materials generated by the investigation are removed. Any dangerous materials or conditions are reported and addressed. The crime scene is released in accordance with jurisdictional requirements. Consider taking photographs depicting the condition of the scene at the time. Summary: Conducting a scene walk-through ensures that all evidence has been collected, that materials are not inadvertently left behind, and that any dangerous materials or conditions have been reported and addressed.

Crime Scene Documentation

Compiling reports and other documentation pertaining to the crime scene investigation into a “case file” provides a record of the actions taken and evidence collected at the scene. This documentation allows for an independent review of the work conducted.

The investigator in charge should obtain the following for the crime scene case file:

  • Initial responding officer(s’) documentation.
  • Emergency medical personnel documents.
  • Entry/exit documentation.
  • Photographs/videos.
  • Crime scene sketches/diagrams.
  • Evidence documentation.
  • Other responders’ documentation.
  • Record of consent form or search warrant.
  • Reports such as forensic/technical reports, when they become available.

The above list is limited to crime scene documentation. This should not be considered a comprehensive list of the documents involved in an investigative case file.

This procedure will ensure that reports and other documentation pertaining to the crime scene investigation are compiled into a case file by the investigator in charge of the crime scene and allow for an independent review of the work conducted.

Special Circumstances

While all crime scene investigations pose their individual complexities, some situations may involve atypical crime scene locations or requirements for which law enforcement personnel and other responders should be aware.  Crime scene investigators should adjust their approach to an investigation to warrant specific needs of the investigation which includes:

  • Crime Scenes in correctional and custodial facilities
  • Crime scenes in which the safety of the crime scene investigators must be considered in the approach to the time spent at the scene.

Crime Scene Time Limits

In some instances, deteriorating security or environmental conditions limit the amount of time available for the investigation of the crime scene. While these time limits will not allow for a thorough crime scene investigation to be conducted, the following procedure will maximize the use of the limited time on site. In such circumstances, preparation prior to staging or entry into the crime scene area is paramount. This could include a site survey (e.g., in-person, photographic, photogrammetric or videographic) prior to the team’s arrival at the scene or conducting extensive interviews of any witnesses from the area.

Elements of this preparation and execution are designed to:

  • Determine the time available to remain at the crime scene based on knowledge of time-limiting factors.
  • Determine the most critical objective of being on the site of the investigation (e.g., removal of a deceased body, identification of a suspect, collection of explosive residue)
  • Determine the equipment needed to fulfill the objective.
  • Pre-package from established crime scene collection kits a ready-kit for this specific event.
  • Determine any specialized personnel that may be needed on-scene for this investigation.
  • Develop a documentation and collection plan to include:
    1. Type and nature of documentation expected
    2. Priority of evidence collection
    3. Responsibility for onsite collection
    4. Responsibility for evidence custody

Command Post and Notification Procedures

The investigator in charge should set up a temporary command post in a location where media can take necessary photographs without jeopardizing the scene (and evidence) security.  If circumstances and policy dictate transfer of the scene to another investigator, the investigator in charge should notify investigators or appropriate departments (such as Homicide) of information gathered at the crime scene.  Details of the scene are discussed in this step.

The investigator in charge should notify the Communications Department (Dispatch) of phone numbers at the command post.  The Communications Department should be asked to notify surrounding agencies and send teletypes regionally and nationally when a suspect has fled the scene. These alerts should include a description of the suspect, vehicles involved and contact information for the person these agencies should contact if they locate the suspect.  The investigator in charge should brief the supervisor as required by departmental policy. The first responder, as well as any other officers at the scene, should be debriefed.

When crime scenes are large and complex, necessary procedures will dictate that the investigator will need assistance processing and securing the scene.  The investigator in charge should make necessary duty assignments and record each on a formal assignment sheet. The assignment sheet should be updated to record assignment updates throughout the investigation. The assignment sheet should be available to all personnel working on the case.  Typical assignments include an evidence recorder and an entry/exit recorder (who is also responsible for keeping event timetable).

An early priority should be to establish the status and locations of victims and suspects. In addition,  the status of bulletins that have been broadcast regarding victims and suspects should be established. The investigator in charge will also want to ensure that missing suspect alerts are broadcast.

The investigator in charge will also want to establish a schedule for investigative team meetings (including all uniformed officers), during which status will be given, assignment updates will be made, and other key information will be shared.

Witness Management Procedural Summary

  • Interview any witnesses at the scene separately to best use their reported experiences to benefit the overall investigation.
  • Obtain written/recorded statements from each witness at the police station.
  • Transport each witness to the police station separately from other witnesses or suspects.
  • When possible, the following tasks should be performed by the Supervising Officer:
    1. Establish the status and locations of each victim and suspect.
    2. Establish the status of bulletins that have been broadcast regarding each victim and suspect.
    3. Ensure that any necessary missing suspect alert is broadcast in a timely manner.

Scene Assessment Procedural Summary

  • Converse with the first responder(s) regarding observations/activities.
  • Evaluate safety issues that may affect all personnel entering the scene(s) (e.g., blood-borne pathogens, hazards).
  • Evaluate search and seizure issues to determine the necessity of obtaining consent to search and/or obtain a search warrant.
  • Evaluate and establish a path of entry/exit to the scene to be utilized by authorized personnel.
  • Evaluate initial scene boundaries.
  • Determine the number/size of scene(s) and prioritize.
  • Establish a secure area within close proximity to the scene(s) for the purpose of consultation and equipment staging.
  • If multiple scenes exist, establish and maintain communication with personnel at those locations.
  • Establish a secure area for temporary evidence storage in accordance with rules of evidence/chain of custody.
  • Determine and request additional investigative resources as required (e.g., personnel/specialized units, legal consultation/ prosecutors, equipment).
  • Ensure continued scene integrity (e.g., document entry/exit of authorized personnel, prevent unauthorized access to the scene).
  • Ensure that witnesses to the incident are identified and separated (e.g., obtain valid ID).
  • Ensure the surrounding area is canvassed and the results are documented.
  • Ensure preliminary documentation/photography of the scene, injured persons and vehicles.

Walk-through Procedural Summary

  • Avoid contaminating the scene by using the established path of entry. Consider whether personal protective equipment (PPE) should be used.
  • Prepare preliminary documentation (e.g. notes, rough sketches) of the scene as observed. Identify and protect fragile and/or perishable evidence (e.g., consider climatic conditions, crowds/hostile environment).
  • Ensure that all evidence that may be compromised is immediately documented, photographed and collected.
  • When involved in the initial walkthrough, note the condition of the scene. Record relevant observations, which may include things such as Ceilings, doors, including entry and exit points.  Are they open, closed, locked or forced? On which side was the key? •
  • Windows: Are they open or closed? Is there broken glass? Were they locked or forced open?
  • Lights: On or off? If left on, which lights were on?
  • Shades or shutters: Open or closed?
  • Floors/Rugs
  • Interior lighting conditions
  • Odors: Cigarette smoke, gas, powder, perfume, etc.
  • Description of perpetrator (when present)
  • Description of crime-related people present
  • Description of emergency medical or search-and-rescue personnel present
  • Weapons observed
  • Furniture present, including location relative to victim, as applicable and overall scene
  • Signs of activity: Meal preparation, dishes in sink, condition of housekeeping (clean, dirty or items in disarray), appliances left on, television/stereo left on (note the channel), etc.
  • Date and time indicators: Mail, newspapers, dates on milk cartons, stopped clocks, spoiled foods, items that should have been hot or cold, but are at room temperature
  • Temperature of the room and environmental conditions
  • Develop a general theory of the crime

Team Composition Procedural Summary

  • Assess the need for additional personnel.
  • Be aware of the need for additional personnel in cases involving multiple scenes, multiple victims, numerous witnesses or unique circumstances.
  • Assess forensic needs and call forensic specialists to the scene for expertise and/or equipment.
  • Ensure that scene security and the entry/exit documentation are continued.
  • Select qualified person(s) to perform specialized tasks (e.g., photography, sketch, latent prints, evidence collection).
  • Document team members and assignments.

Contamination Control Procedural Summary

  • Limit scene access to people directly involved in scene processing.
  • Follow established entry/exit routes at the scene.
  • Identify first responders and consider collection of elimination samples.
  • Designate a secure area for trash and equipment.
  • Use personal protective equipment (PPE) to prevent contamination of personnel and minimize scene contamination.
  • Clean/sanitize or dispose of tools/equipment and personal protective equipment between each item of evidence collection and/or scenes.
  • Utilize single-use equipment when performing direct collection of biological samples.
Modification History

File Created:  05/02/2019

Last Modified:  05/15/2019

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This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

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