Chemistry

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An in-depth look at the research and chemistry side of investigating crimes.

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Chemistry

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

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