The discoveries, inventions, and theories of our forensic science fore bearers have all culminated into what we know today as the criminal investigation. Often, that investigation begins upon discovery of a crime scene. The information on criminal investigations, and crime scene procedure, is covered in scores of books. A basic overview of crime scene procedures is covered below.
First Responder Priorities:
- 1. Determine need for medical assistance
- 2. Confirm or pronounce death
- Conduct a scene walk through
- Take steps to preserve and protect area
- Secure and isolate the crime scene using ropes or barricades
- Exclude all unauthorized personnel from scene
- Determine the lead investigator
Physical evidence can be rendered useless by people wandering through the area. Every single person has the potential to destroy valuable evidence. It's the responsibility of the officer to prohibit access to anyone not directly involved with processing the site (including fellow officers).
Evaluation of the Area
- Determine the boundaries of the scene
- Establish the perpetrator’s entrance and exit
- Initial walk though of the scene to determine the strategy for documentation of the entire crime scene.
DOCUMENTING THE SCENE
- Overall Photos
- Photographs must be in unaltered condition.
- Overview photographs are taken of the entire scene and surrounding areas, including walls and points of entry and exit.
- The purpose is to include as much as possible in one photograph.
- The goal is to ensure that each important item is in at least one photo.
- Should be taken before anything is disturbed
- Photographs of physical evidence: should show the position and location relevant to the scene.
- Photographs of the body: should show the body's position relative to the scene.
2. Mid Range Photographs
- The purpose is to focus attention on a specific object.
- Scales should be used when indicated. Without a scale, many photos can't be admitted in court.
- Photos of wounds and bruises should be photographed with and without scales.
3. Close up Photographs
- The purpose is show a specific aspect of an object up close.
- Photos can show pattern of injuries
- Photos showing injuries or weapons lying near the body are necessary.
- After the body is removed, close up photos should be taken of the area underneath.
- Same principles used in regular photography apply.
- Overview shots as well as close ups should be taken.
SKETCHING THE SCENE
- Shows all recovered items of physical evidence
- Objects are located by distance measurements from two fixed points.
- Distances marked must be accurate. All distances are made with a tape measure.
- Each item is assigned a letter or number.
- The sketch shows a compass heading designating north.
- Usually prepared with the aide of templates
- Usually drawn to scale
- Must contain information contained in the rough sketch
- Required in court
- Includes a detailed written description of the scene
- Identifies the time an item was discovered, by whom, how and by whom it was packaged, and the disposition of the item.
- Notes are used to refresh memories, sometimes years later.
SEARCHING THE SCENE
Conducting the search for evidence is the responsibility of the lead investigator. A thorough search is imperative and no important evidence should be overlooked. Failure to collect all pertinent evidence may lead to charges of negligence or tampering.
Types of Searches
- Zone Search: A small area or room is searched. It's used in homicides, rape, drug and bomb searches.
- Ever Widening Circle: The searcher starts in the middle of the ring and continues in an ever widening circle until the whole area is searched. This is used when only one person is available to search.
- Straight Line Search: Used outdoors for body dump search and after mass disasters. A large number of people will stand, shoulder to shoulder, and walk across the area in a straight line.
- Strip Search: Used for when only a small number of people are available to cover a large outdoor area. With this search, the searchers will walk straight and then turn at right angles across the area to be covered. Down, across, up, across, down, across, up....
- Grid Search: This type covers a large area. The area is divided into a grid and a search is made of each grid. A second search will then be made perpendicular to the first search.
The search will start at the immediate area at and around the body and move outward. All areas, including ceilings, windows, doors, and floors must be examined for evidence. Any item which may carry trace evidence must be collected. Some examples of areas and things to be searched for are listed below:
- The victim
- Book cases
- Papers, magazines, and mail
- Kitchen - Check for place settings at table, number of place settings, food present and condition of food.
- Heating Conditions - check type; vented or unvented; thermostat setting.
- Wastebaskets and trash cans
- Clocks and watches
- Stairs, passages, entry and exit
- Check for tool marks
- Check for signs of ransacking and general disorder
- Check for signs of a fight
- Check odor of rooms
- Check for blood, hair, signs of body fluids, fingerprints, footprints, etc.
- Check for hiding places for weapons behind stoves and bookcases, under beds, up on high furniture, under the mattress, etc.
A large area will be searched, using personnel with metal detectors and sifters. The search will usually be completed using the straight line, strip or grid method. Some of the things the searchers will be looking for are: fingerprints, footprints, tire tracks or prints, bloodstains, scratches, paint flakes, hair, fibers, etc. Soil samples are also taken in order to compare traces of mud or soil on the suspect's clothing later. In some cases, collecting samples of the surrounding vegetation and insects can also prove useful.
If a vehicle is suspected in the commission of a crime, a meticulous search is done all over the vehicle, including the carriage underneath. Officers will be looking for dents, scratches, scrapes, paint, hairs, fibers, bits of glass, pieces of clothing, etc. A special vacuum cleaner is used to catch minute traces of evidence. In vehicles, soil accumulates under fenders and bodywork. When two vehicles collide, the soil or mud may be dislodged. By doing a soil comparison, it can later be determined if a particular vehicle was present at the crime scene.
COLLECTION OF EVIDENCE
The collection of physical evidence is vital to any crime scene search. The goal of collection is to maintain the integrity of the evidence. Physical evidence can be anything from huge items to minute traces of blood, dust, and fibers which can only be examined in the crime laboratory. Physical evidence must be handled in an exact manner thus preventing any contamination of the evidence. Blood evidence, for example, cannot be packaged wet or it will grow mold. The handlers need to try to prevent any change from taking place from the time the evidence is collected at the scene until it reaches the laboratory.
EXAMPLES OF PHYSICAL EVIDENCE
- Blood, semen, saliva, sweat
- Powder residues
- Plastic and rubber items
- Tool marks
- Wood and metal objects
PACKAGING OF EVIDENCE
Correct packaging techniques are vital to maintaining the integrity of the evidence. If the evidence is allowed to become contaminated, damaged or evaporated through mishandling, it becomes worthless. A primary rule of packaging evidence is that, whenever possible, the items should be sent to the crime lab intact. Rather than remove evidence from the object, it's preferable that the entire object be sent to the laboratory. If evidence must be removed, forceps or swabs can be utilized. If a swab is used, the swab must be air dried before packaging.
Folded papers, labeled envelopes and paper bags are often supplied and are useful for packaging evidence such as hair, blood and other body fluids, and debris. Ordinary manila envelopes should not be used, since tiny particles can leak out. Each distinct item must be packaged in separate paper bags to avoid cross contamination.
Wet evidence, such as blood, semen, and saliva, must be air dried first. Any wet evidence can grow mold which can cause the evidence to deteriorate. Once dried, the evidence can be sealed in an envelope, then packaged in a paper bag, sealed and marked accordingly. All items of clothing must be air dried then placed in separate paper bags. Other containers which can be used include: screw top glass vials, plastic pill bottles, cardboard boxes, and metal paint cans. Some examples are given below:
- Arson Material - metal paint can
- Blood, Semen, and Saliva (dried) - paper bags
- Blood (liquid) - glass vial
- Clothing - paper bag
- Fingernail Scrapings - envelope, then paper bag
- Bullets - cardboard box
- Fibers - envelope, then paper bag
- Drugs - plastic bag
- Paint - metal box
- Soil - paper bag
CHAIN OF CUSTODY
A continuous chain of custody must be maintained in order for evidenceto be accepted in court. Standards require that every person who handles the evidence must be accounted for. A log is created, for every piece of evidence, from the beginning of the crime scene investigation until the evidence is released to the crime laboratory. This includes the name, date, description, and location of the item, as well as the handler's name and title.
Once in the laboratory, the forensic examiner's signature, the incoming and examination dates, the times, and the department are also logged in. In order to avoid confusion or questionable handling, the evidence should be handled as minimally as possible.
DISBURSEMENT OF THE BODY
- Maintain integrity of evidence on the body
- Ensure the body is protected from further trauma or contamination.
- Wrap hands and feet in paper bags
- Establish victim's identification
- Participate in scene debriefing
- Notification of appropriate agencies
- Notification of next of kin *
- Inventory and secure property, clothing, and personal effects that are on the body. Remove in a controlled environment with a witness present.
- Blood and/or vitreous samples are recovered prior to release of remains.
- Ensure the labeling, packaging, and removal of the remains.
- Secure transportation of the remains.
Republished from original Forensics Talk weblog site