Chemistry

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Chemistry - Presentation Transcript

    • Chemistry
    Forensics Physics Biology
  1. Chemistry The study of composition, structure, properties, and reactions of a substance which help us identify a suspect.
  2. Table of Contents
    • 2- Biology
    • 2.1: Forensic Autopsies
    • 2.2: Blood Testing
    • 2.3: Biological Fingerprinting
    1- Chemistry 1.1: Chemiluminescent Substrates 1.2: Latent Print Identification 1.3: Scanning Kelvin Probes 3- Physics 3.1: Ballistic Fingerprinting 3.2: Ballistic Microstamping 3.3: Firearm Identification
  3. Biology The study of the investigation of living matter, or once living matter, in reference to its origin, behaviour, and classification.
  4. Table of Contents
    • 2- Biology
    • 2.1: Forensic Autopsies
    • 2.2: Blood Testing
    • 2.3: Biological Fingerprinting
    1- Chemistry 1.1: Chemiluminescent Substrates 1.2: Latent Print Identification 1.3: Scanning Kelvin Probes 3- Physics 3.1: Ballistic Fingerprinting 3.2: Ballistic Microstamping 3.3: Firearm Identification
  5. Physics The study that comprises of all investigations that deal with motion, force, and dynamics.
  6. Table of Contents
    • 2- Biology
    • 2.1: Forensic Autopsies
    • 2.2: Blood Testing
    • 2.3: Biological Fingerprinting
    1- Chemistry 1.1: Chemiluminescent Substrates 1.2: Latent Print Identification 3.2: Scanning Kelvin Probes 3- Physics 3.1: Ballistic Fingerprinting 3.2: Ballistic Microstamping 3.3: Firearm Identification
  7. Chemiluminescent Substrates
    • Light emitted due to a chemical reaction where it is an intermediate state; does not last long
    • E in Reactants > E in products; The decay of the intermediate state results in the emission of light
    • Used during criminalistics as luminols for tracing blood
    1.1
  8. Luminols
    • React with oxidizing agent to emit a neon blue colour (lasts 30 seconds)
    • Detect trace amounts of blood (even after being cleaned/removed) using H 2 O 2 where Fe 2+ (from hemoglobin) becomes a catalyst
    • luminol + H 2 O 2 -> 3-APA + excess energy -> 3-APA + light
    • May react with oxygen present in copper, bleaches, urine
    1.1
    • Latent fingerprints occur when natural secretions of the skin are deposited on a surface through contact; not readily visible
    • Chemical reactions (reagents) are used to reveal hidden chemicals in fingerprints and increase visual contrast
    • Iodine, like all halogens, is a good oxidizing agent. Oils from skin, which allow the fingerprint to be created in the first place, are the victims of oxidation
    • Solid iodine sublimates (solid -> gas)when exposed to room temperature
    • AgNO 3(aq) + NaCl (aq) -> NaNO 3(aq) + AgCl (s)
    Latent Print Identification 1.2
  9. Latent Print Identification 1.2
  10. Benazir Bhutto
    • Medical report released with an open letter on inconclusiveness
    • The amount of blood in the area prevented the FBI from a thorough crime scene investigation
    • Law enforcement agencies cited Islamist Web sites as saying al-Qaida had claimed responsibility through an unauthorized official
  11. Forensic Autopsies
    • Thorough examination of a corpse
    • Determines manner and cause of death, state of person’s health before death, if medical diagnosis was appropriate before death
    • Criminal cases do not require consent from next of kin;
    • Performed by a pathologist
    2.1
    • View & Grant Procedure: Body photographed; samples of hair, nails taken; body searched using UV light or radiographic image; wounds examined; general description recorded
    • Internal: Incisions are made down the chest, extended to navel; shears are used to open cavity; organs & major blood vessels are removed and examined and weighed
    • Limbs and face not usually examined internally
    • Body is reconstituted by sewing after being lined with cotton wool-like material
    Forensic Autopsies (Procedure) 2.1
  12. Blood Testing
    • Analysis of sample of blood extracted from crime scene
    • Determine composition, organ function, and other biochemical and physiological properties
    • Physical analyses include metabolic measures of chemicals usually present in blood
    • Cellular analyses include blood typing, blood count, hematocrit, and DNA testing
    • Reveal connection to victim, or crime scene
    • May reveal cause/manner of death of victim depending on case
    2.2
  13. Blood Testing 2.2
  14. Fingerprinting 2.3
    • Fingerprints are either patent or latent where the ridges of a fingertip are impressed on a surface
    • Patent fingerprints are easily revealed; latent ones are harder to pinpoint
    • Iodine can only be used for fresh fingerprints
    • Other substances are not as effective, such as silver nitrate (AgNO 3 )
    • Scanning Kelvin Probes is a new technology that is non-contact; allows for the retention of all material; they are not currently is use
    • SKPs measure the voltage at pre-set intervals on surface where fingerprint may be deposited
    • Measurements mapped to produce 3D image
    • Physical removal of fingerprint does not result in loss of entire information of fingerprint: inorganic salts in deposit make metal-ion complexes
    • Requires very low points/mm frequency; is very efficient
    • Can only be on metallic or electrically-conductive material
    Scanning Kelvin Probes 2.3
  15. Benazir Bhutto
    • doctors had tried for 35 minutes to resuscitate Ms. Bhutto
    • Dr. Mohamed Mussadik said she was clinically dead on arrival
    • Apparently, no autopsy was done, because the “police chief prevented it”
    • a medico-legal report based on a mandatory post-mortem examination is a must in a murder case
    • The cause of death was reported as “Open head injury with depressed skull fracture”
  16. Ballistic Fingerprinting
    • Firearm examination that helps pinpoint the firearm used in a crime
    • Matches ballistic striae from the bullet with rifled barrel; matches marks on cartridge with marks in chamber and breech
    • Every bullet is marked with a specific “fingerprint” from the barrel when shot, therefore allowing for comparisons
    • However, barrels may be replaced inexpensively making this type of testing inefficient
    3.1
    • Aids firearm identification by engraving marking (make, model, and serial number) on firing pin and breech face using laser technology
    • When shot, pressure transfers marking to primer and cartridge case
    • After tracking to last retail owner, law enforcement can track illegal trade in guns
    • Low cost, and highly reliable
    Ballistic Microstamping 3.2
    • Looking at the wound from a bullet usually identifies gun model if polygonal rifling is not used; velocity can also determine type of gun
    • Impacts of bullets from slightly different velocities can affect wound, and therefore be identified
    • Each model of a gun has a different velocity (easily determined by a distance/time graph) which are logged by law enforcement
    Firearm Identification 3.3
  17. Firearm Identification 3.3
  18. Benazir Bhutto
    • Was shot in the neck/head, according to different accounts
    • Immediately after, suicide bomber detonated his bomb damaging one of the cars in her motorcade
    • Witnesses described seeing a sniper in nearby building
  19. References
    • NY Times: Bhutto Assassination
    • Huffington Post: Bhutto Autopsy
    • CSGV: Microstamping
    • Foxnews: How Reliable is Ballistic Fingerprinting
    • KelvinProveINFO: SKP
    • Death Online: Autopsy Procedure
  20. Forensics Chemistry Physics Biology

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