A Guide for General Crime Scene Investigation: Processing the Scene
Following the walkthrough, the investigators in charge should create an investigation team and process the scene. They should work with the investigation team to follow these steps:
- Determine team composition.
- Control contamination.
- Document the scene.
- Prioritize evidence collection.
- Collect, preserve, inventory, package, transport and submit evidence.
Determine team composition. The investigator(s) in charge should determine which personnel and resources are needed on the investigation team to perform scene processing.
The investigator(s) in charge should:
- Assess the need for additional personnel. Be aware of the need for additional personnel in cases of multiple scenes, multiple victims, numerous witnesses or other circumstances.
- Assess forensic needs. Call forensic specialists to the scene for their expertise and/or equipment.
- Maintain scene security.
- Continue documenting entries and exits from the scene.
- Select qualified people to perform specialized tasks such as photography, sketches, latent prints and evidence collection.
- Document team members and assignments.
Control contamination. The investigator(s) in charge must control contamination and cross-contamination at scenes to ensure scene safety and evidence integrity.
Team members should:
- Limit scene access to people directly involved in scene processing.
- Follow established scene entry/exit routes.
- Identify first responders and consider collecting elimination samples.
- Designate a secure area for trash and equipment.
- Use personal protective equipment (PPE) to keep officers from harm and minimize scene contamination.
- Clean/sanitize or dispose of tools/equipment and PPE between evidence collections and scenes.
- Utilize single-use equipment when collecting biological samples.
Document the scene. The investigator(s) in charge must ensure that the scene is documented, and determine the kind of documentation required (e.g., photography, video, sketches, measurements and notes).
Team members should:
- Review the assessment of the scene to determine the type of documentation needed.
- Coordinate photographs, video, sketches, measurements and notes.
- Photograph:
- The entire scene utilizing overall, medium and close-up coverage.
- Evidence that will be collected with and without a measurement scale and/or evidence identifiers.
- Victims, suspects, witnesses, crowd and vehicles.
- Additional perspectives (e.g., aerial photographs, witness' view of the scene and the area under the body once the body is removed).
- Use videotape to supplement photos.
- Prepare preliminary sketch(es) and measure:
- The immediate area of the scene noting case identifiers and indicating north on the sketch.
- The relative location of evidence (correlate evidence items with evidence records).
- The size of the evidence before collection.
- The rooms, furniture or other objects.
- The distance to adjacent buildings or other landmarks.
- Generate notes at the scene that:
- Document the location of the scene, time of arrival and time of departure.
- Describe the scene as it appears.
- Record transient evidence (e.g., smells, sounds and sights) and conditions (e.g., temperature and weather).
- Document circumstances that require departures from the usual procedures.
Prioritize evidence collection. The investigator(s) in charge and the investigation team should prioritize evidence collection to prevent loss, destruction or contamination.
Team members should:
- Conduct a careful and methodical evaluation that considers all physical evidence possibilities (e.g., biological fluids, latent prints and trace evidence).
- Focus first on the easily accessible areas in open view and then proceed to out-of-view locations.
- Select a systematic search pattern for evidence collection based on the size and location of the scene(s).
- Select a progression of processing and collection methods so that initial techniques do not compromise subsequent methods.
- Concentrate on the most transient evidence and work to the least transient forms of physical evidence.
- Move from least intrusive to most intrusive processing and collection methods.
- Regularly assess environmental and other factors that may affect the evidence.
- Remain aware of multiple scenes (e.g., victims, suspects, vehicles and locations).
- Recognize other methods that are available to locate, document, and collect evidence (e.g., alternate light sources and blood pattern documentation).
Collect, preserve, inventory, package, transport and submit evidence. Team members should carefully collect, preserve, package and transport evidence.
Team members should:
- Maintain scene security throughout processing and until the scene is released.
- Document evidence collection by recording its location at the scene, the date of collection and who collected it.
- Collect each item identified as evidence.
- Establish a chain of custody.
- Obtain standard and reference samples from the scene.
- Obtain control samples.
- Consider obtaining elimination samples.
- Immediately secure electronically recorded evidence (e.g., answering machine tapes, surveillance camera videotapes and computers) from the vicinity.
- Identify and secure evidence in containers (e.g., label, date and initial container) at the crime scene. Different types of evidence require different containers (e.g., porous, nonporous and crushproof).
- Package items to avoid contamination and cross-contamination.
- Document the condition of firearms/weapons prior to rendering them safe for transportation and submission.
- Avoid excessively handling the evidence after it has been collected.
- Maintain the evidence at the scene in a manner designed to diminish degradation or loss.
- Transport and submit evidence items for secure storage.
Next section: Completing and Recording the Crime Scene Investigation.
