Fundamentals of Criminal Investigations
Adam J. McKee, Ph.D.
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Section 2.5: Conducting Searches
The first step in the collection of evidence is to prioritize such that valuable evidence is not lost, contaminated, or destroyed. This evaluation process consists of conducting a careful and methodical evaluation of all potential evidence items at the scene.
Generally, searches should be conducted such that areas that are easily accessible and in open view are searched first. After these areas are searched, then move on to out-of-view locations. Most criminal investigators will choose a systematic search pattern based on the size and location of the scene.
There are four types of search methodology that can be considered to search a crime scene:
- Lane or strip search
- Grid search
- Zone Search
- Spiral search
The size of the lane of the search should be approximately the arms’ length of the searcher. As the search of an area is completed, some marking should be made to indicate that the area has been completed. A mechanism should exist for the circumstance when potential evidence is found (e.g. who is called over, what path they should take, whether the other searches should halt moving until this finding is resolved).
Lane or Strip Searches are accomplished by the searchers walking in parallel along defined lanes in the same direction.
A Grid Search is a lane search that is conducted by completing a lane search in one direction and then completing a lane search in a perpendicular direction. While it takes twice as long as a lane search, it provides a more thorough search of an area.
A Zone Search involves dividing the area to be searched into adjacent zones. The smaller the size of the zone, the more methodical the search can be. Zone searches may be done by multiple searchers per zone.
A Spiral search involves a spiral into (inward) or out from (outward) a crime scene. A practical disadvantage with outward spiral searches is the evidence may be destroyed as the searchers move to the center of the crime scene area to begin their outward search.
It is important to choose a progression of collection and processing methods so that initial techniques do not compromise subsequent techniques. As a rule, focus on transient evidence first and move to the least transient forms of physical evidence. Likewise, move from the least intrusive processing methods to the most intrusive. It is also important to continually reassess environmental factors (e.g., sunlight, wind, rain, approaching darkness) that will affect evidence and the investigator’s ability to process the scene. It is also important to maintain security throughout processing.
Perhaps the most important aspect of evidence collection is documentation. For each and every piece of evidence, you must record its location at the scene, the date and time collected, and who collected it.
Remember that chain of custody concerns begin the moment that the evidence is identified as such.
It is also important to collect reference samples, control samples, and elimination samples from the scene.
Immediately secure electronically recorded evidence from the vicinity of the crime scene. Computers, answering machine tapes, and security camera video can easily be erased and altered.
Evidence should be stored in appropriate containers and labeled at the crime scene. It is critical that evidence containers be properly labeled. When packaging items, it is critical to consider the nature of the evidence as it relates to proper packaging. Improperly packaged evidence can be lost, destroyed, and contaminated.
When evidence must be altered before submission to the crime lab (such as making a firearm safe for transport), it is critically important to document the original condition.
As a general rule, you should avoid excessive handling of the evidence after it is collected.
When transporting evidence and submitting it for secure storage, always keep in mind the safety of the officer, the integrity of the evidence, and maintaining chain of custody.
Crime Scene Debriefing Team
When an investigation of a crime scene is completed, it is released back to the persons who routinely control it. Once this happens, any evidence not collected during crime scene processing will most likely be lost or destroyed. To prevent this catastrophic state of affairs, it is imperative that a crime scene debriefing be conducted. The debriefing enables law enforcement personnel and other responders to share information regarding scene findings. Everyone involved gets a chance to discuss the need for a followup investigation, the need for special assistance, and the establishment of post-scene responsibilities.
The first order of business is to establish the debriefing team. This should include the investigators in charge of the scene, other investigators, evidence collection personnel, and the initial responding officer. The following things should be considered by the team:
- What evidence was collected?
- What are the preliminary scene findings?
- What forensic tests should be performed?
- What further actions should be taken?
- Who will do what next?
Final Scene Survey
Once it has been determined that the scene has been adequately processed and is ready for release, a final survey of the scene is in order. This last examination accomplishes several functions. The first goal is to make sure that all evidence has indeed been collected and that no useful evidence remains at the scene. Second, it ensures that no equipment or materials are left behind by the investigative team. Finally, it ensures that no dangerous materials or conditions remain unaddressed.
In conducting the final survey, all areas identified as part of the crime scene are visually inspected. All equipment and materials generated by the investigation are removed. Any dangerous materials or conditions are reported and addressed.
Release of the Scene
The investigator should ensure that the scene Is not released until all reasonable efforts have been made to identify and collect all evidence for further examination and that all of the physical characteristics of the scene have been properly documented.
Evidence Prioritization Procedural Summary
- Identify roles of the team members (e.g., scribe, collector, packager, etc.)
- Conduct a careful and methodical evaluation considering all physical evidence possibilities (e.g., biological fluids, latent prints, trace evidence).
- Focus first on the easily accessible areas in open view and 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/collection methods so that initial techniques do not compromise subsequent processing/ collection methods.
- Concentrate on the most transient evidence (e.g., most susceptible to environmental conditions) and work to the least transient forms of physical evidence.
- Move from least intrusive to most intrusive processing/collection methods. Continually assess environmental and other factors that may affect the evidence. Be aware of multiple scenes (e.g., victims, suspects, vehicles, locations).
- Processing one scene at a time to avoids cross contaminating these various scenes
- Recognize other methods that are available to locate, technically document, and collect evidence (e.g., alternate light source enhancement, blood pattern documentation, projectile trajectory analysis).
Evidence Collection Procedural Summary
- Maintain scene security throughout processing and until the scene is released.
- Document the collection of evidence by recording its location at the scene, date of collection, and who collected it.
- Collect each item identified as evidence.
- Establish chain of custody.
- Obtain standard/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, computers) from the vicinity.
- Identify and secure evidence in containers (e.g., label, date, initial container) at the crime scene.
- Different types of evidence require different containers (e.g., porous, nonporous, crush-proof). Package items to avoid contamination and cross-contamination.
- Document the condition of firearms/weapons prior to rendering them safe for transportation and submission.
- Avoid excessive handling of evidence after it is collected.
- Maintain evidence at the scene in a manner designed to diminish degradation or loss.
- Transport and submit evidence items for secure storage.
Modification History File Created: 05/16/2019 Last Modified: 05/02/2019
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