Forensics Unit 4 Part 1 Notes

• COMMON TYPES of PHYSICAL EVIDENCE TAPE Classify - color, width, type of tape, etc..... Individualize - jigsaw fit
• PAINT 
  • CLASS CHARACTERISTICS - Physical and chemical analysis of paint evidence (chips or residue) can indicate it's class, such as automobile paint, house paint, nail polish, etc. The evidence can be compared to 40,000 different types of paint classified in a database, which can be used to identify a particular make or model of car or brand of tool. 
  • INDIVIDUAL CHARACTERISTICS - Paint evidence can also indicate individual characteristics if an investigator is able to find similarities between two samples, such as the color, number of layers, chemical composition, or a physical match between the edges of two paint chips - one from a tool and one from a crime scene.
• GLASS 
  • Glass particles can be found at various crime scenes: breaking and entering, hit and run, vandalism, or murder. 
  • CLASS CHARACTERISTICS - color, surface characteristics, tint, thickness, density, chemical composition, and refractive index (RI) are analyzed to tell us the type of glass. 
  • TRACE ELEMENT ANALYSIS can match glass to the factory and batch number. 
  • INDIVIDUAL CHARACTERISTICS – jigsaw fit a piece of glass into the original. Matching glass from a crime scene to a headlight to a suspect's car. 
  • RECONSTRUCTION – Determine the order of bullets through glass, the direction of force that broke the window, who shot first, etc.
  • VEHICLE LIGHTS Questions may arise as to whether or not lamps were burning during a night time traffic accident. A driver may have failed to turn on the vehicle's lights, one or more lamps could be burned out, the vehicle's electrical system may be malfunctioning to the extent that it can not energize the lamps to burn. If the lamp is energized and burning, the filament becomes ductile due to its very high temperature. If the filament has ductile distortion where it is deformed into a significant bow shape or has been stretched or pulled to one side or the other between its supports where the filament coil is no longer straight and uniform and the bow or stretch is in the opposite direction of a vehicle's collision force.
• PLASTIC BAGS
  • Due to the manufacturing process a plastic bag may be individualized back to the original box it came from. 
• EXPLOSIVES
  • Explosive substances can be examined to determine its chemical composition to identify the type of explosive used and its origin.
  • Traces of explosives found on a suspect's clothing, skin, hair, or other objects may be matched to explosives from the crime scene.
  • Materials used to make an explosive device will be compared to evidence found in the suspect's possession to confirm a match.
• FIREARMS 
  • Caliber (handguns & rifles) or gauge (shotguns) refers to the size of the internal diameter of a gun's barrel.
    
  • CLASSIFICATION - can determine the make of the gun by examining the bullet for the number of lands & grooves, direction of twist, and caliber. 
  • IDENTIFICATION - Rifling (grooves) in a gun barrel causes distinctive grooves, indentations and scratches upon fired bullets, which can be matched to the weapon that fired them. 
  • STRIATIONS RECONSTRUCTION - Chemical tests can reveal gunshot residue (GSR) on the hands, face, or clothing of a victim or suspect to indicate how close a person was to a fired gun.
• SOIL , DUST & DIRT
  • Dust, dirt, or sand evidence can reveal where a person has traveled and may be picked up at a crime scene or left behind.
  • Investigators examine the samples for chemical composition, pollen, plant material, and other organic matter to find links to a specific crime scene.
• FINGERPRINTS, LIP PRINTS 
  • CLASSIFY: arches, loops, and whorls.
  • INDIVIDUALIZE: unique ridge characteristics in a fingerprint (MINUTIAE)
  • AFIS: Automated Fingerprint Identification System is a database used by investigators at local, state, and national levels to search for matches to fingerprints found at a crime scene. How Fingerprints Work: Patterns & Triradii
• BODY FLUIDS
  • BLOOD, SEMEN, SALIVA, SWEAT, and URINE can be analyzed to give investigators information about the crime as well as its victim or the suspect.
  • Chemicals and UV LIGHT can be used at a crime scene to find body fluid evidence.
  • CLASSIFY – Species, Blood Type 
  • INDIVIDUALIZE - DNA
  • RECONSTRUCTION – Blood Spatter Analysis
• DRUGS and POWDER RESIDUES
  • CLASSIFY: Physical and Chemical properties used to identify what a substance is.
  • CANNOT INDIVIDUALIZE: but may have a signature formulation; making it very unique. 
  • TRACE ELEMENT ANALYSIS: Determine where drug originated from.
• DNA
  • INDIVIDUAL - Investigators can extract DNA from almost any tissue, including hair, fingernails, bones, teeth and body fluids. The DNA is used to create a profile that can be compared to profiles from suspects or victims.
  • CODIS (Combined DNA Index System) is a database maintained by the FBI that is used to find matches to unknown DNA samples from a crime scene.
• WOUNDS
  • Wounds can often be matched to weapons or tool marks on the weapon. Investigators may also be able to determine the weapon's size, shape, and length.
  • Analysis of a wound may provides clues to a victim's injuries, characteristics of the suspect (left-handed, right-handed, height, etc.), and positions of the victim and suspect at the time of the incident.
• Questioned Documents 
  • Examiners will analyze a ransom note or other document to find clues to link it to a crime scene or a specific suspect. They will analyze the type of paper used, printing method or handwriting style, and type of ink.
  • Other unique features, such as watermarks on stationary or indentations made as someone wrote on a page in a notebook
• HAIRS & FIBERS
  
  • Hairs and fibers may be transferred from the suspect or the suspects clothes to the victims' and vice versa. For example, a suspect may pick up carpet fibers on his shoes or leave hairs behind at a crime scene. 
  • HAIRS CLASSIFY - Hairs can be examined to identify their origin, such as human or animal. Forcefully removed or Naturally fell out. HIGH INTRASAMPLE AND INTERSAMPLE VARIATION. INDIVIDUALIZE - Hairs with roots intact can be tested for DNA. 
  • FIBERS CLASSIFY - type: cotton, wool, polyester, nylon, etc. Analyze dyes INDIVIDUALIZE, fit torn fabric together. 
• IMPRESSION EVIDENCE 
  • Shoe prints & Tire Tracks
    • Impression evidence can be photographed, lifted with tape, or cast with plaster to compare to a suspect's shoes or tires.
    • CLASSIFY: to identify the brand of shoe size or tire based on its tread pattern and other physical features to provide leads in the case. 
    • INDIVIDUALIZE: Shoes and tires will also show wear patterns after being used for a period of time as well as other features (scratches, nicks, and cuts) that can be used to match evidence to specific items. For example, shoeprints can be matched to a suspect based on how the treads on the shoes that are worn down due to that person's walking style. 
  • Bite Marks
    • INDIVIDUAL : Each of the 32 teeth in humans is unique due to age and wear. 
    • Impressions and photographs of bite marks left on a victim, assailant, or other object at a crime scene can often be matched to dental records.
      
  • Tool Marks 
    • INDIVIDUAL : Tiny nicks and chips form on the edges of a tool as it is used, which can be used to identify matches between evidence and suspects.
    • Tools may also pick up traces of blood or other substances that can be tested or have fingerprints that can be lifted.
      
• SKELETAL REMAINS 
  • CLASSIFY: to determine four characteristics for a victim: age, sex, race, and stature (height/build). 
    • Sex - Determined by examining the pelvis, humerus, and femur 
    • Age and stature – Determined by analyzing the development of the teeth, bone growth, and the length of specific bones, such as the femur 
      
  • INDIVIDUALIZE: DNA samples can be collected from bone, teeth, and hair to provide clues to a person's identity. Scientists may also be able to gain clues as to a person's past, recent injuries, or the cause of death based on bone fractures and other signs of trauma.