Contact at the Scene
Preliminary Survey or Crime Scene Walk-Through
Scene Search for Trace Evidence
Scene Search for Biological Evidence
Crime Scene Photography
Evidence Marking and Packaging
Establishing the Chain of Custody
Upon arrival at the crime scene, the crime scene investigator will make contact with either the detective/officer who requested the crime scene processing services, or with the detective/officer assigned to oversee or manage the crime scene.
1) Information exchange.
After contact with the detective or officer in charge of the crime scene, the crime scene investigator will obtain the following information:
Additional information may be required due to the type of crime scene investigation including the following:
2) Scene processing request or specific directions.
A preliminary survey or walk-through of the crime scene with the detective or officer in charge should take place after the exchange of information. The investigator establishes a path to enter and exit the scene, avoiding the pathway used by the suspect, if possible, and preserving the scene from possible contamination. During this walk-through the crime scene investigator will do the following:
Trace evidence is any material such as hairs, fibers, glass, soil, paint, etc., found at a crime scene on a person or object. Trace evidence may be used to associate an individual(s) with a crime scene or another individual.
Crime scene investigators should be trained to recognize trace evidence, understand the potential value of trace evidence, and collect and preserve the sample and the control sample. When encountering noticeable items of trace evidence, document and collect the item immediately. Document and collect additional items, depending upon the conditions at the scene and stability of the item of evidence.
The investigators should have the following equipment available for use in the search and collection of trace evidence:
If trace evidence is found, it should be photographed and noted to include the following:
Crime scene investigators may search a crime scene, other locations associated with a crime scene or individuals for suspected biological evidence (i.e., blood, semen, spit).
When suspected biological evidence is identified, collect a sample for biological analysis or collect the entire item. When collecting the item, make a mark near the area where the sample was found (with a Sharpie or other marker). An arrow, line or circle should be made clearly indicating the location of the substance. Document the notes appropriately including:
Crime scene photography is one of the most important duties that the crime scene investigator performs. Visual communications are substantiated and verified by quality, concise and accurate photographs of both the scene and the evidence as it was found. Photography of the scene and of evidence is one of the first procedures performed at a scene. This generally occurs after the note-taking process has begun.
Vehicles recovered at a crime scene or other location should be photographed along with an associated landmark. Take photographs of the vehicle from a distance, if necessary, in order to include the landmark.
Some biological evidence which is not easily identified with the naked eye may be visualized with chemical enhancement or observed with an alternate light source.
Investigators may use chemical enhancements, such as luminol, when visualizing areas with small amounts of blood. Luminol causes a chemical reaction to occur with blood, resulting in luminescence or glow. This process must be conducted in darkened areas to see and document the chemical reaction.
Filtered photography techniques may be used at a crime scene to document evidence that is viewed with an alternate light source. A Luma-Lite or a Poliray® light is an example of an alternate light sources. Both units are transportable and may be taken to crime scenes to search for evidence. The alternate light sources are primarily used in the following manner:
Case files may be prepared for each of the following:
Case files may contain the following:
Rough sketches, diagrams and formal diagrams should be drawn on approved agency forms or graph paper.
Sketches and diagrams should document the scene fully, including the following:
Investigators should perform the evidence collection process in a systematic and careful manner. The process begins with the preliminary crime scene survey/walk-through, followed by a determination of the evidence collection sequence to be used.
The evidence collection sequence may be based on the following information:
Investigators should use the appropriate equipment when collecting evidence. Collection equipment that may come into contact with evidence should be sterile.
The following equipment may be used in the evidence collection process:
The swabbing collection technique should be used for the recovery of biological evidence in a dried or liquid state. Best practice techniques include the following:
Dried Material Collection Technique
Liquid Material Collection Technique
All evidence collected at a crime scene, or received at or during a crime scene investigation, is inventoried and packaged prior to leaving the scene to prevent loss or cross-contamination. Mark the item of evidence when possible. Evidence which cannot be marked, such as soil, hair and stains, should be placed in an appropriate container or envelope. Marking some items directly may interfere with forensic analysis of the item. Always mark the outer packaging.
When marking evidence directly, include the following:
Evidence that has been inventoried, marked and prepared for submittal (or to be returned to the investigating agency) is packaged in an appropriate container and labeled per agency protocol.
All outer packaging is marked with the following information:
Containers that have been inventoried and marked are sealed with agency-approved evidence tape prior to submittal or release to the custody of the investigating agency. Evidence tape is used to seal the packaging and is marked with the investigator's name or initials and the date sealed.
The chain of custody is a tracking document beginning with detailed scene notes that document where the evidence was received from or collected. The chain of custody is initially established when an investigator takes custody of evidence at a crime scene, or when evidence is received from an officer or detective at, or from, the crime scene.
The chain of custody is established through a process that includes the following:
Many agencies transfer evidence to a property room prior to submission to a crime laboratory. Property room documentation or secure electronic transfer is used when the investigator submits evidence to the property room.
The associated information may include the following:
The list of the evidence/property may include:
The chain of custody documents the transfer of evidence/property from an investigator to another individual, location or agency.
The following information is included in the chain of custody:
Two reporting formats may be used by an agency. The crime scene report is used to report crime scene activities and processing results. The second is used when analyzing evidence in the laboratory.
Article posted February 6, 2015