Forensic Science chapter 2 The Crime Scene

The Crime Scene

Arrival at the Crime Scene

• Upon arrival at a Crime scene, the first responding police officer to a crime scene is responsible for:

  -Acquiring medical assistance for injured victims

• Medical personnel should avoid disturbing evidence and approach the victim by an indirect route.

  - Detaining any potential suspects or witnesses

• Statements are taken from victims, witnesses, and suspects.

  -Securing the crime scene to the greatest extent possible

• The boundary is sealed off and guards are posted at the entry to the crime scene if needed.

• All civilians and unauthorized personnel are excluded from the crime scene.

  -Calling for any additional personnel needed, such as other officers and/ or forensic investigators

• The personnel required depends upon the nature of the crime scene.

Securing the scene

• The lead investigator will determine the boundaries of the scene and establish the perpetrator’s possible path of entry and exit.

• The boundaries of the crime scene must be secured with crime scene tape, ropes, or cones.

• The secured area should include the area where the crime took place and the surrounding area where physical evidence may be located.

• Once the boundaries are secured, guards may be posted to restrict access to the crime scene.

• A detailed log is kept of personnel movements in and out of the crime scene. This log includes

  personnel names and time of entry or exit.

• Investigators should never do anything that might alter the crime scene including smoking, eating, drinking, or littering.

Searching the Crime Scene

• The search for physical evidence at a crime scene must be thorough and systematic.

• The search pattern selected will normally depend on the size and locale of the scene and the number of collectors participating in the search.

• For a factual, unbiased reconstruction of the crime, the investigator, relying upon his or her training and experience, must not overlook any pertinent evidence.

• Physical evidence can be anything from massive objects to microscopic traces.

Recording Methods

• Photography, sketches, and notes are the three methods for crime-scene recording.

• Ideally all three should be employed; however, as is often the case, personnel and monetary limitations may prohibit the utilization of photography at every crime site.

Crime Scene Notes

• Note taking begins when the investigator is contacted and requested to report to the crime

  scene.

• The crime scene notes should begin with:

  -The identity of person who contacted the investigator

  - Time of contact and arrival at the crime scene

  -Preliminary case information

  -Personnel present on arrival and those being contacted

• Notes contain a personnel log, all observations made by the investigator, and the time observations were made.

• Notes are taken in a uniform layout, concurrently as the observations are made.

• Notes are written in a bound notebook in blue or black ink.

Digital Photography

• A digital photograph is made when a light-sensitive microchip captures light on each of millions of tiny picture elements, called pixels.

  -The light is recorded on each pixel as a specific electric charge which is read by the camera as image information which is stored as a file on a memory card.

• The number of pixels is directly related to the resolution of the picture. Photographs with more

  pixels show increasingly good resolution, or more detail and sharpness in photographs.

• The number of pixels that a camera features is usually measured in millions of pixels, or megapixels.

Digital Crime Scene Photography

• Advantages of digital crime scene photography include:

  -The ability to observe images immediately after taking them, ensuring important photographs are clear and show the best possible detail

  -The ability to preserve the details of the crime scene exactly as they were found

Crime Scene Photography part 1

• Crime scene photographs should record the area in which the crime actually took place and all adjacent areas where important acts occurred.

• The most important prerequisite for photographing a crime scene is for it to be in unaltered condition.

• Each crime scene should be photographed as completely as possible in a logical succession. The sequence will show the overall scene first, then work down to individual pieces of evidence that jurors in the trial will be able to easily relate back to the larger scene.

Crime Scene Photography part 2

• The four minimum photographs required at a crime scene are:

  -Overview photograph

  -Medium-range photograph

  -Close-up photograph

  -Close-up photograph with a measurement scale, such as a ruler

Crime Scene Photography part 3

• Overview photographs of the entire scene and surrounding area, including points of exit and

  entry, are taken first.

  -Taken from the outside borders of the scene and from various angles

  -If the crime scene includes a body, photographs must show the body’s position and location relative to the entire scene.

  -Include a “visual tag,” an object recorded in multiple overview photographs, to help visually

  piece the scene together.

Crime Scene Photography part 3.5

• Medium-range photographs show the layout of smaller significant areas of the crime scene.

  -Taken with evidence markers in place to show the spatial relationships between and among

  pieces of evidence in greater detail than the overview photographs

  -Include at least one photograph of the “center” of the scene.

  -In violent crimes, this usually includes the site where the victim was found and the

  surrounding area.

Crime Scene Photography Part 4

• Close-up photographs are taken last and show greater detail of individual objects or evidence.

  -Taken at a 90° angle to the object, with and without evidence markers and scales

  -Scales should be placed as close to the evidence as possible without affecting it in any

  way.

Crime Scene Photography Part 5

-After the 90° photographs have been taken, photographs from other angles may be taken.

-The most important close-up photographs are those depicting injuries and weapons lying near a body.

-After the body is removed from the scene, the surface beneath the body should be

photographed.

Videotaping Crime Scenes Part 1

• As with still crime scene photography, the crime scene video must include overview, medium-

  range, and close-up images.

• A narrated crime scene video combines photography and notes.

  -It is important that only one person narrates

  and no side conversations are captured on the video.

Videotaping Crime Scenes Part 2

• Some video cameras can produce still photographs, but the quality is often poor.

  -Therefore, still photographs from a digital camera are still required.

Body-Worn Cameras

• Cases with conflicting eyewitness accounts prompted calls for police to be outfitted with body-worn cameras (BWCs).

• These cameras have at least one microphone and internal data storage.

• BWCs are an efficient tool for collecting evidence and recording crime scenes.

Sketching the Crime Scene Part 1

• Third method of crime scene documentation:

  sketches

• Crime-scene sketches:

  -Clearly show the layout of a crime scene

  -Illustrate the relationship in space of all significant items and features

  -Clarify objects and features already described in notes or shown in photographs

Sketching the Crime Scene Part 2

• Crime-scene sketches

  -Show measurements over long distances and topography of outdoor scenes

  -Depict possible paths of entry, exit, and movement through the scene

The Rough Crime-Scene Sketch Part 1

• A rough sketch is created at the crime scene, contains an accurate depiction of the dimensions

  of the scene, and shows the location of all pertinent objects and features.

• This sketch is not drawn to scale, but it should show the accurate measurements of the distances of significant objects or scene boundaries.

The Rough Crime-Scene Sketch Part 2

• All rough sketches include:

  -Title block with information on the case, crime scene, and person creating the sketch

  -Legend with identity and dimensions of objects in the sketch

  -Compass showing the North direction

  -Body containing the sketch itself

The Finished Crime-Scene Sketch

• The finished sketch is created from the information in the rough sketch, but it is drawn to scale with care and concern for appearance.

• The current standard method utilizes computer-aided drafting (CAD) programs to create the

  finished sketch.

• CAD programs also allow for the creation of three-dimensional finished sketches.

Searching the Crime Scene Part 1

• The walkthrough is the initial survey of the crime scene.

  -Perpetrator’s point of entry and exit are located.

  -Indirect path is taken to the center of the crime scene.

Searching the Crime Scene Part 2

• Obvious items of evidence are located and documented.

  -The conditions of the scene are observed and

  recorded.

• Special attention is paid to item or conditions that suggest timing of the incident or do not appear to belong.

Searching the Crime Scene Part 3

• There are multiple different search patterns that can be employed following the initial walkthrough. The search pattern will be chosen based on the specific details of the scene at hand.

• Line/Strip Search Pattern

  -One or two investigators start at the boundary of the crime scene and search in straight lines

  across to the other side of the crime scene.

Searching the Crime Scene Part 4

• Grid Search Pattern

  -Two or more investigators form a grid by searching in line patterns that overlap and are perpendicular to each other.

• Spiral Search Pattern

  -One investigator searches in a spiral path from the center of the crime scene to the boundary

  (outward) or from the boundary of the crime scene to the center (inward).

Searching the Crime Scene Part 5

• Wheel/Ray Search Pattern

  -Several investigators search in straight lines from the center to the boundary (outward) or from the boundary to the center (inward).

• Quadrant/Zone Search Pattern

  -The crime scene is divided into smaller sections (zones). One or more investigators are

  assigned to search each zone.

Searching the Crime Scene Part 6

• Vehicle searches must be carefully planned and

  systematically carried out.

  -Investigators search interior and exterior of vehicle.

  -The vehicle may be searched at the crime scene or at the police department or crime

  laboratory garage.

Procedures for Collection Part 1

• Often, many items of evidence are clearly visible but others may be detected only through

  examination at the crime laboratory.

• For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernail scrapings, in addition to more discernible items.

Procedures for Collection Part 2

• Investigators handle and process physical evidence in a way that prevents changes to the evidence through contamination, breakage, evaporation, accidental scratching or bending, or through improper or careless packaging.

Procedures for Collection Part 3

• The use of latex gloves, disposable forceps, and sanitized equipment reduces the chance for contamination.

• Whenever possible, one should keep evidence in its original condition as found at the crime scene.

Packaging Part 1

• Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

• The well-prepared evidence collector will arrive at a crime scene with a large assortment of packaging materials and tools ready to encounter any type of situation. 

• You can use a Manila evidence envelope, Metal pillboxes, and a sealable plastic evidence bag

Packaging Part 2

• Disposable forceps and similar tools may have to be used to pick up small items.

• Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence.

Packaging Part 3

• Alternatively, manila envelopes, screw-cap glass vials, or cardboard pillboxes are adequate containers for most trace evidence encountered at crime sites.

• Ordinary mailing envelopes should not be used as evidence containers because powders and fine particles will leak out of their corners.

Packaging Part 4

• Sealable plastic evidence bags are ideal for drug evidence

• Small amounts of trace evidence can also be conveniently packaged in a carefully folded paper,

  using what is known as a “druggist fold.”

• Evidence from arson scenes should be packaged in airtight metal or glass containers to prevent the loss of accelerant vapors.

Packaging Part 5

• If biological or bloodstained materials are stored in airtight containers, the accumulation of moisture may encourage the growth of bacteria and mold, which can destroy the evidential value.

• For packaging biological evidence, the material should be allowed to air-dry before being packaged in butcher paper, manila envelopes, or paper bags.

Packaging Part 6

• Contamination is a key concern during the collection of DNA-containing specimens such as blood, saliva, sweat, or skin cells.

• Contamination can occur either by introducing foreign DNA through coughing or sneezing onto evidence, talking over items of evidence, touching one item then touching another with the same pair of gloves, or if items of evidence are incorrectly placed in contact with each other during packaging.

Packaging Part 7

• To prevent contamination, the evidence collector must wear a face mask and lab coat, use disposable latex gloves and work with disposable forceps when collecting evidence that may contain DNA.

• Disposable coveralls, shoe covers, and eye protection offer added precautions to avoid contaminating DNA evidence.

Chain of Custody Part 1

• The chain of custody is a list of all persons who came into possession of an item of evidence, as well as when and where they were in possession of it.

• Continuity of possession, or the chain of custody, must be established whenever evidence is

  presented in court as an exhibit.

Chain of Custody Part 2

• Adherence to standard procedures in recording the location of evidence, marking it for

  identification, and properly completing evidence submission forms for laboratory analysis is critical to chain of custody.

• This means that every person who handled or examined the evidence and where it is at all times must be accounted for.

Obtaining Reference Samples

• Standard/Reference sample

-Physical evidence whose origin is known, such as blood, buccal swab, or hair from a suspect, that can be compared to crime-scene evidence

• The examination of evidence, whether it is soil, blood, glass, hair, fibers, and so on, often requires comparison with a known standard/reference sample.

Submitting evidence Part 1

• Evidence is usually submitted to the laboratory either by personal delivery or by mail shipment.

• Care must be taken in packaging evidence that will be sent by mail in order to prevent breakage

  or other accidental destruction during transit to the laboratory.

Submitting Evidence Part 2

Most laboratories require that an evidence submission form accompany all evidence submitted. Case information provided on this form enables the laboratory analyst to make an intelligent and complete examination of the evidence.

Crime Scene Safety Part 1

Crime scenes frequently present the investigator with biological specimens of unknown origin; the investigator has no way of gauging what health hazards they may contain. Use caution and protection at all times.

Crime Scene Safety Part 2

• Personnel should always wear latex gloves and possibly chemical resistant clothing, Tyvek-type

  shoe covers, a particle mask/respirator, goggles, or face shields when potentially infectious

  material is present.

• Gloves should be changed often

Personnel should maintain a red biohazard plastic bag for the disposal of contaminated gloves, clothing, masks, pencils, wrapping paper, and so on.

Crime Scene Safety Part 3

• When processing and collecting evidence at a crime scene, personnel should be alert to sharp objects, knives, hypodermic syringes, razor blades, and similar items.

• Eating, drinking, smoking, eating, and chewing gum are prohibited at the immediate crime scene.

Search and Seizure Protocols Part 1

The removal of any evidence from a person or from the scene of a crime must be done in conformity with Fourth Amendment privileges:

-“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizure, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Search and Seizure Protocols Part 2

• The United States Supreme Court has determined that search and seizure without a court-approved warrant is justified in four cases:

-The existence of emergency circumstances

-The need to prevent the immediate loss or destruction of evidence

-A search of a person and property within the immediate control of the person provided it is made incident to a lawful arrest

-A search made by consent of the parties involved

Search and Seizure Landmark Cases Part 1

• In the case of Mincey v. Arizona, the Court dealt with the legality of a four-day search at a homicide scene and determined that the evidence was illegally seized because a warrant was never issued and the circumstances of the case did not justify a warrantless search.

Search and Seizure Landmark Cases Part 2

In Michigan v. Tyler, fire destroyed a business establishment leased by Loren Tyler and a business partner. The court decided that evidence obtained from the initial search was legally seized, but evidence obtained from searches 4, 7, and 24 days after the incident were illegally seized.