Profili Forensic Chemistry 8/26 8/31, 9/2,
Profili Forensic Chemistry 8/26 8/31, 9/2, FRSC 367
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This 7 page Class Notes was uploaded by Kayli Antos on Sunday September 6, 2015. The Class Notes belongs to FRSC 367 at Towson University taught by Mark Profili in Summer 2015. Since its upload, it has received 83 views. For similar materials see Forensic Chemistry in Criminology and Criminal Justice at Towson University.
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Date Created: 09/06/15
Fbrensic Chem Profili Fall 2015 12 Solvability Factors Having a witness to the crime Knowing the alleged suspects name Knowing where the suspect is located Having a description of the alleged suspect Identifying the suspect Having property with identifiable or traceable markings or numbers Identifying a significant MO Having a description of the suspects automobile Being of the belief that publicizing or further investigating the crime will aid in its being solved The opportunity for being able to narrow down the precise individual who committed the crime Having significant physical evidence to impress a modern jury Having positive results from a crime scene evidence search Physical Evidence Advantages I It provides a tangible object when can be taken into the court room for the jury to see to better help visualize what happened during the crime I The defense cannot distort physical evidence when it is present in from of the court I Not subject to memory loss or intimidation like a human witness I Some cases cannot be solved without physical evidence to connect a suspect to a crime scene I The defense can have their own experts test the physical evidence and present those findings in court Class And Individual Characteristics I Class characteristics do not point to a particular suspect but they can eliminate one I Individual characteristics can further narrow down a suspect some types more than others I Class characteristics are shared by all members of a class Individual characteristics include all of the class characteristics to which said object belongs and can set the object apart from others like it The pattern of class and individual characteristics is unique to each object and is called individualization 0 comparison StandardsAnd centrols Standards must be materials from a known source They can be Acomparison standard These standards are materials collected from a known source and are used for comparison to an unknown sample in order to determine if the unknown came from the same source as the known v Areference standard These standards are collected from sources which have been verified as to their source and identity They are used to verify the composition of unknown samples v39Exemplar Comparison standard for document analysis Must contain both class and individual characteristics of the known document Controls are items that are tested alongside the questioned evidence to determine if there are any problems with the integrity of the evidence or the testing procedure There are background controls the surface the evidence was taken from or the medium it is in whatever could have contaminated the evidence positive controls and negative controls 0 Legal Requirements of Evidence CbJJection Search and seizure laws must be followed Must have a search warrant if it is needed The scene must be documented in the way it is found Using notes photographs sketches sometimes video The physical evidence collected must be bagged if possible and labeled with 39the case number 39the date and time of collection 39the signature and ID number of the collector I The chain of custody must be maintained until the trial Understanding The Role Of The Criminalist Law Through the scientific examination of the evidence collected and crime scene reconstruction they can provide investigative leads Can provide expert testimony in court Educate law enforcement officials investigators attorneys medical professionals judges and others on how best to collect present and understand physical evidence Must ask questions and know how best to investigate and examine the available evidence Must constantly educate themselves on the changing and growing field in which they work And Science Forensic scientists must have no bias and work independently of the political system using all relevant testing to determine the truth This independence must be maintained even though most work under police jurisdiction and administration Their work practices must be ethical Must be able to know which scientific practices are most reliable and which are not Must understand that the courts will often resolve issues relating to forensic science internally and without consultation Lawyers And Forensic Scientists They both have their own legal and moral obligations They must both work on determining what the truth and circumstances of a crime were Law is focused on outcomes while science focuses on justification whatwho vs howwhy The evidence of a crime and its admissibility in court play a crucial role in getting to the truth Theoretical Natural Sciences amp Practical Forensic Sciences Forensic scientists must have a knowledge of the legal system that natural scientists do not Must combine scientific skills with a vow to the public s good and and controlled chaotic Where theoretical sciences are certain pristine forensic sciences are uncertain contaminated Reliable Method Of Inquiry Reliable scientific methods must have integrity competence and a defensible technique Scientific Experts And Their Role Reach an explanation based off the data surrounding an event or question Suggest explanations or connections to pursue and test Distinguish what evidence is solid vs just coincidental Only a judge can declare who may be an expert witness Can only give expert opinions within their area of expertise Are only used in court when the facts of a case are unclear when the scientific procedures need explanation and clarification or when the judge needs assistance in reaching an educated decision based on the evidence Forensic Scientists Can never be completely certain of results but must be able to attach a certain degree of certainty to their work Quality Control Knownsstandards are run with unknowns Have positive negative and blank controls as well as blind controls Use calibration curves to check calibration Run spikes which are internal standards which are used to quantify an unknown Quality Assurance The rules and procedure implemented to ensure the quality of the work done in the lab What must be done to ensure that all regulations and requirements are met An official protocol that everyone from analyst to management must follow The American Society for Testing and Materials ASTM provides external standardization and QA It also sets many standards for forensic tests o The National Institute of Standards and Technology NTST creates updates and distributes standard reference materials SRMs to forensic labs o This helps ensure that results are defendable because resources and procedures can be linked back to one original source This is called traceability o NTST also helps with calibration by providing certified weights 0 QA programs may have staff education requirements peer review of results auditing of testimony requirements for case file documentation distribution of reports evidence handling laboratory security proficiency tests to determine the error rate of criminalists and Forensic Microscopy o Microanalysis This is the use of microscopes and microscopic techniques in order to observe and analyze evidence that could not otherwise be clearly seen 0 Forensic Microscopes Stereoscopic microscope also called a dissecting microscope for its low magnification which lends itself to dissections of small objects Compound microscope magnifies at much higher levels than the stereoscopic two microscopes connected Used for comparing fibers Comparison microscope through the eyepiece projectiles etc Polarizing microscope uses polarized light which gives less glare Used to measure optical properties Microspectrophotometer measures absorbance Electron microscope uses electrons instead of light More commonly used for biological analysis 0 Tbrminology 0fCAMicroscqpe Magnification the amount a subject gets enlarged by the lens system objective lens and ocular lens Multiplying both magnifications gives the total magnification Working Distance the distance between the subject and the objective lens Depth of Field the height above and below the point of focus where the object appears focused Angle of Acceptance the maximum angle that light can hit the object while still being reflected back into the lens Numerical Aperture the ability of the objective lens to focus separate images so they appear defined and not blurry Resolving PowerResolution the ability to distinguish individual objects from each other because of light waves passing between them Light rays must be short enough to pass between objects Kohler lllumination uses transmitted and reflected light to evenly illuminate the specimen while ensuring that the light source cannot be seen in the image 0 Light Different wavelengths of light are used for different applications Light can be reflected from above and reflects off objects surface cannot see inside specimen or transmitted light shining up through a specimen can see internally o StereoscqpicMicroscqpes They most frequently used for forensic applications Used reflected light A 3D image is projected right side up and oriented correctly right to left Typically the only way to analyze opaque evidence Usually used for soil insects and macroscopic evidence Magnification typically ranges from 2X to 125x 0 compound Microscopes Used transmitted light from a light source beneath the stage Projects a virtual image upside down and backwards Has multiple lenses with varying intensities Can be monocular or binocular I Typically up to 1000K magnification
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