"Unlocking The Power of Forensic Science
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Forensic science applies scientific methods to support legal decision-making in criminal and civil law, focusing on areas such as forensic chemistry and document examination. It categorizes evidence into impressions (latent, patent, and plastic) and analyzes questioned documents to establish authenticity and detect alterations. Additionally, bloodstain pattern analysis interprets bloodstains to reconstruct events surrounding a crime, utilizing biology, physics, and mathematics to answer critical investigative questions.
"Unlocking The Power of Forensic Science
- 1. Forensic science Hari Prasad P M
- 2. Forensic science, also known as criminalistics, is the application of scientific principles and methods to support legal decision-making in matters of criminal and civil law. During criminal investigation in particular, it is governed by the legal standards of admissible evidence and criminal procedure. Assignment 1: Origin and need of forensic science
- 3. Forensic chemistry is the application of chemistry and chemical methods, using modern analytical equipment, to assist in the identification of unknown materials found at a crime scene.
- 4. Trace or Contact evidences
- 5. Marks and Impressions Impression evidence is created when two objects come in contact with enough force to cause an impression or a mark. These are for two type Two dimensional : A fingerprint Three Dimensional : The marks on a bullet caused by the barrel of a firearm. Categories of prints There are three basic categories or types of impressions that may be deposited, detected, developed if need be and recovered at a crime scene. 1. Latent 2. Patent 3. Plastic or Molded
- 6. 1. Latent The skin has deposits of oil and perspiration that normally coat the surface. When the hand touches the surface, some of the moisture is transferred from the hand to the object, leaving an impression of the friction ridge detail. These are referred to as latent impressions. On most surfaces the latent impressions are not readily visible. The word latent is defined as not visible. That does not mean that it is actually invisible. Using available or oblique lighting on most surfaces will reveal the impression. The impression must be enhanced or developed to be seen fully and collected. 2. Patent A patent impression occurs as the result of transferring a foreign material coating the skin of the fingers. Examples of the foreign material would be substances like paint, tar, grease, blood, or ink. The best example of a patent impression would be the ink standards or elimination's that we as investigators collect from individuals. After the ink is applied it becomes the foreign material coating the hands of the individual. A card is used as a transfer medium, thus becoming the object touched and a transferring of the patent impression takes place. The word patent means obvious or evident. Patent impressions are visible and usually need no enhancement. They are simply photographed and the item that they are deposited on is collected if necessary. The photograph and or object actually becomes the investigators lift. 3. Plastic or Molded A plastic or molded impression is deposited when the hands, fingers, or feet is pressed into a soft rubbery type material that will retain the impression of the ridge detail. Where a latent impression is deposited on the surface, a plastic or molded impression would be deposited into the surface. Examples of the materials where a plastic impression would be deposited are clay, wet paint , blood, or tar. Plastic or molded impressions are visible and usually need no enhancement. They are simply photographed and if necessary the item is collected and may have the ability to be caste.
- 7. Forensic Document Examination In forensic science, questioned document examination (QDE) is the examination of documents potentially disputed in a court of law. Its primary purpose is to provide evidence about a suspicious or questionable document using scientific processes and methods. Evidence might include alterations, the chain of possession, damage to the document, forgery, origin, authenticity, or other questions that come up when a document is challenged in court. Examination types Examinations and comparisons conducted by document examiners can be diverse and may involve any of the following: Handwriting (cursive / printing) and signatures Typewriters photocopiers, laser printers, ink-jet printers, fax machines Chequewriters, rubber stamps, price markers, label makers Printing processes Ink, pencil and paper Alterations, additions, erasures, obliterations Indentation detection and/or decipherment Sequence determination Physical matching
- 8. Handwriting examinations Handwriting recognition The examination of handwriting to assess potential authorship proceeds from the above principle of identification by applying it to a comparison of samples of handwritten material. Generally known as ACE-V, there are three stages in the process of examination. Analysis or Discriminating Element Determination: The unknown item and the known items must, by analysis, examination, or study, be reduced to a matter of their discriminating elements. These are the habits of behavior or of performance (i.e., features or characteristics and, in other disciplines, the properties) that serve to differentiate between products or people which may be directly observable, measurable, or otherwise perceptible aspects of the item. Comparison: The discriminating elements of the unknown, observed or determined through analysis, examination, or study, must be compared with those known, observed, or recorded of the standard item(s). Evaluation: Similarities or dissimilarities in discriminating elements will each have a certain value for discrimination purposes, determined by their cause, independence, or likelihood of occurrence. The weight or significance of the similarity or difference of each element must then be considered and the explanation(s) for them proposed. Optionally, the procedure may involve a fourth step consisting of verification/validation or peer review.
- 9. Bloodstain pattern analysis is performed in two phase 1. Pattern Analysis looks at the physical characteristics of the stain patterns including size, shape, distribution, overall appearance, location and surface texture where the stains are found. 2. Reconstruction uses the analysis data to put contextual explanations to the stain patterns Bloodstain pattern analysis (BPA) is the interpretation of bloodstains at a crime scene in order to recreate the actions that caused the bloodshed. Analysts examine the size, shape, distribution and location of the bloodstains to form opinions about what did or did not happen. BPA uses principles of biology (behavior of blood), physics (cohesion, capillary action and velocity) and mathematics (geometry, distance, and angle) to assist investigators in answering questions such as: Where did the blood come from? What caused the wounds? From what direction was the victim wounded? How were the victim(s) and perpetrator(s) positioned? What movements were made after the bloodshed? How many potential perpetrators were present? Does the bloodstain evidence support or refute witness statements?
- 10. How Bloodstain Evidence is Collected Bloodstain samples can be collected for BPA by 1. Cutting away stained surfaces or materials 2. Photographing the stains 3. Drying and packaging stained objects. The tools for collecting bloodstain evidence usually include high-quality cameras (still and video), sketching materials, cutting instruments and evidence packaging. Bloodstain Pattern Analysis- steps Collection of Blood strains Documentation of Bloodstain Evidence DNA Profiling Assignment 2: Sampling Bloodstains For DNA Profiling