03 June 2, 2016
Documenting and investigating a crime scene are important procedures to investigating a crime, and assigning culpability as an investigator documents, recognizes, and collects physical evidence as the scene of a crime. In order for a crime to be solved, and culpability assigned it is critical for the investigator to reconstruct the scene by putting each piece of evidence together in order to paint a picture of what happened at the scene of the crime.
The principle that guides the crime investigation process is called Locard's Exchange Principle. This principle suggests that something physical is always added or removed from a scene whenever someone enters or exits it. Generally this principle suggests that with each contact a trace is left. This is an important approach that allows investigators to accurately link suspects to victims as well as physical evidence, and to the scene in general. Associative evidence is any evidence that can link a person to the scene of a crime, such as fibers, hair, blood and bodily fluids and fingerprints to name a few. Evidence that will help the investigator answer the question ‘who did this?’ Reconstructive evidence in contrast to associative evidence allows investigators to understand what happened at the scene, such as shoe prints, blood spatter, and gun-shot residue. Evidence that helps the investigator answer the question ‘how did it happen?’
Traces are always left at the scene of an incident whether that is a crime, accident or armed conflict. It is then necessary to document a crime scene as it is the crux of the investigation process, and as mentioned before the investigator needs to know what happened, reconstruct the events, and lastly interpret the facts as revealed to him. Traces are extremely transient and fragile so it is important for the investigator to preserve both the integrity, and reliability of the physical evidence. It is very important for the preliminary actions taken at the crime scene to be ones of caution so that the value of the evidence remains intact. Professionalism is paramount as the scene is documented so that the physical evidence maintains its integrity making it admissible in court and available for either humanitarian action or human rights inquires. Physical evidence is recovered from the crime scene, which sets a host of things into action through individual steps and critical actions. Through a systematic examination, physical evidence is retrieved, and documented carefully and methodically at the scene by the investigator in order to collect fragile evidence in such a way that it is not destroyed in order to determine what happened and who might be involved. Securing, and defining areas that are involved in the crime, and might contain evidence relevant to the crime must be done. The scene needs to be documented so that the evidence that is collected is persevered, put on a package and submitted to the forensic laboratory for analysis. As mentioned before these steps and principles are integral to the investigation of crimes.
Physical evidence is critical to the chain-of custody concept in crime scene investigations. Physical evidence can be anything ranging from a large object to very small items discover at the scene of the crime. This type of evidence place an important role in investigating a crime. Other sources of information are often affected by limited liability except for physical evidence. If the chain-of-custody is not maintained properly then the value of the evidence recovered at the scene could be in jeopardy. Chain-of-command refers to the chronological documentation of evidence. It is imperative from the beginning of a forensic process to be careful, and be able to demonstrate how each step is undertaken in the investigation process in order to ensure continuity, and traceability of evidence from the scene to the courtroom. Typically a forensic process begins from the crime scene where the evidence if identified and recovered. Then evaluation and analysis of findings are done in the forensic laboratory, and then the findings are presentenced to lawyers, prosecutors, judges and any other agent who might be in need of this factual information.
How do technicians document crime scenes?
Crime scene investigators or technicians are aware of the fact that one a criminal leaves the scene of a crime, often he leaves traces back at the scene of the crime, and the only thing he takes away would be minute material either from the victim or the scene or both. When an investigator arrives on the scene of a crime that scene serves as a guide to how the technician will process, a d document the scene of the crime. For example, the way a technician processes a burglary will be remarkably different than if he were processing the scene of a homicide. Typically a technician follows certain steps in order to document the scene of a crime, such as; 1. Establish the scene and identify possible safety and health hazards, 2. Establish security at the scene, 3. Plan, coordinate, and communicate, 4. Conduct an initial survey or walkthrough of the scene, 5.document and process of the scene, 6. Conduct secondary surveys, and interviews, and 7. Record and preserve evidence carefully.
Steps
a. Establish the scene and identify possible safety and health hazards: In this step the investigator/technician locate the main point of the scene. Often this is the main area where the action took place. It could be a ransacked room and from that point the technician is able to secure the area that appears to contain physical evidence relevant to the case. This is important to preserve the value of the evidence before others such as the media come on the scene later on. Safety is of utmost importance at this stage, the technician must be aware of biohazards, chemical hazards, and intentional traps could have been left behind intentionally by the suspect to harm the responders. Anyone who will come on the scene after the technician’s initial approach must be notified of evidentiary issues. b. Establish security at the scene: Locard’s Exchange Principle suggests that everyone entering or leaving a scene bring or take some evidence from the scene. It is necessary for the technician to quickly secure the crime scene. This can be done either with cones or yellow tapes, which innately define boundaries for people entering and exiting the scene, and whose movements will also be documented. c. Plan, coordinate, and communicate: Before physical evidence is collected the technician needs to have a plan. Typically the plan is developed from the theory the technician has about what happened based on what he sees on the scene. This will also be dependent upon the type of crime the technician believes occurred, which might cause him to interview third party witnesses. d. Conduct an initial survey or walkthrough of the scene; This is done to prioritize the collection of physical evidence. Valuable pieces of material will be identified through this initial walk-through, and this is when notes are taken, and photographs are taken of the evidence and of the scene. Important information is also documented such as whether lights were on, smells, temperature at the scene, and location of the body and so on. An evidence-free pathway could be created by these technicians in order to conduct a complete sweep of any evidence that might be in the area. e. Document and process of the scene: With a plan developed the team of will be able to conduct a thorough investigation through coordination of efforts, and collection of all relevant physical evidence. Detailed documentation occurs at this stage. This is where sketches, diagrams are taken and 3-D scanners and digital and video cameras are used to collect evidence. Technician must follow correct procedures to collect, package, and preserve the evidence, especially biological evidence. This type of evidence can easily be destroyed or damaged as a result of the weather, and other people on the scene might contaminate the evidence, and if there is poor lighting, alternate sources of light are sough in order to document evidence accurately at the scene. This typically becomes relevant for photography. f. Conduct secondary surveys, and interviews; This step is followed to ensure quality control of the scene and evidence, and g. Record and preserve evidence carefully: Descriptions of anything at the scene that is logged must have photographs to complement, and the information must be accurate or if a gun was used, tens serial number in the picture must match what is entered in the log book. This establishes the chain of custody that will follow the evidence for the life of the case.
Once these steps are followed, probative evidence is sent to the forensic laboratory for presumptive testing to determine what substance us present at the scene, for example, drug or toxin or if the stain has bodily fluids, or if the red spot in the kitchen is actually blood of ketchup. These presumptive tests allow the technician to narrow the substance from a field of possibilities, but not specific enough to determine details of compounds. These tests also helps to reduce the amount of evidence that is submitted to the lab, which expedites the process in the laboratory. With the advancement of technology, devices are now more affordable and portable, making it easier to now conduct additional testing at the scene of the crime.
These technicians are the experts on the scene and should not allow superiors or their attitudes, influence the way they process a scene. The process should not be rushed, because a technician is personally responsible for any errors he commits. Crime scene investigation is part of the forensic discipline, where there is also the focus on “who” of a crime, bloodstain pattern
analysis is a very important to address “what’ happened at a crime scene while he documents the evidence and process the crime scene.
Works Cited
Crime Scene Investigation: A Guide for Law Enforcement , 2013. Web. 02 June 2016
Crime-Scene Investigation and Evidence Collection, n.d. Web. 02 June 2016
Crime scene and physical evidence awareness for non-forensic personnel. United Nations Office on Drugs and Crime, 2009. Web. 02 June 2016
Fisher , B.A.J. Techniques of Crime Scene Investigation, 7TH Edition, 2004. Web. 02 June 2016
Lee, H.C. & Harris ,H.A. Physical Evidence in Forensic Science, Third Edition 3rd Edition,
2011. Lawyers & Judges Pub Company.
Travis, J. & Rau, R.M. Crime Scene Investigation: A Guide for Law Enforcement , 2000. Web 02 June 2016
