First Test Study Guide
First Test Study Guide FRSC 367
Popular in Forensic Chemistry
Popular in Criminology and Criminal Justice
This 7 page Study Guide was uploaded by Kayli Antos on Saturday September 19, 2015. The Study Guide belongs to FRSC 367 at Towson University taught by Mark Profili in Summer 2015. Since its upload, it has received 93 views. For similar materials see Forensic Chemistry in Criminology and Criminal Justice at Towson University.
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Date Created: 09/19/15
Forensic Chem Test 1 12 Solvability Factors 000000000 0 0 Having a witness Knowing the suspects name Knowing the suspects location Having the suspects description lDing the suspect Having property with identifiable or traceable markingsnumbers lDing an M0 Having an vehicle description Believing that publicizing or further investigation will help solve a crime Being able to narrow down suspects to a single individual who committed the crime Having significant physical evidence to impress a jury Having positive results from crime scene evidence Physical Evidence 0 Advantages quot1erkwsical object that can help a jury better visualize the crime quot llmadefense cannot distort physical evidence that is present in the court room it Witnesses can forget specific details or be intimidated into not testifying An object cannot quot1Ekmmacases need physical evidence to link a suspect to a crimescene quotillmadefense can have their own experts test the evidence CYassYha vjdba Characteristics i Hass characteristics are general can only eliminate a suspect not identify one and are shared by all members of a class it lndividual characteristics are more specific can include wear patterns and accidental markings can help to set an object apart and can help implicate a suspect Comparison Standardsantrols quotIt Types of standards gtgt Comparison Standard Collected from known source like suspect s apartment and used to compare to unknown like from a crime scene to see if they both have the same source II it gtgt Reference Standard Collected from a verified source and used to test identity and composition of unknown like suspected heroin from a crime scene being compared to known heroin supplied from a source such as NlDA or ASTM gtgt Exemplar Comparison standard for documents Must have both class and individual characteristics Types of controls gtgt Background Controls Sample of the surface the evidence was on or the medium the evidence was in the evidence is responsible for possible positive testing results gtgt Positive Controls Will produce a positive test result gtgt Negative Controls Will produce a negative test result 0 Common Yypes of fhysjca Edeence FFPFFPFFFPFPPPPFFFPFFF 739 CD UQ 33 1 blood semen saliva documents drugs explosives fibers fingerprints firearmsammunition glass hair impressions paint petroleum products plastic bags plasticrubber powder serial numbers soilminerals tool marks vehicle lights woodvegetation Requirements of Evidence Collection Tested to ensure that only Must have a search warrant if one is required If not any evidence collected is not admissible in court fruit of the poisonous tree The scene must be documented as found using notes photographs sketches and sometimes video or virtual reconstruction All physical evidence must be bagged if possible and labeled with the case number date and time of collection and signature and ID number of the collector Chain of custody must be maintained until trial otherwise evidence is not admissible in court The Role of the Criminalist 0 Provide investigative leads through scientific examination of evidence and crime scene reconstruction 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 constantly educate themselves on the everchanging and eXpanding field of forensic science Law and Science O Forensic analysts must have no bias and work independently of the political system even though most work under police jurisdiction and administration Must have ethical work practices Must understand that courts will resolve issues related to forensic science by themselves without consulting a forensic scientist FryeDaubert O O The Frye standard of physical evidence is that the court must decide if the technique procedure or principle is generally accepted in the scientific community Can present eXperts books and papers to back up science The Daubert standard is that judge is the gatekeeper and is able to decide for themselves what general acceptance is too much the evidence they want to admit based on if the techniquetheory has been tested if it s been subject to peer review the rat of error and the maintenance of standards controlling the operation In the Kumho Tire case it was decided that the judges gatekeeping role can extend beyond scientific testimony to all eXpert testimony Quality Control O O O O Unknowns are run against knowns and standards There are positive negative blank and blind controls Use calibration curves To quantify an unknown run spikes which are internal standards Quality Assurance 0 Rules are procedure SOP implemented to ensure the quality of work done in the lab Ensures that all outside and internal regulations and requirements are met The ASTM American Society for Testing and Materials provides external standards and QA and sets standards for forensic tests NIST the National Institute of Standards and Technology create update and distribute SRMs standard reference materials to forensic labs Helps ensure that all results can be traced back to one source and are therefore easily defendable NlST also provides certified weights to help with calibration programs may have staff education requirements peer review of results auditing of testimony eeeeg requirements for case file documentation distribution of reports evidence handling and laboratory security ltrnx ciency tests to determine the error rate of criminalists n Forensic Microscopy O O M croanalysjs quotitlhnst inucroscopes and microscopic techniques in order to observe and analyze microscopic evidence Fbrensjc M croscopes i Euereoscopic dissecting low magnification good for dissection of small organisms gtgt most frequently used for forensic applications gtgt use reflected light gtgt 3D imagine projected right side up and correctly left to right gtgt magnification 2X to 125x quot1kmmmmnd magnifies at higher levels than the stereoscopic gtgt transmitted light 11 9 9 9 virtual image upside down and backwards multiple lenses with varying intensities monocular o binocular VVVV up to lOOOX magnification Comparison two microscopes connected through the eyepiece good for comparing evidence to see if it originated from the same source Polarizing uses polarized light to measure optical properties Microspectrophotometer measures absorbance Scanning Electron most commonly used for biological analysis 0 Yermjnology39of a M eroscope E if it it 1 Magnification amount an object gets enlarged by lens system Working Distance distance between subject and objective lens Depth of Field height above and below point of focus where object appears focused Angle of Acceptance maXimum angle that light can hit and still reflect back into the lens Numerical Aperture ability of objective lens to separate images so they appear defined Resolving Power Resolution ability to distinguish individual objects from each other Kohler lllumination using transmitted and reflected light to evenly illuminate specimen UVVis Spectrophotometry o Spectrophotometer 9 it it Spectrophotometer measures intensity of light after it passes through a sample I and compares it to intensity of light beforehand IQ expressed as a percent This ratio is called transmittance and is often Absorbance is based on transmittance and can be determined by taking the negative log of the percent Can also measure reflection by calculating ratio of intensity of light reflected off sample to intensity of light reflected from a reference Also expressed as a percent Basic parts are light source sample holder diffraction grating and detector Can use single or double beams of light 0 M crospectrophotometry ieI Fwds microscope integrated with a UVvis spectrophotometer Only exist as single beam quotlefimmacan measure reflection and transmission Forensic Analytical Scheme o Streaming of EVjabnce color tests solvents microscopic examinations microcrystalline tests UVVis 0 Separation Zechnjques it TLC 9 CC quotIt HPLC it electrophoresis i i i i o abntjficatjon Zechnjques it MS 9 TR Different Kinds Of Chromatography 0 Liquid EPIC column 7Z6 l f stationary phase like silica or alumina hampudc solvent as mobile phase o 66 quot1Ehxnionary phase with high boiling point above 300 C in a film on inside of column Usually polymer or wax elh le phase is an inert carrier gas like helium TLC 0 Plate covered in thin layer of silica stationary phase 0 The mixture is spotted towards the bottom of the plate Known standards should be run with it and they must all be level with each other 0 The plate is then placed into the mobile phase the solvent The solvent must not come up above the spots when the plate is initially placed into it 0 Plate must be removed before solvent front reaches the top 0 Use UV light to visualize colorless spots 0 Quantify results by calculating Rf value Column Chromatography Packed With polar stationary phase Nonpolar solvent run through With analyte Get the best separation by running the column multiple times with solvents of increasing polarities n Reserve Phase Chromatography 0 Non polar stationary phase and polar mobile phase 0 Mainly used in HPLC
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