Forensics For Dummies. Douglas P. Lyle

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СКАЧАТЬ been installed. Doing so can greatly narrow the focus of the investigation and lead police to the primary crime scene and the perpetrator.

       Arriving at a crime scene

      Regardless of whether the first officer to arrive at a crime scene found out about the crime via a phone call to the station, a radio call from a dispatcher, or directly from a concerned person, the officer must make every effort to detain the person who initially reported the crime and not allow that individual access to the crime scene. Anyone who reports a crime may have witnessed the incident or may have seen or heard something suspicious.

      However, because the officer has no way of knowing whether the person reporting the crime is a witness or a suspect, allowing the informant access to the crime scene can mean losing or contaminating the evidence. After all, a perpetrator may

      ✔ Believe that reporting the crime makes him less likely to be a suspect

      ✔ Attempt to destroy or remove evidence

      Neither of these situations is uncommon, so the officer who arrives first needs to approach the crime scene in a logical and organized manner, protecting the evidence and other people who may be there. Otherwise, harm may come to the officer, fellow officers, victims, witnesses, suspects, and even the perpetrator, or evidence may be damaged or destroyed.

      The officer who responds first must make personal safety a primary concern and ensure that the perpetrator or perpetrators no longer are present or a threat. Whenever a perpetrator is present, the officer arrests and secures that person. Thereafter, the officer assists any victims who are present, offers first aid as needed, and mobilizes emergency medical services. After these important tasks are completed, the officer begins preserving the crime scene.

      

Additionally, the officer may need to detain suspects and witnesses and keep them separate to avoid collusion, meaning that the detainees work together to create a story to tell police. However, at this stage, the officer may not know who is who: A witness may become a suspect, and a suspect may actually be a useful witness. Furthermore, the officer may have no reason or legal right to detain some witnesses and thus must obtain accurate identification and contact information from each person who leaves the area.

      

At the heart of crime-scene protection is the principle of exchange. Locard’s Exchange Principle (see Chapter 1) states that when any two people come in contact with each other, they exchange or transfer trace materials, such as hair, fibers, and prints. Every person who enters the crime scene can leave behind evidence of his presence; take away crucial trace evidence on his shoes, clothes, or hands; or otherwise damage or alter any evidence that remains. Thus, access to the scene must be restricted immediately and denied to all witnesses and suspects.

       Preserving and processing the scene

      The size of a crime scene can vary greatly and the police must be prepared to quickly determine its boundaries. This task is not as easy as it seems. A crime scene may be a single room, an entire house, everything on a property, or even a whole neighborhood. And that’s just the primary scene.

      

At a minimum, the crime scene includes

      ✔ The exact spot where the offense took place

      ✔ Areas from which the site can be entered and exited

      ✔ Locations of key pieces of evidence, such as the body in a murder, a safe or cabinet in a burglary, or an entire structure in a suspicious fire

      A crime scene can be cordoned off using crime-scene tape, barricades, automobiles, or even by police officers standing guard. Only personnel who are absolutely necessary for processing the scene are allowed in. This restriction often is more difficult to accomplish than you may think. A victim’s family members or neighbors may be emotionally unstable and thus difficult to remove from the area. And, of course, members of the press often have clever ways of gaining access to a crime scene, to say nothing of a captain or other high-ranking official trying to push her way past a lowly patrol officer who’s following orders to keep everyone without a reason for being there away from the scene. Furthermore, you can never underestimate the meanderings of the curious bystander.

      

After the scene is secured, the first officer to arrive establishes a security log, which basically is a sign-in sheet that must be signed by any and all visitors to the scene. This kind of crowd control helps the investigation in many ways, not the least of which is limiting the number of people who must be examined when stray fingerprints and shoeprints are found. If investigators can be ruled out, the print or prints remaining may point to the perpetrator.

      A crime-scene investigator begins by doing a walk-through examination, getting a feel for the scene and organizing an approach to collecting evidence. During this overview, the crime-scene investigator typically doesn’t examine any particular pieces of evidence, but rather looks at the big picture before beginning the tedious work of evidence examination and collection.

       Documenting the procedure

      While a crime scene is being processed, everything that transpires is documented in notes, sketches, and photographs, and perhaps even videoed. This documentation includes not only the scene and the evidence, but also the surrounding area, particularly the perpetrator’s possible entry and exit points.

      A designated note taker keeps an accurate account of all activities in and around the crime scene. Sometimes a tape recorder is used, and the verbal notes are transcribed later. Regardless of how they’re taken, the notes must be detailed, including an overall description of the scene; an accurate list describing what each piece of evidence is; when, where, and by whom it was found; and who transported it to the crime lab. The note taker also identifies and comments on every photo that is taken at the scene.

      Photographs of the scene need to be taken as soon as possible so that they show the scene preserved in an unaltered condition. Photos must be taken prior to moving or removing any evidence (or the body, if there is one). Taking several overview images of the area is a good idea, and if the scene happens to be outdoors, pictures of surrounding areas should be taken from multiple angles and points of view. Close-ups of each item of evidence, and, in murder cases, any and all visible injuries to the corpse (while it’s still at the crime scene), are critical. Video possesses the advantage of including sound so that comments can be preserved. But whenever video is used, still photos nevertheless need to be taken because they offer much greater detail resolution.

      Photos also are taken of any injured parties, including the suspect. Full-body and close-up shots of any injuries are obtained. Whether these pictures are taken at the scene or at the hospital (or even in the operating room) depends upon the nature of the injuries. Bumps, bruises, and scratches can be photographed at the scene, but photos of injuries such as gunshot and knife wounds probably have to wait until the victim is transported to the hospital.

      

In photographs where the size of the object or evidence being recorded is important, the photographer includes a point of reference. A ruler is ideal, but another common object, such as a cigarette pack, a ballpoint pen, or a car key, for example, works in a pinch.

Sketches also are extremely important, because they show the relationship of each item of evidence to other items or to the body (see Figure 3-1). Each piece of evidentiary material is mapped, СКАЧАТЬ