Introduction to Forensic Chemistry PDF

INTRODUCTION TO FORENSIC CHEMITRY  1858: First medical textbook printed HISTORY OF – Manual de Medicina Domestica by Dr. Rafel Genard FORENSIC 1871: Teaching of legal medicine CHEMISTRY in 1876: Creation of the position Medico Titulares the Philippines –...

INTRODUCTION TO FORENSIC CHEMITRY  1858: First medical textbook printed HISTORY OF – Manual de Medicina Domestica by Dr. Rafel Genard FORENSIC 1871: Teaching of legal medicine CHEMISTRY in 1876: Creation of the position Medico Titulares the Philippines – Role: medico legal aid in administration of justice 1884: Anacleto del Rosario as chemist in the committee to study mineral waters of Luzon 1887: Laboratorio Municipal de Manila was created – Functions: analysis of food and water – Materials standpoint of Public Health and Legal Medicine 1894: rules regulating the services of “Medico Titulares y Forences”  1895: Antonio Luna established a clinical laboratory of HISTORY OF Chemical Analysis. FORENSIC 1898: Preservation of the Spanish Forensic Medicine CHEMISTRY in System by the American Civil Government the Philippines 1899: Establishment of the first crime laboratory by the US army First Scientific Laboratory on the Banks of Pasig River 1901: A. Bureau of Government Laboratories (BGL) was created (Act No. 156, Civil Commission) B. Provincial Insular and Municipal Board of Health to perform Medico-Legal Duties of the “Medico Titulares”  1908: Teaching Legal Medicine and Ethics in Philippine HISTORY OF mEdical Schools (UP) FORENSIC 1915: Creation of Legal Medicine with authority to collect CHEMISTRY in materials in the interest of Medico-Legal Questions. the Philippines 1922: Department of Lwegal Medicine of UP became a branch of the Department of Justice 1937: Creation of Division of Investigation (DI) under DOJ with Medico-Legal as part of the Division 1938: Department of Legal Medicine abolished and later on turned-over to the Medico-Legal Section of DI 1939: PC having its own medico-Legal office with chemical laboratory 1942: Creation of NBI  1945: PC Crime Laboratory activated the Fingerprint Identification Unit Forensic Chemistry added to Fingerprints HISTORY OF Unit. FORENSIC 1947: Criminal Laboratory Branch of PC (Ballistics, CHEMISTRY in photography, and Fingerprint) the Philippines 1951: New sections added: – Mobile Unit – Lie Detection Section – Physical Identification Section 1959: Independent Technical Laboratory Branch (PC Forensic Laboratory) – PC Laboratory became PNP crime laboratory – Present: Two distinct Crime Laboratory in the Philippines ◦ Forensic Chemistry Division of NBI ◦ PNP Crime Laboratory  Collection of physical evidence Forensic Chemistry –Application of chemical principles, techniques, and Analysis of physical evidence methods in the examination of physical evidence Interpretation of all evidence Presentation of evidence in court Crime Lab Units Standard Optional Physical Science (Chemistry, Toxicology Physics, Geology) Fingerprints Biology Polygraph Firearms Voice Print Documents Photography NBI Crime Laboratory Role of a Forensic Chemist 1. Collection or Reception of the Specimen to be examined a. Sufficiency of the specimen b. Obtaining Standard for comparison c. Maintenance for individuality/Identification d. Labeling and Sealing 2. Actual Examination of Specimen a. Scrutinize, document complete description of external appearance and manner of collection b. Take photographs if possible c. Weigh, measure, record 3. Communication of Results – a written report is made by the chemist 4. Court Appearance – oral evidence is done if the case is brought to court Evidence – is the means, sanctioned by these rules (law), of ascertaining in judicial proceedings the truth respecting a matter of fact [Rule 128, Sec. 1, Rules of Court] ◦ Means – way to provide something in court ◦ Sanctioned by the rules – admissible in court ◦ ascertaining in judicial proceedings the truth respecting a matter of fact – you can present the means to prove something or the truth. ◦ Have undergone several tests and the result is accurate. Classification of Types of Evidence Direct evidence – that (if true) proves an alleged fact, such as an eyewitness account of a crime Circumstantial evidence – (indirect evidence) evidence used to imply a fact but not prove it directly Physical evidence refers to any material items that would be present at the crime scene, on the victims, or found in a suspect’s possession. – Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells. Types of Physical Evidence Transient evidence is temporary; easily changed or lost; usually observed by the first officer at the scene. Pattern evidence is produced by direct contact between a person and an object or between two objects. Conditional evidence is produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances or sequence within a particular event. Transfer evidence is produced by contact between person(s) and object(s), or between person(s) and person(s). Associative evidence is something that may associate a victim or suspect with a scene or with each other; e.g., personal belongings.  Class vs Individual Characteristics CLASS CHARACTERISTICS INDIVIDUAL CHARACTERISTICS Properties of evidence that can be Properties of evidence that can associated with a common source with only be associated with a group an extremely high degree of certainty and never with a single source Examples Examples fingerprints One-layer paint chip on cars striation markings on bullets or tools ABO Blood type irregular and random wear patterns in tire or footwear impressions handwriting characteristics What will evidence collected at a scene do for the investigation? May prove that a crime has been committed Establish key elements of a crime Link a suspect with a crime scene or a victim Establish the identity of a victim or suspect Corroborate verbal witness testimony Exonerate the innocent. Give detectives leads to work within the case Source: http://www.virtualsciencefair.org/2004/fren4j0/public_html/trace_evidence.htm Why is Physical Evidence Important? The examination of physical evidence by a forensic chemist is usually done for identification or comparison What is the Purpose of Identification of Physical Evidence? Identification is the determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. Example: Chemical composition of drugs Identification of gasoline in residues recovered from the debris of a fire Identification of blood, semen, hair, wood would also include a determination of origin (did the bloodstain originate from a human, dog, cat…?) Why is Comparison of Physical Evidence Important? A comparison analysis subjects a suspect specimen and a standard/reference specimen (victim/evidence found at the crime scene) to the same tests and examinations for the ultimate purpose of determining whether they have a common origin. – Ex: a paint chip found on a hit-and-run victim’s garment may have to be compared with paint removed from a suspect vehicle – Ex: hair found at a crime scene may be compared to the hairs removed from a suspect’s head General Rules in the Collection of Evidence a. Obtain it legally b. Note details and description of collected evidence c. Proper identification of evidence d. Proper packaging, sealing and storage e. Proper shipping/delivery to the laboratory as soon as possible f. Maintaining Chain of Custody Factors Contributing to the Loss of Physical Evidence a. Lack of precautions preventing tampering of specimen b. Failure in the preservation c. Failure in the transport of specimen d. Failure in identifying the specimen e. Improper packaging of the specimen Scientific Method – the process of investigation involving observation and hypothesis testing Evidence Samples Questioned Samples –The unknown, usually collected at the crime scene Control Samples – used for comparison with Questioned samples, details are known Questioned samples are identified through tests of physical and chemical properties Physical Properties and Changes Physical properties are properties that can be measured without changing the identity of the evidence ex) density, color, melting point, Physical Changes occur and do not alter the chemical makeup of the substance Chemical Properties and Changes Chemical properties determine how a substance behaves in the presence of other substances Chemical changes once they occur, there is no going back. Presumptive & Confirmatory Tests Presumptive tests allow a field investigator to screen evidence to reduce the number of possibilities and to get a preliminary identification. Confirmatory tests are used to make a more specific identification. Analytical Techniques Quantitative Analysis – results are measureable amount or quantity Qualitative Analysis – description using words Principles Used in Forensic Chemistry 1. Law of Individuality – every object, natural or man-made, has an individuality which is not duplicated in any other object. 2. Law of Progressive Change – everything changes with the passage of time. 3. Principle of Comparison – only “likes” (similarities) can be compared 4. Principle of Analysis – the analysis can be no better than the sample analyzed 5. Law of Probability – all identifications, definite or indefinite, are made consciously or unconsciously on the basis of probability