CIS205 Forensic Statistics

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CIS205Forensic Statistics

• Michael.Oakes_at_sunderland.ac.uk
• Room 224A, Extension 3631
• Module Web Site osiris.sunderland.ac.uk/cs0moa/f
  orensic.htm

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Aims and Objectives

• Knowledge of different data from laboratory
  experiments.
• Understanding of statistical techniques used to
  examine forensic data.
• Understanding of evaluation of forensic evidence.
• Apply appropriate statistical techniques for
  specific classes of forensic data.
• Program using R.

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Recommended Books

• David Lucy, Introduction to Statistics for
  Forensic Scientists, Wiley, 2005.
• John Verzani, Using R for Introductory
  Statistics, Chapman Hall / CRC, 2005.

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Assessment

• The assessment strategy will employ an
  examination to assess fundamental knowledge of
  the material covered by the module and one piece
  of individually designed coursework based upon
  one area of the course of study. The assignment
  will include a small research component.
• In order to pass the module you must obtain an
  average overall mark of 40 or greater across the
  two assessments.
• If you are unsuccessful in passing the module,
  the Board of Assessment may at their discretion
  refer you in those elements in which you were
  unsuccessful, if it is convinced that you have
  made a genuine attempt to engage with the module.
  Alternatively, you will have to repeat the
  module.

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The importance of forensic statistics

• Forensic statistics is the application of
  statistics to forensic science and the law.
• Forensic statisticians help to quantify evidence
  in criminal cases

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Forensic statistics

• Statistics are becoming increasingly important
  within forensic sciences.
• There is an increasing demand for the
  quantitative substantiation of (un)certainties
  and margins in measurements and interpretations.
• Also the strength of evidence and conclusions in
  the forensic context are of much interest.
• Forensic statistics supports other areas of
  expertise, but a trend can be observed in viewing
  it as an independent area of expertise.

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Forensic science

• The analysis of traces of evidence (such as body
  fluids, glass fragments, footprints and drugs)
  left at the scene of a crime by the criminal,
  victim or others.
• This evidence may be used subsequently to either
  implicate or exonerate a person suspected of
  committing that crime, or just to gain further
  insight into the incident.

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Evidence

• But forensic science doesn't just involve
  identifying traces of evidence sometimes it
  isn't obvious just what a piece of evidence
  really is.
• Other important questions that need to be
  answered are just how the evidence came to be at
  the crime scene, where did it originally come
  from, and who left it there.
• This suggests a natural role for statistics, as
  these questions can typically only be answered in
  terms of probabilities.
• So it is not surprising that the primary task of
  forensic statisticians is to evaluate any
  evidence found at a crime scene, so that this
  evidence can be appropriately presented to a jury
  in court.

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DNA profiling

• The advent of DNA profiling in the 1980s brought
  a big change in the way the legal system viewed
  quantitative data.
• Now a quantitative approach is being requested in
  many areas, far removed from the original area of
  DNA profiling.
• The earlier research and development work is
  being applied and further work is being done to
  tackle the increasingly more complex cases which
  arise in bringing a sound statistical approach to
  the assessment of evidence.

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Probability

• For an appropriate evaluation of evidence, a
  comparison of probabilities of the evidence under
  two different propositions is required.
• These propositions are usually those put forward
  by the prosecution and the defence.
• There are advanced statistical methods for doing
  this (based on likelihood ratios or Bayes'
  factors)
• Much theoretical work has been done in the
  development of these methods.
• Calculations based on them might sometimes be
  fairly straightforward, though it also often
  turns out that there are non-standard issues to
  consider.
• Fallacies

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Example of casework

• DNA profiling evidence for biological material
  such as bodily fluids.
• Statistical and population genetics to assess the
  importance of such evidence.
• Never just one sample of DNA and one suspect.
• Relatives may be involved
• Suspect may have been identified by DNA profile
  database search
• Mixture of body fluids from more than one person.
  
• More advanced statistical methods are required in
  such situations

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Sampling problems

• Another role of a forensic statistician relates
  to sampling problems and determination of sample
  size.
• Examining a consignment of similar-looking items
• Often not practical to examine every item.
• Financial or health grounds
• E.g. set of CDs, some of which are thought to
  contain pornographic material.
• How many items should be examined on a sampling
  basis?
• As few CDs as is commensurate with a good
  description of the proportion of the CDs which
  are illicit.
• The sample size determination is really just a
  quality control problem there are UN Guidelines
  where the problem concerns drugs.

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Expert witnesses

• Communicate results effectively to
  non-statisticians.
• Forensic statisticians are often required to
  attend court cases as "expert witnesses".
• This involves reporting calculated probabilities,
  or other statistical measures, to the jury, and
  explaining to them how the calculations were
  performed.
• Choose careful wording
• Dont "lead" the jury into a decision on guilt or
  innocence of a defendant

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forensischinstituut.nl

• http//www.forensischinstituut.nl/NFI/en/Typenond
  erzoek/Items/Forensicstatistics.htm
• RD
• Random testing of narcotics, hairs, textile and
  environmental investigation
• Development of an uncertainty analysis for
  reconstructing a speed of impact in traffic
  accidents
• Classification and individualisation of
  earprints, traces of scratches and imprints,
  faces and spectra
• Use of databases
• Interpretation of evidence
• Combining conclusions (with uncertainties) in
  sub-investigations into a summarised final
  conclusion
• Interpretation and conclusions in DNA
  identification
• Investigation into the use of probability scales
  in the formulation of conclusions
• Use of Bayes theorems and methods in legal
  evidence
• Uncertainties that are created in the
  interpretation and analysis of photos and video
  images

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Forensic subjects

• (ENVIRONMENTAL) ANALYSIS
• (WASTE) MATTER BUILDING MATERIALS AND EMISSIONS
• DIGITAL TECHNOLOGY
• DNA ANALYSIS
• DNA PARENTAGE TESTING
• DOCUMENT EXAMINATION
• DRUGS ANALYSIS
• ECOLOGICAL AND HUMAN TOXICOLOGY
• EMBEDDED SYSTEMS
• ENVIRONMENTAL CRIME SCENE INVESTIGATION
• ENVIRONMENTAL FORENSICS
• EXAMINATION OF SURFACE MARKS, IMPRESSIONS AND
  SHAPES
• FIBRES AND TEXTILE INVESTIGATION
• FINGERMARK IDENTIFICATION

• FORENSIC EXAMINATION OF HAIR
• FORENSIC EXPLOSIVES INVESTIGATION
• FORENSIC INVESTIGATION OF FIRE
• FORENSIC PHOTOGRAPHY
• FORENSIC STATISTICS
• GUNSHOT RESIDUE INVESTIGATION
• HANDWRITING EXAMINATION
• ILLICIT DRUG PRODUCTION
• IMAGE ANALYSIS AND BIOMETRY
• INVESTIGATION OF THE TECHNICAL CAUSE OF FIRE, AND
  ANALYSIS OF TECHNICAL APPLIANCES AND MATERIALS
• INVESTIGATION OF WEAPONS AND AMMUNITION
• MACHINE AND PRINTER TYPE ANALYSIS
• OPEN SYSTEMS
• PATHOLOGY
• SOIL, WATER AND FERTILISERS
• SPEECH AND AUDIO ANALYSIS
• TOXICOLOGY
• TRAFFIC ACCIDENT INVESTIGATION
• VEHICLE IDENTIFICATION INVESTIGATION

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History of Forensic Science

• Both old and young field
• The "Eureka" legend of Archimedes (287-212 BC)
  can be considered an early account of the use of
  forensic science.
• In this case, by examining the principles of
  water displacement, Archimedes was able to prove
  that a crown was not made of gold (as it was
  fraudulently claimed) by its density and
  buoyancy.

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Washing Away the Wrongs

• The first written account of using medicine and
  entomology to solve (separate) criminal cases
• 1235 Sung Tzu solved a murder by instructing all
  suspects to bring their sickles to one location.
  Flies, attracted by the smell of blood,
  eventually gathered on a single sickle. In light
  of this, the murderer confessed.
• The book also offered advice on how to
  distinguish between a drowning (water in the
  lungs) and strangulation (broken neck cartilage).

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Identification of remains (odontology and
anthropometry)

• 1447 Missing teeth of French Duke of Burgandy
  used to identify body
• 1776 False teeth of US General Warren used to
  identify his body
• 1849 Bones and teeth used as evidence for murder
  victim
• 1879 System of measuring people by body
  measurements developed by Bertillon of France
• 1940s Dental records and teeth from corpse were
  compared
• 1957 Skeletal growth stages developed by Mocker
  and Stewart

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Early Pathology

• In sixteenth century Europe, medical
  practitioners in army and university settings
  began to gather information on cause and manner
  of death.
• Ambrose Paré, a French army surgeon,
  systematically studied the effects of violent
  death on internal organs.
• Two Italian surgeons, Fortunato Fidelis and Paolo
  Zacchia, laid the foundation of modern pathology
  by studying changes which occurred in the
  structure of the body as the result of disease.
• In the late 1700s, writings on these topics began
  to appear. These included "A Treatise on
  Forensic Medicine and Public Health" by the
  French physician Fodéré, and "The Complete System
  of Police Medicine" by the German medical expert
  Johann Peter Franck.

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Weapons identification

• 1784, in Lancaster, England, John Toms was tried
  and convicted for murdering Edward Culshaw with a
  pistol. When the dead body of Culshaw was
  examined, a pistol wad (crushed paper used to
  secure powder and balls in the muzzle) found in
  his head wound matched perfectly with a torn
  newspaper found in Toms' pocket.
• 1889 Bullets were matched to gun they were fired
  from, advent of ballistics

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Father of toxicology

• 1814 Scientific paper on poison published by
  Matthieu Orfila of Spain
• the first person to systematise the study and
  classification of toxic substances when he found
  traces of poison in the liver of a dead dog.

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Arsenic Detection 1836, Marsh

• Arsenic was popular poison since arsenic trioxide
  is tasteless and easily dissolved.
• suspect fluid would be mixed with sulfuric acid
  (H2SO4) and passed through a U-shaped tube with a
  piece of arsenic-free zinc at the end. If even a
  trace of arsenic was present, arsine (AsH3) gas
  would result.
• As2O3 6 Zn 6 H2SO4 ? 2 AsH3 6 Zn(SO4)2 3
  H2O
• When ignited the arsine gas would first
  decompose into arsenic trioxide and hydrogen.
  When he held a cold ceramic bowl, the arsenic
  would form a silvery-black deposit on the bowl
  due to reduction by carbon
• 2 As2O3 3 C ? 3 CO2 4 As
• Not only could minute amounts of arsenic be
  detected (for as little as 0.02 mg), the test was
  very specific for arsenic.

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Fingerprinting

• 1628 Birth of Italian Marcello Malpighi, first
  to notice patterns of skin on fingers is distinct
• 1823 Whorls, ellipses, and triangles identified
  by Jan Evangelista Purkinjie
• 1880 Fingerprints used by Henry Fauld to
  identify criminals
• 1892 Scientific classification of fingerprints
  developed by Galton

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Fingerprinting (contd)

• 1896 System of matching fingerprints to identify
  people developed by Ed Henry
• 1900 Scotland Yard adopts the Henry system of
  fingerprinting
• 1902 First person was convicted on fingerprint
  evidence
• 1903 NYC police began fingerprint files of
  arrested persons
• 1930 National fingerprint file set up by FBI
• 1960 First laser design to identify fingerprints
  was developed

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Technology

• 1590 Microscope developed
• 1670 First powerful microscope created by Anton
  Van Leeuwenhoek
• 1732 Luigi Galvani discovered human nervous
  system transmits information electronically
• lie detector test
• 1859 Spectroscopy was developed
• 1888 Hand held camera invented by Eastman
• 1921 First lie detector built by Larson, USA
• 1971 Photo-fit software enables witness to piece
  together facial features
• 1978 ESDA (electrostatic document analysis)
  developed document impressions

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Blood-typing and DNA analysis

• 1901 Human blood groups were identified by Karl
  Landsteiner
• 1909 Chromosomes discovered to carry hereditary
  information
• 1980 Method for detecting DNA differences
  developed
• 1984 Genetic profiling using DNA was developed
  by Jeffries
• 1987 First time DNA evidence was used to convict
  a person in the US

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Organizations

• 1807 Forensic Science Institute opened at the
  Univ. of Edinburgh, Scotland
• 1910 First forensic laboratory opened in France
  by Edmond Locard
• 1932 FBI forensic laboratory established
• 1967 FBI National Crime Information Center
  Established
• 1981 FBI Forensic Science Research and Training
  Center opened