Forensics For Dummies. Douglas P. LyleЧитать онлайн книгу.
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.
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, or located by its distance from two fixed points, such as a wall, a lamppost, or a sidewalk. Doing so provides exact graphic coordinates of each item. Sketches made at the scene may be rough, but they need to be accurate. They can be redrawn later for clarity and aesthetics. Several computer programs are available that help generate clear drawings.
Illustration by Nan Owen.
Figure 3-1: Crime-scene sketches must be clear and show the coordinate positions of each item of evidence.
Reconstructing the crime scene
After doing an initial walk-through of the crime scene, the investigator begins mentally formulating a hypothesis of the crime, focusing on the likely sequence of events and the locations and positions of everyone present during the crime. Information like the following may be critical in determining the truthfulness of a suspect or the reliability of a witness:
✔ Shoeprints may reveal a perpetrator’s every step.
✔ Fingerprints may indicate the things the perpetrator touched.
✔ Tool marks may signify points of entry or where safes or locked cabinets were pried open.
✔ Blood spatters, bullet trajectories, the angle and severity of blows and stabs, and the nature of the victim’s injuries can reveal the actual and relative positions of the assailant, victim, and anyone else who was present during a crime.
✔ The physical changes that take place in a corpse (see Chapter 11) may indicate whether the body was moved several hours after death.
The investigator continually tests the developing crime theory against the evidence and avoids making any assumptions, no matter how logical they may seem. An investigator may logically believe that a piece of evidence ended up where it did because of a suspect’s actions, but if the hard evidence doesn’t support this belief, the theory must be held suspect.
If a gun is found just outside the rear door of a house where a homicide took place, logic suggests that the assailant dropped the gun while escaping. Although that’s certainly a possibility, without solid evidence, ruling out other possibilities may be difficult. For all investigators know, the gun had been tossed there in an attempt to make a domestic homicide look like a murder committed by a burglar whom the victim supposedly caught in the act. Evidence like the spouse’s fingerprints on the gun or the victim’s blood on the spouse’s shoes may, of course, change the theory, but until all evidence in a reconstruction is considered and explained, investigators can’t reach any absolute conclusions.
Recognizing a staged crime scene
Staging is when someone who’s committed a crime attempts to make the scene look like something that it isn’t. The most common staging scenario occurs when someone tries to make a murder look like a suicide or an accident. The suspect may move the body or clean certain areas. Say, for example, a husband strikes his wife in the head with a blunt object, killing her. Then he cleans up the bedroom, moves her body into the bathroom, places her in the tub, and calls the paramedics, claiming that she fell while bathing.
Other common examples of staged crime scenes include the following:
✔ A murderer breaks a window or pries a lock and makes sure a prized piece of insured jewelry is missing in an effort to stage the crime so that it looks a burglar killed the victim.
✔ One spouse secretly feeds a deadly quantity of alcohol and sedatives to the other and then forges a suicide note in an attempt to make homicide look like suicide.
✔ A person committing insurance fraud stages a breaking and entering: Jewelry is missing, a window has been pried open, and of course, the jewelry was insured.
✔ A perpetrator sets a fire (thus committing arson) to cover up another crime, perhaps a murder, embezzlement, or even a burglary. The perpetrator hopes that the fire, which becomes a staged crime scene, destroys evidence of the underlying crime.
All evidence is not created equal. In fact, evidence is divided into numerous categories depending on its characteristics and reliability. For example, an eyewitness account falls into a different classification than left-behind hair or a piece of clothing.
Determining whether evidence is direct or circumstantial