FORS311: Forensic Chemistry and Toxicology PDF

FORS311: Forensic Chemistry and Toxicology Forensic science applies science principles, techniques, and methods to the investigation of crime. At first, this definition of forensic may seem to have no connection with the more popular crime-solvi...

FORS311: Forensic Chemistry and Toxicology Forensic science applies science principles, techniques, and methods to the investigation of crime. At first, this definition of forensic may seem to have no connection with the more popular crime-solving description— but it does. The legal truth is sought through the use of the adversarial system (rather than the scientific method), and decisions are made only after each side has been given an equal opportunity to argue all the issues at hand. To analyze physical evidence, forensic chemistry draws on chemistry principles and concepts. Investigating the physical and chemical properties of a substance is central to forensic chemistry. Without an appreciation for these properties and the scientific method, forensic chemistry would not be possible. Basic Concept of Forensic Chemistry Questioned sample - the sample being analyzed having an unknown identity Known sample - the sample having a known identity and origin Evidence – available body of facts or information indicating whether the belief or proposition is true or valid. Scientific method – the principles and procedures for the systematic pursuit of knowledge.  FORS311: Forensic Chemistry and Toxicology Theories of Forensic Chemistry The chemist follows a specific process, based on the scientific method, for analyzing evidence. Samples collected from a crime scene and brought to the lab for analysis are called questioned samples because the identities and origins of those samples are unknown. In order to draw conclusions about the identity or origins of questioned samples, the forensic chemist will need known samples as a reference. A known sample might be collected as part of the evidence—for instance a hair sample collected from a suspect Forensic analyses may perform to (1) identify a questioned sample or (2) compare a questioned sample to a known sample for the purpose of determining the source or origin of the sample (where it came from). ROLES OF FORENSIC CHEMIST Most forensic scientists analyze evidence in a crime laboratory and spend little time at the crime scene. The duties of forensic scientists are not exactly as they are portrayed on many popular television shows, where the crime scene investigator plays the role of Sherlock Holmes and does everything from collecting the evidence to solving the crime. In real life a team of experts does the job of television’s crime scene investigators. The forensic scientists do not directly solve crimes; they simply analyze the physical evidence. Forensic chemists analyze non-biological trace evidence found at crime scenes in order to identify unknown materials and match samples to known substances. They also analyze drugs/controlled substances taken from scenes and people in order to identify and sometimes quantify these materials. They must follow strict procedures regarding the handling and documentation of evidence, as well as scientific protocols to ensure the quality and reliability of tests and equipment.  FORS311: Forensic Chemistry and Toxicology The pressure from law enforcement personnel to speed results can be intense, so the forensic chemist must be able to prioritize well and work efficiently while ensuring that the results are accurate. Testifying in court requires strong communication skills, including the ability to remain calm in the face of cross-examination and explain complex scientific procedures in a manner juries can understand. RULES IN THE PRACTICE OF FORENSIC CHEMISTRY The six golden rules in the practice of forensic chemistry are; 1. Go slowly - good work cannot be hurried, therefore take all the time necessary to make the case complete, no matter how urgent it may appear or how pressing others may be for the result; it is generally possible to adjourn a case if the work cannot be finished in time. 2. Be thorough - Make a careful and minute examination of everything and do not be satisfied with a qualitative analysis if a quantitative one be possible; it always pays to do too much rather than too little and it is difficult to foresee what will or will not be required in Court. 3. Take notes - Keep a full, neat and clear record of everything seen and done. 4. Consult others - Many cases will lead the expert into paths with which he is not familiar, and when this happens, he should consult those who are most likely to know. 5. Use imagination - This is somewhat hazardous advice, since an expert with a vivid and uncontrolled imagination is a most dangerous person; a disciplined imagination, however, which enables inferences and deductions (to be verified or discarded at a later stage) to be made from slender and incomplete premises is often very useful. In writing the report, the imagination must be kept well in hand. The expert should remember that what to him maybe merely a helpful working hypothesis is liable to be taken by others for more than its actual worth and adopted by them as a final explanation. 6. Avoid complicated theories - The simplest explanation is the most likely to be the right one.