Presentation on theme: "FORENSIC SCIENCE Crime Scene Investigation 2 INVESTIGATORS “The wise forensic investigator will always remember that he must bring all of his life experiences."— Presentation transcript:
FORENSIC SCIENCE Crime Scene Investigation
2 INVESTIGATORS “The wise forensic investigator will always remember that he must bring all of his life experiences and logic to find the truth. This means common sense, informed intuition, and the courage to see things as they are. Then he must speak honestly about what it adds up to.” Dr. Henry Lee Chief Emeritus for Scientific Services and the former Commissioner of Public Safety for the state of Connecticut
3 First Officer at the Scene ãAAssess the crime scene ãDDetain the witness ãAArrest the perpetrator ãPProtect the crime scene ãTTake notes
Primary and Secondary Crime Scenes *Primary – where the crime actually takes place, for example, in a bank robbery the bank is the primary scene. *The secondary scene is somehow related to the crime but is not where the actual crime took place, for example with the bank robbery, the get-away car and the thief’s hideout.
Once the Scene has Been Secured… a lead investigator will start the process of evaluating the area. First the boundaries of the scene must be determined, then establish the perp’s path of entry and exit.
Testimonial evidence includes oral or written statements given to police as well as court testimony by people who witnessed an event. Physical evidence refers to any material items that would be present at the crime scene, on the victims, or found in a suspect’s possession. Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells. Source: What will evidence collected at a scene do for the investigation? May prove that a crime has been committed Establish key elements of a crime Link a suspect with a crime scene or a victim Establish the identity of a victim or suspect Corroborate verbal witness testimony Exonerate the innocent. Give detectives leads to work with in the case Types of Evidence
Step 1: Interview The first step in investigating a crime scene is to interview the first officer at the scene or the victim to determine what allegedly happened, what crime took place, and how was the crime committed. This information may not be factual information but it will give the investigators a place to start. Step 2: Examine The second step in the investigation of a crime scene, which will help identify possible evidence, identify the point of entry and point of exit, and outline the general layout of the crime scene. Step 3: Document The third step in the protocol involves creating a pictorial record of the scene as well as a rough sketch to demonstrate the layout of the crime scene and to identify the exact position of the deceased victim or other evidence within the crime scene. Step 4: Process This is the last step in the protocol. The crime scene technician will process the crime scene for evidence, both physical and testimonial evidence. It is the crime scene technicians responsibility to identify, evaluate and collect physical evidence from the crime scene for further analysis by a crime laboratory. Crime Scene Protocol Adapted from
Take photographs *As soon as possible of the unaltered scene *Prior to moving or removing any evidence *Close-ups of each item of evidence (use a scale)
Sketches *are important because they relationships of items to other things *They must be clear and show the coordinate position of each item of evidence
A rough sketch A finished sketch
Crime Scene Search Patterns *Spiral SearchGrid Method Method Search pattern often extends out from key evidence or victim. Depends on area, Actions of suspects and victim.
More search Methods *Strip, or line search, often used underwater or for very large areas.
1 more search method *Quadrant, or zone search
Kendall/Hunt Publishing Company 14 Processing Physical Evidence In order for evidence to be admissible, it must be: Legally obtained Probative—actually prove something (relevant) Identify the item Maintain the chain of possession
15 Physical Evidence Transient Evidence-- temporary; easily changed or lost; usually observed by the first officer at the scene ãOdor--putrefaction, perfume, gasoline, urine, burning, explosives, cigarette or cigar smoke ãTemperature--of room, car hood, coffee, water in a bathtub; cadaver ãImprints and indentations--footprints; teeth marks in perishable foods; tire marks on certain surfaces ãMarkings
16 Physical Evidence (cont) Pattern or Transfer Evidence-- produced by direct contact between a person and an object or between two objects. There are several ways (at least 7) of classifying evidence. In this class, we will use: âBiological âChemical âPhysical âMiscellaneous
21 Physical Evidence (cont) Conditional Evidence-- produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances within a particular event. âLight--headlight; lighting conditions âSmoke--color, direction of travel, density, odor âFire--color and direction of the flames, speed of spread, temperature and condition of fire
22 Conditional Evidence (cont.) âLocation--of injuries or wounds; of bloodstains; of the victims vehicle;of weapons or cartridge cases; of broken glass, etc. âVehicles--doors locked or unlocked, windows opened or closed; radio off or on (station); odometer mileage âBody--position; types of wounds; rigor, livor and algor mortis âScene--condition of furniture, doors and windows; any disturbance or signs of a struggle.
23 THE BODY Rigor Mortis Temperature Stiffness Time Since of body of body Death Warm Cold Not stiff Stiff Not stiff Not dead more than 3 hrs Dead between 3 and 8 hrs Dead 8 to 36 hours Dead more than 36 hours
24 THE BODY Livor Mortis Livor mortis is the settling of the blood, causing the skin to change colors. Lividity indicates the position of the body after death. When lividity becomes fixed, then the distribution of the lividity pattern will not change even if the body’s position is altered. Lividity usually becomes fixed between 10 and 15 hours after death.
25 THE BODY Algor Mortis Algor mortis is body temperature. At a crime scene, it can be obtained in two different ways. ãRectal temperature ãLiver temperature
26 Time Frame of Death â ConditionAppearance â Periphery blood drying30 min to 2 hrs â Blue-green discoloration of skin â Right and left area of abdomen24 hours â Entire abdomen36 hours â Bloating36 to 48 hours â Skin slippage4 to7 days â Absence of smell from bonesmore than 1 year
27 Time Frame of Death Eyeball Changes â ConditionAppearance â Cornea drying (eyes open)minutes â Cornea drying (eyes closed)2 hours â Corneal cloudiness (eyes open)less than 2 hours â Corneal cloudiness (eyes closed) 12 to 24 hours â Eyeball collapsemore than 24 hrs
28 One can die of a massive hemorrhage (the mechanism of death) due to a gun shot wound through the head (cause of death) as a result of being shot (homicide), shooting yourself (suicide), dropping a gun and it discharging (accident), or not being able to tell which (undetermined). All of which are manners of death. THEREFORE,
Crime Scene Challenge *Now that your eyes and brain are warmed up, let’s test your observation skills a bit more. *You will have 2 minutes to study the photograph of a crime scene on the next slide. *Try to pay attention to details as you will be asked 10 questions about the crime scene! *You are not allowed to write anything down until after the time is up. *Ready?
Do you remember? * What color coffee mug was in the picture? Blue Red Yellow *2. When was the deadline? Yesterday Today Tomorrow *3. What time was on the clock on the wall? 10:40 11:05 1:55 *4. How many sticky notes were on the whiteboard? Four Six Eight *5. Which of the following was NOT in the picture? Stapler Trash Can Printer * 6. What was the name on the plaque on the desk? Bill Brian Carl * 7. What color was the victim's shirt? Black Blue Red * 8. How many plants were in the picture? None One Two *9. What was the color of the marker in the desk drawer? Red Blue Green *10. Where was the book in the picture? On a box In the trash can Under the body Kendall/Hunt Publishing Company 31