Crime Scene Investigation | Secure and Isolate the Crime Scene

Procedure 11. Secure and isolate the crime scene.

This is the first critical step in crime scene investigation because anyone who enters the scene could potentially alter or destroy physical evidence. This also en-sures the safety of personnel working the scene, as anyone who is not supposed to enter the scene will be stopped. The entire area around the crime scene should be walked to identify the border of the scene. This will determine where the crime scene tape should be erected. If it is determined at a later date that the crime scene extends beyond this line it must be adjusted immediately. All persons who enter and exit the scene shall be documented, including name, date, time in/out, and purpose for entering the scene. If necessary all of these individuals may need to give exemplar samples to eliminate these individuals as leaving shoe prints, fingerprints, etc.

Crime Scene Investigation | Record the Crime Scene by Taking Photographs

Procedure 22. Record the crime scene by taking photographs.

The most important thing is that the scene is photographed in its unaltered and original state, before the scene is changed in any way. This records the scene as it was left by the perpetrator. If anything has been added, removed, or changed positions at this point the photographs may not be admissible as evidence in court. This includes any evidence that has been added, removed, or moved within the scene at this point.

Crime Scene Investigation | Conduct a Systematic Search for Evidence and Assign Evidence Numbers

Procedure 33. Conduct a systematic search for evidence and assign evidence numbers.

Physical evidence is defined as “any object that can establish that a crime has been committed or can link a crime and its victim or a crime and its perpetrator” (Saferstein, 2011). The areas that are searched must include all points of entry/exit that could have been used by the perpetrator(s). The search pattern that is chosen to search the scene depends upon the location and size of the scene in addition to the number of individuals participating in the search. Possible search patterns include the grid method, the spiral method, the parallel method, and the zone method.

Saferstein, R. (2011). Criminalistics: An introduction to forensic science (10th ed.). Upper Saddle River, NJ: Prentice Hall.

Crime Scene Investigation | Record State of Evidence by Taking Photographs

Procedure 44. Record state of evidence by taking photographs.

Each piece of evidence should be photographed at three distances: far, medium, and close-up. The far photograph shows the item of evidence as it is located within the entire scene, showing its location in relation to the victim, furniture, other items of evidence, etc. The medium photograph shows its relation to objects that are nearby. The close-up photographs show the item of evidence as it was left by the perpetrator. It shows the exact angle, how the item is laying, which side is facing up, etc. All close-up photographs must be taken with a scale of measurement in clear view, as this shows the exact size of the item. If rulers are not available an object with a known length should be used, such as a dollar bill or quarter, although this should be a last resort as adding objects to a crime scene should be avoided.

Crime Scene Investigation | Record the Crime Scene and the Location of Evidence by Drawing Sketches

Procedure 55. Record the crime scene and the location of evidence by drawing sketches.

A rough sketch provides a general representation of all essential objects and information. It is generally done very quickly to give an overall sense of the scene and includes measurements of the scene dimensions and all objects, including potential evidence and furniture. A more detailed sketch must also be done that is drawn to-scale using the measurements that are recorded in the rough sketch. This sketch must accurately depict all areas of the crime scene.

Crime Scene Investigation | Record the Crime Scene by Taking Notes

Procedure 66. Record the crime scene by taking notes.

These must include a detailed written description of the overall scene and include the location of all items of evidence. It should be started immediately upon arriving at the scene, before the original scene photographs are taken, and will be completed when the individual leaves the scene after processing is completed. It must be recorded when each item of evidence was identified, by whom, how it was packaged and by whom, and the disposition of the evidence after it was collected and packaged. These notes should be detailed enough to allow an individual to recreate the scene. All smells, sights, and sounds should be recorded.

Crime Scene Investigation | Process Evidence at the Scene if Necessary

Procedure 77. Process evidence at the scene if necessary.

Sometimes it is suspected that a certain area of the scene may contain valuable evidence, even though this evidence is not readily visible to the naked eye. For example, fingerprints may be developed on a door, wall, or window while at the scene. These items are generally impossible to remove from the scene without destroying the evidence and therefore must be processed on scene. This includes dusting for fingerprints, spraying suspected cleaned areas with luminol to detect blood, or spraying suspected bloody or dirty prints with a developer to enhance the print. These items should be photographed before, during, and after processing to fully document how the evidence was altered and a complete description of what was done to the evidence should be recorded in the written notes.

Crime Scene Investigation | Collect and Package the Physical Evidence

Procedure 88. Collect and package the physical evidence.

All evidence should be packaged so that there is no change in the evidence between when it was removed from the scene and when it arrives at the laboratory for examination. It must be kept in its original position as found to ensure its integrity. If the evidence must be altered in any way (i.e. rendering a firearm to be safe) it must be photo documented and details recorded in the written notes. Each item of evidence should be collected one at a time and packaged within its own container. Paper is preferred to plastic to inhibit any bacterial or enzymatic process that can alter the evidence, as well as preventing cross-contamination between different items. Each package must contain the case number, item number, location, date & time collected, by whom, and any other information as dictated by your agency. The package must be sealed with tape and the seal must be marked with the sealer’s initials and date or collection. Collection information should also be recorded in the written notes and on the chain of custody.

Crime Scene Investigation | Create and Maintain the Chain of Custody

Procedure 99. Create and maintain the chain of custody.

The chain of custody is vital to ensuring the integrity of the evidence. This is a list that contains all of the people who have had possession of the evidence. Maintaining this document properly is the best way to guarantee that the evidence will endure and questions regarding where it was and what happened to it from the time it were collected from the scene to the time it is admitted into evidence at trial. Failure to maintain the chain of custody can lead to inquiries regarding the integrity and authenticity of the evidence and its examinations, which often times leads to its inadmissibility in court.

Crime Scene Investigation | Submit Evidence to the Laboratory

Procedure 1010. Submit evidence to the laboratory.

Evidence should be delivered to the laboratory immediately after the crime scene has been completely processed. It should be delivered in a manner that is agency-dependent. Your agency will tell you where and how to deliver evidence to the appropriate person and location. Evidence should NEVER be taken home or leave the immediate possession of the person delivering the evidence. Locking the evidence in an unapproved location (such as a car trunk in a garage) can break the chain of custody and render the evidence inadmissible in court.