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Introduction to Forensic Science

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The PowerPoint file used in class on 25, 28 and 29 November, 2016.

Introduction to Forensic Science

  1. 1. Dr. Sangeetha Balakrishnan PG Department of Chemistry Women’s Christian College Chennai – 600 006 Forensic Science PCH/NM/01 25 November, 2016
  2. 2. What is Forensic Science? ‘Forensic’ – Latin forensis – “of a forum, place of assembly” Forensic science is the application of science to matters of criminal and civil law. An applied science; multidisciplinary and multidimensional in nature. The nature of science – no absolute authoritative solutions; all it offers is objective information on what occurred at a crime scene.
  3. 3. Forensic Science – The Concept • Based on Locard’s Principle of Exchange. • Whenever two objects – animate or inanimate, microscopic or macroscopic, in whichever physical state – come in contact with each other, there would be an exchange of materials. These materials are known as the Physical Evidence. • Forensic science essentially deals with the laboratory examination of different types of physical evidence, encountered at the scene of crime. • Physical evidence preferred over human witness.
  4. 4. Physical Evidence
  5. 5. Examples of Physical Evidence Imprints Broken glass Hairs Fibers Paint chips Documents Fingerprints Other prints (shoe, tire, etc.) Body/corpse Toolmarks/firearms Bullets/casings DNA Blood Semen Drugs, chemicals Soil
  6. 6. The History and Development of Forensic Science
  7. 7. Sir Arthur Conan Doyle  Published first novel, A Study in Scarlet, 1887.  "I've found it! I've found it," he shouted to my companion, running towards us with a test-tube in his hand. "I have found a re-agent which is precipitated by haemoglobin, and by nothing else . . . . Why, man, it is the most practical medico-legal discovery for years. Don't you see that it gives us an infallible test for blood stains? . . . . The old guaiacum test was very clumsy and uncertain. So is the microscopic examination for blood corpuscles. The latter is valueless if the stains are a few hours old. Now, this appears to act as well whether the blood is old or new. Had this test been invented, there are hundreds of men now walking the earth who would long ago have paid the penalty of their crimes. . . . Criminal cases are continually hinging upon that one point. A man is suspected of a crime months perhaps after it has been committed. His linen or clothes are examined and brownish stains discovered upon them. Are they blood stains, or mud stains, or rust stains, or fruit stains, or what are they? That is a question which has puzzled many an expert, and why? Because there was no reliable test. Now we have the Sherlock Holmes's test, and there will no longer be any difficulty." → had a considerable influence on popularising scientific crime-detection methods
  8. 8. 1) The Chinese book Hsi Duan Yu (The Washing Away of Wrongs), which appeared in 1248, provided the first association of medicine and law. The book offered useful advice such as distinguishing drowning (water in the lungs) and strangulation (pressure marks on the throat and damaged cartilage in the neck) from death by natural causes.
  9. 9. 2) Mathieu Orfila (1787-1853) One of the first celebrated cases in forensic science involved the 'father of toxicology', Mathieu Orfila (1787-1853), who worked in Paris and testified in an arsenic poisoning criminal trial in 1840. Orfila and others had developed a chemical test to detect arsenic, the poison of choice for the period because the symptoms, violent stomach pains and vomiting, were similar to cholera (a common disease of the times) and often went undetected.
  10. 10. 3) Alphonse Bertillon (1853-1914) Alphonse Bertillon's (1853-1914) personal identification system using a series of body and facial measurements for individualization. First ID system (so to speak)! Anthropometry.
  11. 11. 4 )Francis Galton (1822 – 1911) Conducted the first definitive study of fingerprints and their classification. 1892 – Treatise entitled Finger Prints.
  12. 12. 5) Leone Lattes (1887 – 1954) Devised a simple procedure for determining the blood type (A,B,O,AB) of a dried bloodstain in 1915. Karl Landsteiner discovered blood groups in 1901.
  13. 13. 6) Calvin Goddard (1891 – 1955) Used a comparison microscope to determine if a bullet was fired from a specific gun. Published study of “tool marks” on bullets. Father of Ballistics.
  14. 14. 7) Albert S. Osborn (1858 – 1946) Developed fundamental principles of document examination. 1910 – Treatise Questioned Documents. Was responsible for the acceptance of documents as scientific evidence by the courts.
  15. 15. Forensic Labs in India
  16. 16. Forensic Labs in India The Central Forensic Science Lab (CFSL) in Hyderabad. There are four central forensic laboratories in India: Hyderabad, Kolkata, Chandigarh, and New Delhi. CFSL Hyderabad is a centre of excellence in Chemical Sciences. CFSL Kolkata (oldest laboratory in India) in Biological Sciences and CFSL Chandigarh in Physical Sciences. These laboratories are under the control of the Directorate of Forensic Science (DFS) of the Ministry of Home Affairs.
  17. 17. Forensic Labs in India… cont’d. Around 26 well-established forensic science labs; mostly in the state capitals. Many states have regional forensic science labs in some districts under the supervision of the state forensic lab. Mobile Forensic Units – When evidences are too bulky to transport, or when a rapid analysis of the evidence becomes mandatory, mobile forensic units are sent to the scene of crime. These units house mini laboratories to carry out on the spot analyses, which might aid in the further investigation process.
  18. 18. The Organisation of a Forensic Science Laboratory
  19. 19. Headed by a scientist designated as Director; assisted by scientists at different levels – Deputy Directors, Assistant Directors, Scientific Officers and technicians. Generally the lab is divided into divisions headed by Deputy Directors or an Assistant Director. All officers of the lab are empowered to undertake examination of case exhibits and submit reports to the court through the Director.
  20. 20. The Units in a Forensic Lab 0) Case Receipt Unit - Taking over of case exhibits and handing over reports. - The sealed parcels are accepted after examining seals, the condition of the packet and the forwarding letter. - Sample in the parcel sent to appropriate divisions for analyses. - After lab examinations, the leftover portions of the samples are forwarded to this unit to be returned to the police.
  21. 21. 1) Biology Division Deals with biological materials like blood, semen, saliva, hair etc. Also undertakes examination of skeletal remains to find out species of origin, race, sex, age, stature of the bio materials. Identifies dried bloodstains and body fluids Compares hairs and fibers Identifies and compares botanical materials such as wood and plants
  22. 22. 2) Serology Division Created as a result of the ever increasing load of serological examinations. Responsible to find out the species of origin, blood group substances, enzyme, serum protein etc in the biological materials such as blood, semen, saliva, epithelial cells, tissues, bones, hairs, teeth cavity scrapings etc. DNA profiling done here.
  23. 23. 3) Chemistry Division Carries out chemical analysis; both qualitative and quantitative .  adulterated petroleum, fertilisers, medicines, burnt remains etc. 4) Toxicology Division Undertakes chemical analysis of all materials related to suspected poisoning; stomach wash, vomit, injection site etc.
  24. 24. 5) Physics Division Analyses building materials like adulterated cement samples, cement-sand proportions, strength of building materials etc. Analysis of glass, sand, soil, paint, dirt etc. Tool and cut mark identification, restorations of obliterated marks/writings/numbers etc. 6) Prohibition and Excise Division Analyses samples of spurious and illicit liquors, alcoholic beverages, blood alcohol level etc.
  25. 25. 7) Narcotics Division Samples of all narcotic drugs and psychotropic substances are sent to this division for analysis. Also analyses precursor chemicals used for manufacturing drugs and psychotropic substances. 8) Document Examination Unit Provides the skills needed for handwriting analysis and questioned document issues. Also analyses paper and ink, indentations, obliterations, erasures, and burned or charred documents.
  26. 26. 9) Ballistics/Firearms Division Identification of firearms Live/fired ammunitions Distance of fire Correlation between the ammunition and the firearm Gunpowder residue analysis 10) Explosive Division Analysis of chemical nature of material used in an explosion.
  27. 27. 11) Photography Unit Examines and records physical evidence at the crime scene and at suspects' locations 12) Latent Fingerprint Unit Processes and examines evidence for latent fingerprints i.e. those found on surfaces 13) Polygraph Unit Uses lie detectors, an essential tool of the crime investigator rather than the forensic scientist 14) Voiceprint Analysis Unit Involved in cases of telephone threats or tape-recorded messages Investigators may be able to connect a voice to a particular suspect
  28. 28. Other Forensic Services  Forensic Pathology Involves the investigation of unnatural, unexplained or violent death. The forensic pathologist may conduct an autopsy. After a human body expires, there are several stages of decomposition.  Rigor Mortis – shortening of muscle tissue; stiffening of body parts. Occurs within the first 24 hours, and disappears within 36 hours.  Livor Mortis – results in settling of blood in areas of body closest to ground. Begins immediately on death, and continues upto 12 hours.  Algor Mortis – results in the loss of heat by a body. Beginning about an hour after death, the body loses heat by 1 to 1.5 degrees F. per hour until the body reaches the environmental temperature. A medical examiner when presented with the body, will take its core temperature. Normal body temp = 98.6 degree F. If the deceased body temp = 85 degree F, then time since death between 9 and 14 hours.
  29. 29. Other Forensic Services Forensic Pathology …cont’d.  Potassium levels in the occular fluid also help determine the time of death. Cells within the eyes release K at a certain rate, and samples are taken for analysis.  Also, during autopsy, the amount of food in the stomach can also give an idea of the time of death.
  30. 30. Other Forensic Services Forensic Anthropology: Primarily involves the identification and examination of skeletal remains, in order to determine if the remains are human or another type of animal. If human, ethnicity, sex, approximate age, and manner of death can often be determined by an anthropologist. A forensic anthropologist may also help to recreate the face to aid in identification.
  31. 31. Other Forensic Services Forensic Entomology The study of insects and their developmental stages Can help to determine the time of death by knowing when those stages normally appear in the insect's life cycle The specific insects present in the body and the stage of development of fly larvae give an idea of how long the body has been left exposed. Environmental influences, such as geographical location, climate and weather conditions must be taken into account.
  32. 32. Other Forensic Services Forensic Psychiatry The study of human behavior and legal proceedings in both civil and criminal cases In civil and criminal cases, competency often needs to be determined In criminal trials, the evaluation of behavior disorders is often required in order to establish the psychological profile of a suspect.
  33. 33. Other Forensic Services Forensic Odontology Involves using teeth to identify victims when the body is left in an unrecognisable state. Tooth enamel resists decomposition, and outlasts even skeletal remains. The characteristics of teeth are specific to each individual. A forensic odontologist also investigates bite marks.
  34. 34. Evidence
  35. 35. Evidence The definition depends on who you ask! Legal: That which tends to support something or show that something is the case. When lawyers talk about the admissibility of evidence in court, they refer to its relevance (pertinence to the case) and its materiality (that it tends to prove something). Forensic Science: Evidence is anything that would make an issue more or less likely than it would be without the evidence. Everyday terms: Evidence is anything that tends to prove or disprove anything.
  36. 36. Different Types of Evidence 1. Physical vs. Non Physical 2. Real vs. Demonstrative 3. Known vs. Unknown 4. Individual vs. Class
  37. 37. Physical vs. Non Physical Evidence Physical Evidence consists of objects or things (obtained from a scene of crime). Non physical evidence is verbal testimony about a crime, or it may be someone’s actions during a crime. Example: Someone seen running away from a bank robbery holding a bag of money: - the bag of money - physical evidence - the action of running away – non physical evidence.
  38. 38. Real Evidence vs. Demonstrative Evidence Real Evidence That which is generated by criminal activity. Found at the crime scene or elsewhere and pertains to the crime. Eg: fingerprints left at the scene or those obtained from a suspect; drugs, bullets, blood etc. Demonstrative Evidence This is created to help explain or clarify real evidence. Generated after the crime by a criminal investigator or forensic scientist. Eg: (i) A 3D model of a crime scene made from photographs and measurements. (ii) A chart or graphs from an analytical instrument that shows some property of a substance.
  39. 39. Known vs. Unknown Evidence Some of the most important questions that are askedabout evidence at crime scenes are: “Do we know where this evidence came from?”, “What is its source?”, “Who left it?” Successful reconstruction of a crime scene depends upon being able to associate evidence with particular people or objects. The term unknown evidence always refers to the evidence at a crime scene whose source is unknown. Eg: A bullet found in the body of the victim of a homicide is unknown evidence. At the time the bullet is discovered to be an evidence, the bullet’s source is unknown.
  40. 40. An example. • A burglar breaks into a house by breaking a glass window and climbing through. • On his way in, he cuts himself on the broken glass that is still in the window, and leaves some blood on the glass. •Some of the broken glass from the window falls to the ground, where the burglar steps on it and gets some embedded in his shoe. •After the crime is committed, the investigators examine the scene and find the blood on the glass in the window. • The blood on the glass in the window – Unknown! • The (broken) glass in the window – Known. • The glass on the floor around the window – Unknown. ( It’d be tempting to say it must have come from that window; but there’s no proof. It could have been there before the crime was committed.) • Suspect is arrested – a search warrant to search his house obtained – examine shoes. • Glass embedded in his shoes – Unknown! could have come from anywhere. •Compare glass in his shoes with glass in the window (known).
  41. 41. Evidence Eg: Fingerprint examiners often testify in court that a latent fingerprint found on an object definitely came from a particular finger of the suspect. There are characteristics of each fingerprint on each person that make that print unique. All fingerprints are measurably, demonstrably unique! In most cases, the number of possible sources is unknown. Eg: Fiber experts testifying in court that blue denim fibers found at murder scene could have come from the pants worn by the suspect. Fibers in a given pair of pants are not unique! Mass production. Concept of individuality and uniqueness! Individual Evidence : Evidence that could have arisen from only one source. Class Evidence: Evidence that could have any number of sources.
  42. 42. Individual Evidence Evidence Type  Fingerprints (also palm prints and footprints) Comparison of minutiae with known.  Handwriting Comparison with known handwriting  Bullets and casing Comparisons with markings or knowns  Shoe prints and tire treads Comparison details with known  Large pieces of paint, glass or paper Fracture match or tear match comparison with known. Individualising Test
  43. 43. Class Evidence Evidence Type Why Not Individual? Tiny glass or paint fragment Too small to fracture-match; no unique characteristics Soils Too much horizontally and vertically Hairs and Fibres Can be individualised if DNA-Typed, else there are no unique structural characteristics in hairs and fibers. Illicit drugs Can identify drug, but cannot prove that one specimen of drug came from a particular source. Fire residues Can identify class of residue (eg: gasoline), but cannot prove that *that* gasoline came from one particular can or pump.
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The PowerPoint file used in class on 25, 28 and 29 November, 2016.


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