In simple terms, a crime scene is the immediate and surrounding area where a crime has been committed. A crime scene is any physical scene, which may provide potential evidence to an investigator. It may include a person’s body, any building, vehicle, and places in the open air or objects found at those locations.
The location of a crime scene can be the place where the crime took place or can be any area that contains evidence from the crime itself. Scenes are not only limited to a location. It can also can be any person, place, or object associated with the crime that occurred.
Jewellery, mobile phone, watch, pen, diary, handkerchief, etc. may be removed from the scene of crime or dropped as the perpetrator flees the scene. Cigarette butts, beverage containers or any evidence capable of the transfer of biological evidence are sometimes found in and around the scene of crime.
Different types of crime scenes include outdoors, indoor, and conveyance:
Outdoor crime scenes are the most difficult to investigate. The exposure to elements such as rain, wind, or heat, as well as animal activity, contaminates the crime scene and leads to the destruction of evidence. Other factors such as, not properly securing the crime scene can also lead to contamination of evidence. If a crime were committed outdoors and indoors then the outdoor crime scene is the priority. It is very difficult to process outdoor crime scenes at night. Regardless of the lighting used to enhance visibility, it is harmful to the evidence. This can cause loss and destruction of evidence. Therefore, if at all possible, it is best to preserve a crime scene for daylight processing. Destruction or deterioration of evidence due to environmental conditions, such as heat, cold, rain, snow and wind call for rapid and effective protection of biological evidence. Evidence that cannot be protected under these conditions should be quickly collected.
Indoor crime scenes have a significantly lower chance of contamination because of the lack of exposure. The contamination here usually comes from the people factor. The possibility of loss and contamination from multiple people accessing the scene is greatly increased.
Conveyance crime scenes relate to the commission of crimes like robbery, rape and homicide, etc. using any transport vehicle. Physical evidence recovered from these scenes may extend well beyond the vehicle used in that commission of crime. Suspects leaving in a hurry may carelessly leave additional evidence. The vehicle used in the commission of crime may be transported to the laboratory after proper documentation has been completed.
A crime scene consists of the location of where the crime was committed, any means of transport of a victim, any secondary locations (graves, dump sites, etc.) and the victim himself.
The purpose of crime scene investigation is to establish what happened (crime scene reconstruction) and to identify the person responsible for the commission of crime. This is done by carefully documenting the conditions at a crime scene and collecting all relevant physical evidence. The ability to recognize and properly collect physical evidence is oftentimes critical to both solving and prosecuting violent crimes. The enforcement officer who protects and searches a crime scene plays a critical role in determining whether physical evidence will be used in solving violent crimes.
The purpose of examining a crime scene is fourfold:
Crime scene investigators document the crime scene. They take photographs and physical measurements of the scene, identify and collect forensic evidence, and maintain the proper chain of custody of that evidence. Crime scene investigators collect evidence such as fingerprints, footprints, tyre tracks, blood and other body fluids, hairs, fibers and fire debris. Various steps in the process of investigation of crime scene include the following:
Crime scene preservation starts soon after the incident is discovered and reported to the police station. After a crime scene has been discovered, measures must be taken to secure and protect the scene from contamination. All scenes, indoor, outdoor or vehicles should be protected at the earliest opportunity to reduce the risk of the loss or contamination.
In order to maintain the integrity of the scene, law enforcement must take action to block off the surrounding area as well as keep track of who comes in and goes out. By taking these precautions, officers can ensure that evidence that is collected can be used in court.
Investigators should ensure that scenes (including the victims as well as the locations and the evidence at that location) are not interfered with. Interference, leading to forensic contamination, can be avoided by simple measures like:
All personnel attending the crime scene have a responsibility to ensure their actions do not compromise the recovery of forensic evidence. Scene preservation measures should include:
Locking down the crime scene means that all ongoing activities inside the crime scene must stop. Everyone must leave the crime scene to a location some distance from the crime scene area. Once everyone has been removed from the crime scene, a physical barrier, usually police tape, is placed around the outside edges of the crime scene.
The size of a crime scene is usually defined by the area where the criminal acts have taken place. This includes all the areas where the suspect has had any interaction or activity within that scene, including points of entry and points of exit.
According to Locard’s Exchange Principle, every person who enters or exits the scene will add or subtract material from the crime scene. Therefore, it is crucial to quickly secure the area. The crime scene may be cordoned off with yellow crime scene tape, cones or by other means. In addition, a common entryway is often established that all crime scene personnel will use to enter and exit the scene. All people entering or leaving the scene are documented once the boundaries have been established.
Scenes should be searched systematically and thoroughly for the relevant materials, targeting and prioritizing areas which are most likely to yield significant material of evidential value. Before collecting evidence, investigators must first develop a theory regarding the type of offence that was committed. Knowing the type of crime will help investigators anticipate the evidence that could be present. This may require gathering of information from witnesses or persons of interest. Based on this information, the crime scene team will develop an evidence-collection strategy taking into consideration weather conditions, time of day and other factors.
In order to help establish the linkage of people and things to a scene, the investigator may also collect known substances, called control samples. These can be items such as fibers from carpeting at the scene, glass fragments, soil, vegetation and other trace evidence. If these are found on the suspect’s clothing, in his vehicle or at his residence, it may provide circumstantial evidence linking the person to the scene of crime. For example, police are called to a residential neighborhood where a house has been invaded and burglary has just occurred. Investigators collect glass fragments from a shattered cabinet door with a distinct pattern etched into the glass. A tip leads investigators to a local man with a known history of burglary. Examination of the suspect’s clothing yields glass fragments with the same distinct pattern as the smashed cabinet doors. Eliminating people who could not be the perpetrator is also important. Control samples of fingerprints and DNA are often collected from any person(s) who have access to the scene who are not considered suspects.
Recovered material should be handled as little as possible and packaged at the earliest opportunity. All items should be packaged and sealed as soon as they are taken, using bags or containers of an appropriate size to avoid the packaging being damaged or the seals being broken.
The method of transport should be chosen to ensure that the integrity and state of preservation of the materials is maintained.
Precautions must be taken to ensure the integrity of evidence, reduce the risk of contamination and minimize degradation. These will include:
Sunil Sharma is an advocate; editor and compiler of legal commentaries, having authored more than 40 books.