Crime Scene Investigation

Crime scene is a location where a crime took place or another location where evidence of the crime may be found, either indoor or outdoor. Crime scene comprises the area from which most of the physical evidence is retrieved by law enforcement personnel or crime scene investigators

A crime scene is not necessarily where the crime was committed. Indeed, there are primary, secondary and often tertiary crime scenes. For instance, the police may use a warrant to search a suspect’s home. Even though the suspect did not commit the crime at that location, evidence of the crime may be found there. In another instance, an offender might kidnap at one location (primary crime scene), transport the victim (the car being a secondary crime scene), commit another crime at a distant location (murder, for instance) and then dispose of the body at a fourth scene.

All locations where in there is the potential for the recovery of evidence must be handled in the same manner. They must be protected from interference of any kind so as to preserve any trace evidence. It is usually achieved by taping a wide area around the crime was committed to prevent access by any person other than the investigators. The first police officer at scene will cordon the scene to create a perimeter and only authorized personnel are allowed to enter.

Fig 1 : A sample of scene of crime with cordon (Source : http://en.wikipedia.org/wiki/File:US_Army_CID_agents_at_crime_scene.jpg)

The usual team involved at a crime scene including team leader, first officer arrived at scene, evidence collector, sketcher, and photographer. Their roles include the scene investigation and sketch, tagging, collection and photography of evidence. The conditions at the crime scene must be carefully recorded in great detail, as well as conserved. Only when recording has taken place can items be removed for laboratory analysis.

There is a sequence in conducting a crime scene investigation, which are: (1) Securing the scene, (2) Examine the scene (Scene walk-through and documentation), (3) Evidence tagging and collection, (4) Scene sketch, (5) Evidence storage and testing and (6) Final walk-through and release of crime scene.

1. Securing the Scene

   Upon their arrival the investigators’ top priority is to ascertain the extent of the crime scene and secure the perimeter to prevent contamination or removal of evidence. Law enforcement personnel can block off the area with tape or barricades and only allow essential staff to enter the premises.

   Once the scene has been secured an interview of victims, witnesses and suspects will provide an overview of what to expect once inside the crime scene. The first responding officer will provide a lot of information on what was found upon arrival, what has been touched, moved or removed.
2. Examine the Scene (Scene Walk-Through and Documentation)

   The next step is to “walk through” the scene to get an idea of the nature of the crime, how it was committed, point of entry and point of exit. The purpose of the walk through is to determine what needs to be more closely examined and what evidence may be present.

   Once the safest route for traveling through the scene has been determined, it is time to photograph the scene. Photographs begin with the general to the specific. A picture of the parking area may be the starting point, with shots of exterior walk ways leading to the scene following. All entry point to the scene need be photographed concentrating on the suspected point of entry. The exterior shots should present a travelogue of how access to this scene was had. Once the exterior shots have been completed the interior shots begin.

   At the same time, investigators do an initial walk-through to more closely examine and document the state of the crime scene as it was found. They especially take careful note of any important conditions that could change over time such as the room’s temperature, or fluids in the area that have not yet dried.
3. Evidence Tagging and Collection

   After the entire scene has been documented, investigators begin the search for specific pieces of evidence. This can include trace evidence (such as fibers or hair), footprint or tire impressions, fingerprints, blood or other bodily fluids and weapons. Each evidence will be tagged and collected using tweezers, gloves or tongs to prevent contamination. In some cases, entire portions of a wall, floor or large furniture may be removed for further analysis by forensic scientists.

   All photos should be taken 90o to the surface of the object being photographed. All evidence should be photographed in place as found first and later with evidentiary markers and if necessary something to assist in determining the size of the object such as a ruler, pen, coin etc. A photographic log is kept identifying each picture and the sequence in which it was taken. If fingerprint is found, a one-to-one photo will be taken.
4. Scene Sketch

   Every evidentiary item must be geographically located (measured) and sketched in a field drawing. The sketcher will do a rough sketch with true North indicator and measurement of evidence in relation to a point. Sketch is meant to be a complement to photographs taken at the crime scene.

5. Evidence Storage and Testing

   Investigators document, seal and label all evidence for transportation to a forensic lab for analysis. Depending on the type of evidence presence, some evidence may be tested on the premises as screening test and further confirmation are sent to specialists for further examination. Forensic labs can conduct a variety of types of testing: chemical analysis, microscopic examination, fingerprint analysis, DNA testing and matching, toxicology tests and more.

6. Final walk-through and release of crime scene

    

   The team leader who is the investigation officer will do a final walk-through to make sure no evidence has been missed out. When everything is satisfactory, the investigation officer will declare and release the crime scene officially.

   
   Fig 2 : Types of outdoor crime scene. (a) River (b) Forest (c) Outside of house. (Source : Department of Forensic Medicine, Hospital Kuala Lumpur)

   Crime reconstruction is part of crime scene investigation. Crime reconstruction or crime scene reconstruction is the forensic science discipline in which one gains explicit knowledge of the series of events that surround the commission of a crime using deductive and inductive reasoning, physical evidence, scientific methods, and their inter-relationships.
   Crime scene reconstruction has been described as putting together a jigsaw puzzle but doing so without access to the box top; the analyst does not know what the picture is supposed to look like. Furthermore, not all of the pieces are likely to be present, so there will be holes in the picture. However, if enough pieces of a puzzle are assembled in the correct order, the picture may become clear enough that the viewer is able to recognize the image and answer critical questions about it.

   In forensic science, there are three areas of importance in finding the answers and determining the components of a crime scene: (1) specific incident reconstruction, (2) event reconstruction, and (3) physical evidence reconstruction. Specific incident reconstruction deals with road traffic accidents, bombings, homicides, and accidents of any severity. Event reconstruction looks at connections between evidence, sequence of events, and identity of those involved. Physical evidence reconstruction focuses on such items as firearms, blood traces, glass fragments, and any other objects that can be stripped for DNA analysis.

References

1. Lectures of Faculty of Health Science, University Sains Malaysia, Health Campus, Kota Bahru, Kelantan
2. Lectures of Forensic Laboratory, Maktab PDRM, Cheras, Kuala Lumpur.