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Elements Of Forensic Science
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Elements Of Forensic Science


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  • 1. Elements of Forensic Science Types of Evidence Related Services
  • 2. Elements of Forensic Science
    • Firearms and Toolmark Identification
    • Forensic Psychiatry and Profiling
    • Questioned Document Examination
    • Criminal Law
    • Careers in Law Enforcement
    • Forensic Photography
    • Personal Identification
    • Crime Scene Processing
  • 3. Firearms and Toolmark ID
    • ballistics and bullet matching
      • each firearm has it’s own “signature” in the rifling in the barrel
        • lands and grooves spiral down the barrel
        • soft lead is forced into these areas creating microscopic scratches thus marking the bullet
  • 4. Firearms and Toolmark ID
    • ballistics and bullet matching
      • these scratches are unique to one particular firearm
      • tested in lab by firing a bullet through the suspect weapon
        • test fired bullet compared to crime scene bullet
        • if striations(scratches) line up – a positive match is made
        • if striations don’t line up, result is negative
  • 5. Firearms and Toolmark ID
    • ballistics and bullet matching
      • much debate about “ballistic fingerprinting”
        • barrels can be changed out completely or filed down
        • barrels and firing pins also wear with time changing the “fingerprint”
        • firing pins can be easily modified
  • 6. Firearms and Toolmark ID
    • imprint evidence
      • two types
        • three dimensional ex. car tire in mud
        • two dimensional ex stepping in paint
          • this type leaves two imprints – one in the paint (a negative image) and one from the bottom of the shoe onto a new surface (like a rubber stamp)
        • can be so detailed it can be used to identify class and individual characteristics
  • 7. Firearms and Toolmark ID
    • imprint evidence
      • tire impressions
        • tread evidence
        • pattern of long tire impression can yield additional information
          • wheel base distance
          • direction car facing
          • how they pulled out
          • direction of travel
  • 8. Firearms and Toolmark ID
    • toolmark identification
      • three types of toolmark impressions
        • compression – a tool surface presses into a softer material
        • sliding – a tool scrapes across a surface causing parallel striations
        • cutting – a combination of the two
      • all three types can yield class and individual characteristics
  • 9. Firearms and Toolmark ID
    • explosives
      • residue can be analyzed to determine type of explosive
        • some manufacturers are putting chemical tags in their explosives that allow for tracking of specific batches
      • detonator can be analyzed for origin of component parts
  • 10. Forensic Psychiatry& Profiling
    • forensic psychiatry
      • serves to define
        • what mental illness and disorder are
        • what creates mental illness and disorder
        • how they are diagnosed
        • how they are treated
  • 11. Forensic Psychiatry& Profiling
    • forensic psychiatry
      • mental illness – the individual does not function well because of emotional fluctuations or distorted point of view interpretation
      • mental disorder – clinically significant behavior or psychological syndrome or pattern that is associated with present distress or disability or with a significantly increased risk of suffering death, pain or disability or loss of freedom
  • 12. Forensic Psychiatry& Profiling
    • forensic psychiatry
      • issue of incompetency is fitness to stand trial
        • must understand what is going on
        • can help in their own defense
        • three bases of incompetency
          • emotional/psychological factors
          • cognitive or intellectual factors
          • physical factors
        • competency evaluation must be done – cannot be refused
  • 13. Forensic Psychiatry& Profiling
    • forensic psychiatry
      • issue of insanity applies to mental state of defendant at time at which the crime was committed
        • defendant must concede guilt at time of insanity plea
        • defendant must be competent to stand trial
        • defendant must prove profound defect of mental ability – this must be directly related to the crime
  • 14. Forensic Psychiatry& Profiling
    • profiling
      • process by which trained forensic psychologist sifts through aspects of the crime to develop a description of the personality of the perpetrator
      • “ Behavior reflects personality.” (John Douglas, Mindhunter )
      • process works because of extensive database
        • interviews of hundreds of convicted serial killers, serial rapists, and mass murderers
  • 15. Forensic Psychiatry& Profiling
    • profiling
      • description can include
        • age
        • sex
        • occupation
        • behavioral disorders
        • upbringing
        • marital status
        • type of living quarters and general condition
        • type of person the perpetrator lives with
        • what type of car is driven
        • any disability or difficulty in relating to others
        • how the crime was committed
  • 16. Forensic Psychiatry& Profiling
    • profiling
      • description can be used to
        • focus investigation on particular suspects
        • provide strategies on how to approach suspect during interrogation
        • provide strategies on how to break him down on the witness stand at the trial
      • Criminal Minds
  • 17. Questioned Document Analysis
    • handwriting analysis
      • examination of design, shape and structure
      • determine authorship
      • basic principle is that no two people will write the exact same thing in the exact same way
  • 18. Questioned Document Analysis
    • handwriting analysis
      • characteristics
        • letter formations
        • connectors
        • upstrokes
        • retraces
        • down strokes
        • spacing
        • baseline
        • curves
        • size
        • distortions
        • hesitations
        • flying stops
  • 19. Questioned Document Analysis
    • typewriting
      • much like firearms, typewriters of the same make and model are pretty much the same
      • daily wear and tear or parts of the machining process can cause “defects” or individual characteristics that translate to paper when the machine is used
  • 20. Questioned Document Analysis
    • photocopiers and laser printers
      • in photocopier, original is placed on glass and exposed using reflected light to a drum that is covered with photosensitve material
      • image of original exists on drum as invisible positive photoelectric charge
      • negatively charged toner is drizzled on drum where it sticks to the positive image
      • paper with a positive charge passes the drum causing the negatively charged toner to transfer to the paper which is then heat sealed
      • with laser printer - image of the original held in memory of computer is written to the photosensitive drum using a laser
  • 21. Questioned Document Analysis
    • photocopiers and laser printers
      • paper yields clues
        • marks from belts, pinchers, rollers and gears can be matched like toolmarks
      • toner
        • can have unique chemical compositions
        • how toner is placed and fused on paper (ie. clumps, blobs)
      • marks on optics
        • scratches or other marks on glass, lenses or mirrors will leave markings on the printed page that can be matched with the optic
  • 22. Questioned Document Analysis
    • forgery
      • false making or altering of any writing with intent to defraud
      • four types
        • traced
        • simulation
        • freehand
        • lifted
  • 23. Questioned Document Analysis
    • forgery
      • traced can use
        • overlays (like tracing paper)
        • transmitted light (as with a light board)
        • tracing indentations left in the page underneath the original
        • tracing patterns of dots that outline the writing to be forged
  • 24. Questioned Document Analysis
    • forgery
      • simulation
        • involves the copying of writing from a genuine article, trying to imitate the handwriting of the original
      • freehand
        • written with no knowledge of the appearance of the original
        • just writing off the top of your head and passing it off as something else
  • 25. Questioned Document Analysis
    • forgery
      • lifted
        • tape is used to lift off a signature then place it on another document
      • detection of forgeries
        • freehand easiest to detect
        • simulation easy to detect – style not as fluid, more hesitations than “comfortable” writing
        • traced and lifted are easy to detect but identity of forger cannot be determined
  • 26. Questioned Document Analysis
    • counterfeit security measures
      • U.S. currency
        • easy to counterfeit!
        • all paper currency after 1993 has microline printing, nylon security threads and a plastic security strip
        • as of 2000, all paper currency was updated except the $1 bill
  • 27. Questioned Document Analysis
    • counterfeit security measures
      • official documents (i.e. passport)
        • background is printed with intricate pattern of polygons with a color shift in the ink
        • green stars – reflective specks sealed in the paper
        • blue “USA” stamp overlaps photo and background paper
        • three red stars stamped over edge of photo
        • whole page sealed with single sheet of adhesive plastic
        • microline printing in lower right corner
  • 28. Criminal Law
    • serves to define offences under a codified system of laws and punishments
    • where we define what crime is and how it goes about being prosecuted
  • 29. Criminal Law - Homocide
    • murder (malice required)
      • first degree
        • intentional and premeditated killing
        • killing in the course of a dangerous felony
      • second degree
        • intentional, but not premeditated
        • intent to cause serious bodily injury resulting in death
        • death by act creating grave risk of death
        • killing in the course of other mala in se felonies
  • 30. Criminal Law - Homocide
    • manslaughter (no malice required)
      • voluntary
        • killing with the intent to kill or inflict grievous bodily injury but under the influence of passion caused by sufficient provocation
      • involuntary
        • negligent or reckless homocide
        • killing in the course of committing a dangerous misdemeanor
  • 31. Criminal Law - Homocide
    • justifiable homocide
      • self defense
      • defense of others
      • defense of property
      • prevention of felonies
      • arresting a felon
  • 32. Criminal Law - Homocide
    • accidental death
      • duty of care
      • involuntary manslaughter or negligence
  • 33. Criminal Law – Assault and Battery
    • battery
      • intentional or reckless touching of another without excuse or justification
      • does not require significant blow that inflicts bodily injury
  • 34. Criminal Law – Assault and Battery
    • assault
      • an unlawful attempt, coupled with present ability, to commit a battery (such as a missed punch)
  • 35. Criminal Law – Assault and Battery
    • aggravated assault and battery
      • when battery inflicts a serious bodily injury or assault and battery involves the use of a deadly weapon
      • assault with intent to rape
  • 36. Criminal Law – Rape
    • sexual intercourse by a male with a female, who is not his wife, achieved by force or threat of force against the will of the victim
      • force can include drugs administered by the male OR inability of the victim to understand what is happening
      • spousal “immunity” in some old laws has been done away with
      • men don’t rape men – they sodomize
      • women may be charged with rape as a accomplice, (this too is changing)
  • 37. Criminal Law – Rape
    • statutory rape involves sexual intercourse with a minor who is regarded by law as incapable of giving lawful consent to the act
  • 38. Criminal Law – Conspiracy
    • agreement between two or more people, beyond an undercover government agent, to commit an unlawful act, and some degree of intent
      • ultimate act can be impossible to carry out
      • everyone does not have to know everyone else involved
      • all parties must have a common end
      • acts of one are acts of all
  • 39. Criminal Law – Conspiracy
    • for conspiracy, one overt act in furtherance of the crime by any involved party gives liability
      • if one abandons the conspiracy, he is still liable for the conspiracy, but not the resulting act
      • “ overt act” need not be criminal in itself
    • individuals are charged with conspiracy and the actual crime (i.e. murder), the two don’t merge
  • 40. Criminal Law – Burglary
    • at common law, breaking and entering into a dwelling during the night with intent to commit a felony
      • modern code includes
        • any building or similar structure
        • day or night
        • unlawful entry
        • with or without a breaking
      • people get robbed, not houses
  • 41. Criminal Law – Larceny
    • taking the property of another, with knowledge of their ownership, to deprive them permanently or infringe upon their rights in a substantial way
      • petit vs. grand larceny varies in $$$ amount of property
      • one cannot negligently steal
  • 42. Criminal Law – Embezzlement
    • persons who lawfully received possession of the property of another and then wrongfully convert that property to their own use
      • real property can be embezzled
      • does not require intent to permanently deprive
  • 43. Criminal Law – False Pretenses
    • applies to persons who induce others to transfer property to them by means of misrepresentation, which must be to a material past or present fact that the seller know to be false
      • does not include “seller’s talk”
  • 44. Criminal Law – Robbery
    • a larceny with the stolen property taken from the victim in the presence of the victim and with the taking accomplished by means of force or threat of force
      • crime against person and property
    • Does pickpocketing constitute a robbery?
  • 45. Criminal Law – Extortion
    • threat of force or harm used to achieve some sort of benefit to the criminal
      • truth can be used as leverage
      • benefit does not have to be monetary
      • “ blackmailing”
  • 46. Criminal Law – Arson
    • an intentional or reckless burning or explosion of a building owned by another person or, under limited circumstances, of a building owned by the actor
  • 47. Criminal Law – Solicitation
    • agreement to commit a crime
      • hiring individual is just as liable as the actor
      • merges into conspiracy
  • 48. Criminal Law – Aiding and Abetting
    • involved prior to the crime, contributed to the act or induced the act, even if not involved in the act itself
      • one who orders a crime shares the same liability as the actor
  • 49. Careers in Law Enforcement
    • federal law enforcement
    • state agencies
    • city agencies
    • local agencies
    • private sector
  • 50. Careers in Law Enforcement
    • types of jobs
      • investigators, officers, troopers
      • lab positions
      • support positions (clerks, evidence technicians, surveillance operations, photographers)
    • education necessary
      • depends on job description and agency
      • usually college degree to start
      • specialization in a field might be required
  • 51. Careers in Law Enforcement
    • typical application process
      • call agency’s personal department and ask for an application
      • send in and get called for initial interview
      • written exam – much like SAT’s
      • background questionnaire and check
      • panel interview
      • physical
      • fitness test (if in the field)
      • polygraph test