1、Designation: E 1588 07e1Standard Guide forGunshot Residue Analysis by Scanning ElectronMicroscopy/ Energy Dispersive X-ray Spectrometry1This standard is issued under the fixed designation E 1588; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial corrections were made in August 2007.1. Scope1.1 This guide covers the analysis of gunsh
3、ot residue (GSR)by scanning electron microscopy/energy-dispersive X-rayspectrometry (SEM/EDS) by manual and automated methods.The analysis may be performed manually, with the operatormanipulating the microscope controls and the EDS systemsoftware, or in an automated fashion, where some amount ofthe
4、analysis is controlled by pre-set software functions.1.2 Since software and hardware formats vary among com-mercial systems, guidelines will be offered in the most generalterms possible. The software manual for each system should beconsulted for proper terminology and operation.1.3 This standard doe
5、s not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applicabil-ity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Stan
6、dard:E 876 Practice for Use of Statistics in the Evaluation ofSpectrometric Data23. Summary of Practice3.1 From the total population of particles collected, thosethat are determined by SEM to be within the limits of certainparameters (e.g., atomic number, size, or shape) characteristicof or consiste
7、nt with GSR are analyzed by EDS. Typically,particles composed of high mean atomic number elements aredetected by their SEM backscattered electron signals and anEDS spectrum is obtained from each. The EDS elementalprofile is evaluated for constituent elements that may identifythe particle as being ch
8、aracteristic of or consistent with GSR.4. Significance and Use4.1 This document will be of use to forensic laboratorypersonnel who are involved in the analysis of GSR samples bySEM/EDS.4.2 SEM/EDS analysis of GSR is a non-destructive methodthat provides3,4both morphological information and the el-em
9、ental profiles of individual particles. This contrasts withbulk sample methods, such as atomic absorption spectropho-tometry, neutron activation analysis, inductively coupledplasma atomic emission spectrometry, and inductively coupledplasma mass spectrometry, where the sampled material isdissolved o
10、r extracted prior to the determination of totalelement concentrations, thereby sacrificing morphological in-formation and individual particle identification. In addition,x-ray fluorescence spectrometry (XRF) is a bulk analysistechnique that has been used for the elemental analysis of GSR.Unlike the
11、solution-based bulk methods of analysis, XRF isnondestructive; however, XRF still does not provide morpho-logical information and is incapable of individual GSR particleidentification.5. Sample Preparation5.1 Once the evidence seal is broken, care should be takenso that no object touches the surface
12、 of the adhesive SEM/EDSsample collection stub and that the stub is not left uncoveredany longer than is reasonable for transfer, mounting, orlabeling.5.2 Label the sample collection stub in such a manner that itis distinguishable from other sample collection stubs withoutcompromising the sample; th
13、at is, label the bottom or side ofthe stub.5.3 If a non-conductive adhesive was used in the samplecollection stub, the sample will need to be coated to increase its1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01
14、on Criminalistics.Current edition approved Feb. 15, 2007. Published April 2007. Originallyapproved in 1994. Last previous version approved in 2001 as E 1588 95(2001).2Withdrawn.3Krishnan, S. S., “Detection of Gunshot Residue: Present Status,” ForensicScience Handbook, Volume I, Prentice Hall, Inc.,
15、Englewood Cliffs, NJ, 1982.4Wolten, G. M., Nesbitt, R. S., Calloway, A. R., Loper, G. L., and Jones, P. F.,“Final Report on Particle Analysis for Gunshot Residue Detection,” Report ATR-77(7915)-3, Aerospace Corporation, Segundo, CA, 1977.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C
16、700, West Conshohocken, PA 19428-2959, United States.electrical conductivity, unless an environmental SEM or lowpressure/low vacuum - SEM is used for the analysis. Carbon isa common choice of coating material, since it will not bedetected with a beryllium window EDS detector and, thus, willnot inter
17、fere with X-ray lines of interest. Furthermore, withEDS systems capable of detecting carbon, it is still ignored dueto the high signal intensity from the carbon in the adhesive. Forhigh vacuum SEM, a carbon film thickness of between 5 and50 nm is typical, with less conductive samples requiring athic
18、ker coat.6. Sample Area6.1 Sample collection stubs for SEMs typically come in oneof two diameters: 12.7 mm (0.5 in.) or 25.4 mm (1 in.), whichyield surface areas of 126.7 mm2and 506.7 mm2respectively.Analysis of the total surface area of the stub manually isprohibitively time-consuming. Because the
19、particles are col-lected onto an adhesive surface in a random manner and theparticles do not tend to cluster, it is reasonable to analyze aportion of the stub surface by employing an appropriatesampling and analytical protocol.4,56.2 When an automated SEM/EDS system is employed,data collection from
20、the entire surface area of the samplecollection stub is recommended if possible. Due to the dispar-ity between the shape of the sample collection stub (round) andthe SEM field of view search area (square or rectangular),analysis of 100% of the sample collection area may not bepossible in some system
21、s.7. Instrument Requirements and Operation7.1 General:7.1.1 Most commercial-grade SEM/EDS systems should beadequate for GSR analysis.7.1.2 Automated data collection of GSR involves someportion of the data collection being controlled by pre-setsoftware functions. The extent to which the SEM and EDSsy
22、stems communicate and are integrated varies according tothe manufacturers involved and the capabilities of thehardware/software architecture.7.1.3 A protocol should be established to confirm optimaloperating parameters on a routine basis.7.1.3.1 The EDS energy calibration and beam current sta-bility
23、 should be monitored regularly.7.1.4 If a reference sample with a known amount ofparticles (preferably GSR particles) is available, this sample(positive control) should be analyzed in regular intervals inorder to test the accuracy of particle detection, whether byautomated or manual analysis6.7.1.5
24、A stub that has not been used for collection (negativecontrol) should also be included with each sample set analyzed.7.2 Scanning Electron Microscope (SEM):7.2.1 The SEM, operating in the backscattered electronimaging mode, must be capable of detecting particles down toat least 0.5 m in diameter.7.2
25、.2 The SEM must be capable of an accelerating voltageof 20 kV.7.2.3 Automated systems will also include:7.2.3.1 a motorized stage7.2.3.2 automated stage control with the ability to recallstage locations of particles for verification7.2.3.3 particle recognition software7.3 Energy Dispersive Spectrome
26、try (EDS):7.3.1 Detector:7.3.1.1 The detector window may be constructed either ofberyllium or organic “thin” film7.7.3.1.2 The detectors resolution should be better (less) than150 eV, measured as the full width at half the maximum heightof the Mn Ka peak.7.3.1.3 The detector must be capable of resol
27、ving clearly theBa La1,Lb1, and Lb2peaks.7.3.2 Display:7.3.2.1 A calibrated, scaled display of X-ray energy versuscounts.7.3.2.2 The ability to identify and label X-ray lines and afacility for hard copy output of the display contents.7.3.2.3 At a minimum, the display should be set to 1024channels at
28、 20 eV per channel. If the software allows, the EDSdisplay should be set to 2048 channels at 10 eV per channel asthis permits better visualization (resolution) of the X-ray lines.7.3.2.4 Display of the EDS output must encompass thex-ray lines of analytical utility, with a minimum range of 0-15keV.7.
29、3.3 Automated systems will also include:7.3.3.1 software capable of acquiring for a specified collec-tion time or total counts and storing EDS spectra from multiplepoints on the sample collection stub.7.4 Sample Placement:7.4.1 For identification purposes, each sample collectionstub should contain a
30、 permanent or indelibly labeled identifierwhich can be used to reference the stub location on themicroscope stage.7.4.2 If it is anticipated or required that additional analysesor particle relocation will occur after a stub has been analyzedand removed from the microscope stage, a system should bede
31、vised so the stub can be replaced in the same orientation asbefore its removal. This may consist of marking the side ofeach stub and aligning it with marks on the microscope stageor by having stubs that fit into the stage in only one position(for example, stubs with a pin that is a half-circle in cr
32、oss-section).7.5 Detection and Calibration:7.5.1 Particles of GSR are detected by their backscatteredelectron signal intensity. The absolute signal intensity that aparticle produces is related to the electron beam current, mean5Halberstam, R. C., “A Simplified Probability Equation for Gunshot Primer
33、Residue (GSR) Detection,” Journal of Forensic Sciences, V36, N3, pp. 894897,1991.6A reference sample should have been prepared and mounted in a mannercomparable to the collection method in use by the submitting agency. Preferably, thecalibration sample will be a sample of GSR from a known source (ca
34、liber ofweapon, ammunition manufacturer, number of rounds fired, collected area fromshooter or a synthetic GSR standard. Additional environmental particles may beadded to ensure the inclusion or exclusion of particular classes of particles.7A beryllium window absorbs X-ray energies below about 1.0 k
35、eV; therefore,elements below sodium (atomic number 11) are not detected; other windowmaterials may be employed (single window light element detectors).E158807e12atomic number, and size of the particle (for particle sizes on theorder of the beam diameter). Particles whose mean atomicnumbers are high
36、will appear brighter than those of lower meanatomic number composition.As the beam current increases, theamount of signal each particle produces also increases8.7.5.2 The brightness and contrast settings of the backscat-tered electron detector system determine the limits of detectionand discriminati
37、on of particles whose mean atomic numberexceed the minimum setting but fall below the maximumsetting. Controls for the backscattered electron signal should beset on a suitable reference sample of known origin or a pureelement standard at the same parameters that will be used forthe questioned sample
38、 analysis. This calibration sample should,if possible, be in the microscope chamber at the same time asthe questioned samples to be analyzed.7.5.3 The backscattered electron detectors brightness andcontrast should be set to include those high atomic numberparticles of interest and exclude low atomic
39、 number particlesthat are not of interest. Typically, high contrast and lowbrightness settings provide an adequate range between thresh-olds for ease of detection. If the beam current is changed ordrifts, the brightness and contrast, which were based on theprevious beam current, may no longer be com
40、patible with thenew conditions and should be readjusted. The beam currentmay be measured with a Faraday cup, a specimen currentmeter, or monitored by comparing the integrated counts withinthe same peak in sequentially collected spectra from a knownstandard.8. Data Analysis8.1 Definition and Classifi
41、cation8.1.1 Morphologically, GSR particles detected and analyzedusing this method are typically spheroidal, noncrystalline(nonsymmetrical) particles between 0.5 m and 5.0 m indiameter; the remainder are irregular in shape and/or vary from1 to 100+ m in size3. It is not consistent with the mechanisms
42、of GSR formation to find particles with crystalline morphol-ogy. Particles having such morphologies would not be classi-fied as GSR regardless of their composition. Since morphologycan vary greatly, it should never be considered as the onlycriterion for identification of GSR.8.1.2 The most definitiv
43、e method to determine if a particleis characteristic of or consistent with GSR is by its elementalprofile. An approach to the identification of particles charac-teristic of or consistent with GSR is to compare the elementalprofile of the recovered particulate with that collected fromcase-specific kn
44、own source items, such as the recoveredweapon, cartridge cases or victim-related items whenevernecessary. GSR particles with non-routine elemental profilesincluding the presence of additional elements (not listed in8.1.3, 8.1.4, and 8.1.5) may be encountered in case work. Suchparticles can be consid
45、ered characteristic of or consistent withGSR (as defined in 8.1.3, 8.1.4, and 8.1.5) provided that thepresence of these additional elements can be accounted for bycase-specific sources, such as by the analysis of cartridges orammunition/weapon test fire deposits. The relative quantity ofthese other
46、elements and their distribution in the GSR particlepopulation should be consistent between the questioned andknown source samples.8.1.3 Particles with a composition characteristic of GSRwill have the following elemental profile:8.1.3.1 Lead, antimony, barium8.1.3.2 Particles with a composition descr
47、ibed in section8.1.3.1 may also contain one or more of only the followingother elements: silicon, calcium, aluminum, copper, iron(trace), sulfur (trace), phosphorus, zinc, nickel (in conjunctionwith copper and zinc), potassium, chlorine, tin, and zirconium.8.1.4 Particles with compositions consisten
48、t with GSR willhave one of the following elemental profiles:8.1.4.1 Barium, calcium, silicon (with a trace of sulfur)8.1.4.2 Antimony, barium9(with no more than a trace ofiron or sulfur)108.1.4.3 Lead, antimony8.1.4.4 Barium, aluminum (in the absence of sulfur)8.1.4.5 Lead, barium8.1.4.6 Lead8.1.4.7
49、 Antimony8.1.4.8 Barium (in the absence of sulfur)8.1.4.9 Particles with the above compositions may alsocontain any one or several of the elements listed in 8.1.3.2.8.1.5 Particles with compositions consistent with GSRfrom different kinds of “lead-free” ammunitions11,12includethe following elemental profiles:8.1.5.1 Titanium, zinc8.1.5.1.1 Other elements that may occur include copper ortin (e.g., from jacketing material), silicon, calcium, and alumi-num.8.1.5.2 Strontium8.1.6 Additional classifications may be developed by theanalyst for other kinds of primer compositions and to
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1