Forensic Chemistry & Toxicology PDF

MODULE FORENSIC CHEMISTRY AND TOXICOLOGY CHAPTER 2: RCP (RECOGNITION, COLLECTION & PRESERVATION) OF PHYSICAL EVIDENCE Objectives: a) Apply knowledge of correct handling and p...

MODULE FORENSIC CHEMISTRY AND TOXICOLOGY CHAPTER 2: RCP (RECOGNITION, COLLECTION & PRESERVATION) OF PHYSICAL EVIDENCE Objectives: a) Apply knowledge of correct handling and processing of physical evidence b) Develop skills in preservation and transportation of physical evidence WHAT IS CRIME SCENE? Crime scene is an area or vicinity of occurrence of physical evidence. Crime scene processing can be done through scientific crime scene analysis – a slow, methodical, systematic, and orderly process of collecting physical evidence, based on proper recognition and collection, to be process in a laboratory by a specialist or a forensic examiner to uncover significant clues for them. Crime scene investigation is much more than processing (searching), documenting (notes, photos, and sketches), and certainly, more than bagging and tagging/ markings physical evidences, the main objective is to know how to recognize physical evidences to be processed. RECOGNITION OF PHYSICAL EVIDENCE IN A CRIME SCENE o Recognition is a qualitative process of systematically evaluating physical evidence to determine if their qualifications are sufficiently similar or substantially equivalent to established and published standard of the receiving laboratory jurisdiction or country. ❖ Identity as One Way of Recognizing Physical Evidence o Identity is always sought during criminal investigation. It is often asking whether the physical evidence found in the suspect’s possession can be linked to the crime scene. ❖ Important concepts on the quality and use of physical evidence 1|Page  MODULE FORENSIC CHEMISTRY AND TOXICOLOGY a. Mathematical probability – most of the human action requires judgements. The outcome of an event can be logically estimated based on past performance, known conditions and experience. b. Individual characteristics – what make one thing different from all other similar items are individual characteristics. c. Class characteristics – while class characteristic is a property of evidence that can only be associated with a group and never with a single source. d. Comparison – the obvious physical match between objects. Example are rip, tear, or breakage of a counterpart of for the object that was used to inflict the damage. e. Rarity – the exceptional circumstances connected with the place, time, or general conditions under physical evidence is discovered tend to heighten its quality. f. Exchange – when two objects come into contact, there is always a transfer of small materials between the two. ❖ LOCARD’S EXCHANGE PRINCIPLES in recognition of Physical Evidence o Locard’s exchange principle is a concept which states that “Whenever a criminal comes into contact with a victim, an object, or a crime scene, he or she will leave evidence, and will also take away evidence” o Edmund Locard (early 20th century) a Frenchman who sets up a forensic laboratory in Lyons, France. He is considered as the Father of Edmond Locard Forensic Science. o Sherlock Holmes – a fictitious character but considered as the Father of Crime Detection. o Dr. Hans Gross – written the first investigation book entitled “Search for the Truth” and known as the “Father of Criminalistics” Hans Gustav Adolf Gross 2|Page  MODULE FORENSIC CHEMISTRY AND TOXICOLOGY COLLECTION OF PHYSICAL EVIDENCE o Before collection, participate in any scene debriefing to determine post-scene responsibilities; to share and determine which sample needs specialist. ❖ Factors to be considered in collection of physical evidence a. Maintain the integrity of the evidence – should be intact and never remove from the material that contains them as found in the crime scene as possible. Use plastic or glass bottles, manila envelopes, screw-capped glass vials, pillbox or used the folded paper (druggist fold). b. Mark for proper identification – Markings was placed at the time of collection, and if possible, put their initial and date on the evidence itself and if not, on an evidence lag. c. Photograph before collection – Fragile evidence is collected right after being photograph and use forceps in picking small items to prevent contamination. d. Obtain control standards from known samples, that is from a known origin, for comparison purposes. e. Observe method of collection/removal – vacuums are used for fiber, dirt, glass, and hair. Plaster or dental stone are used for foot/ shoe and tire print. Other evidence has special methods of removal. Human bodies require special attention, and examiner/ searcher are only allowed to make a non-intrusive examination and do sketches. The body belongs to coroner or medical examiner. 3|Page  MODULE FORENSIC CHEMISTRY AND TOXICOLOGY PROCESSING OF PHYSICAL EVIDENCE o Many collected physical evidences are not suitable for a laboratory analysis. To perform a meaningful chemical analysis, we must be obtaining a laboratory SAMPLE. ❖ Sample is a small, homogenous (same throughout) sample whose composition is representative of the larger/ real object. ❖ Sampling is the process of selecting representative material to analyze. ❖ Goals of sampling involves two things o To obtain representative samples o To avoid any bias in the selection of this sample ❖ Classification of Sampling 1. NON-PROBABILITY SAMPLING/ JUDGEMENT OR AUTHORITIES SAMPLINGS – samples often are chosen using the expertise of those who have a feel for the process and believe that they intuitively know when and where to obtain a representative sample. This often contains hidden biases, and statistical methods for the estimation of precision cannot be applied. 2. PROBABILITY SAMPLING – ensures that the sampling scheme is developed in such a manner that will yield samples that are highly indicative of the properties in the bulk ensemble. A sample must be large enough to give a good representation of the population, but small enough to be manageable. ❖ Methods of Sample Smuggling o SMURFING – 50 grams of shabu is required by the trafficker, the pusher will effort to give this amount via courier to purchase and bring only 49 grams to avoid the maximum penalty. o SLOPPING – purchasing contaminated or diluted chemical from legal source during transfer clearing process. 4|Page  MODULE FORENSIC CHEMISTRY AND TOXICOLOGY References: Bell, Suzanne, Forensic Chemistry, Pearson Prentice Hall, Upper Saddle River, New Jersey 07458, 2006. Sunico, Lorenzo Forensic Chemistry, NBI, Manila. Saferstein, Richard, Criminalistics: An Introduction to Forensic Science, 2nd edition, Prentice Hall New York, 2001. Fox, Richard and Cunning Carl. Crime Scene Search and Physical Evidence Handbook, US Department of Justice, Law Enforcement Assistance Administration, NILECJ, 1973. LINKS TOPIC LINK FOR VIDEO Physical Evidence: Preserving the Truth https://www.youtube.com/watch?v=awcnMrZiSmU Collecting Blood Evidence, Luminol and https://www.youtube.com/watch?v=8zCaz0U94JI Blue Star 5|Page