1、Designation: E 1588 08Standard 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 of
2、 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.1. Scope1.1 This guide covers the analysis of gunshot residue (GSR)by scanning electron microscopy/energy-
3、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 analysis is controlled by pre-set software functions.1.
4、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 does not purport to address all of thesafety concerns, if
5、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 applica-bility of regulatory limitations prior to use.2. Summary of Practice2.1 From the total population of particles collected, thosethat are d
6、etermined by SEM to be within the limits of certainparameters (e.g., atomic number, size, or shape) characteristicof or consistent 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
7、 is obtained from each. The EDS elementalprofile is evaluated for constituent elements that may identifythe particle as being characteristic of or consistent with GSR.3. Significance and Use3.1 This document will be of use to forensic laboratorypersonnel who are involved in the analysis of GSR sampl
8、es bySEM/EDS.3.2 SEM/EDS analysis of GSR is a non-destructive methodthat provides2,3both morphological information and the el-emental profiles of individual particles. This contrasts withbulk sample methods, such as atomic absorption spectropho-tometry, neutron activation analysis, inductively coupl
9、edplasma atomic emission spectrometry, and inductively coupledplasma mass spectrometry, where the sampled material isdissolved or extracted prior to the determination of totalelement concentrations, thereby sacrificing morphological in-formation and individual particle identification. In addition,x-
10、ray fluorescence spectrometry (XRF) is a bulk analysistechnique that has been used for the elemental analysis of GSR.Unlike the solution-based bulk methods of analysis, XRF isnondestructive; however, XRF still does not provide morpho-logical information and is incapable of individual GSR particleide
11、ntification.4. Sample Preparation4.1 Once the evidence seal is broken, care should be takenso that no object touches the surface of the adhesive SEM/EDSsample collection stub and that the stub is not left uncoveredany longer than is reasonable for transfer, mounting, orlabeling.4.2 Label the sample
12、collection stub in such a manner that itis distinguishable from other sample collection stubs withoutcompromising the sample; that is, label the bottom or side ofthe stub.4.3 If a non-conductive adhesive was used in the samplecollection stub, the sample will need to be coated to increase itselectric
13、al 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 interfere with X-ray lines of interest. Furthermore, withEDS syste
14、ms 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 athicker coat. If the carbon coating thickness is not measured,the
15、n its effectiveness in reducing sample charging to anacceptable level should be confirmed prior to analyzing evi-dentiary samples.1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition
16、approved March 15, 2008. Published April 2008. Originallyapproved in 1994. Last previous version approved in 2007 as E 1588 07e1.2Krishnan, S. S., “Detection of Gunshot Residue: Present Status,” ForensicScience Handbook, Volume I, Prentice Hall, Inc., Englewood Cliffs, NJ, 1982.3Wolten, G. M., Nesbi
17、tt, 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 C700, West Conshohocken, PA 19428-2959, United St
18、ates.5. Sample Area5.1 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 part
19、icles 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.3,45.2 When an automated SEM/EDS system is employed,data collection from the
20、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 systems.6.
21、 Instrument Requirements and Operation6.1 General:6.1.1 Most commercial-grade SEM/EDS systems should beadequate for GSR analysis.6.1.2 Automated data collection of GSR involves someportion of the data collection being controlled by pre-setsoftware functions. The extent to which the SEM and EDSsystem
22、s communicate and are integrated varies according tothe manufacturers involved and the capabilities of thehardware/software architecture.6.1.3 A protocol should be established to confirm optimaloperating parameters on a routine basis.6.1.3.1 The EDS energy calibration and beam current sta-bility sho
23、uld be monitored regularly.6.1.4 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 analysis5.6.1.5 A st
24、ub that has not been used for collection (negativecontrol) should also be included with each sample set analyzed.6.2 Scanning Electron Microscope (SEM):6.2.1 The SEM, operating in the backscattered electronimaging mode, must be capable of detecting particles down toat least 0.5 m in diameter.6.2.2 T
25、he SEM must be capable of an accelerating voltageof at least 20 kV.6.2.3 Automated systems will also include:6.2.3.1 a motorized stage6.2.3.2 automated stage control with the ability to recallstage locations of particles for verification6.2.3.3 particle recognition software6.3 Energy Dispersive Spec
26、trometry (EDS):6.3.1 Detector:6.3.1.1 The detector window may be constructed either ofberyllium or organic “thin” film6.6.3.1.2 The detectors resolution should be better (less) than150 eV, measured as the full width at half the maximum heightof the Mn Ka peak.6.3.1.3 The detector must be capable of
27、resolving clearly theBa La1,Lb1, and Lb2peaks.6.3.2 Display:6.3.2.1 A calibrated, scaled display of X-ray energy versuscounts.6.3.2.2 The ability to identify and label X-ray lines and afacility for hard copy output of the display contents.6.3.2.3 At a minimum, the display should be set to 1024channe
28、ls at 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.6.3.2.4 Display of the EDS output must encompass thex-ray lines of analytical utility, with a minimum range of 0-15k
29、eV.6.3.3 Automated systems will also include:6.3.3.1 software capable of acquiring for a specified collec-tion time or total counts and storing EDS spectra from multiplepoints on the sample collection stub.6.4 Sample Placement:6.4.1 For identification purposes, each sample collectionstub should cont
30、ain a permanent or indelibly labeled identifierwhich can be used to reference the stub location on themicroscope stage.6.4.2 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
31、 bedevised 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
32、in cross-section).6.5 Detection and Calibration:6.5.1 Particles of GSR are detected by their backscatteredelectron signal intensity. The absolute signal intensity that aparticle produces is related to the electron beam current, meanatomic number, and size of the particle (for particle sizes on theor
33、der of the beam diameter). Particles whose mean atomicnumbers are high will appear brighter than those of lower meanatomic number composition.As the beam current increases, theamount of signal each particle produces also increases7.6.5.2 The brightness and contrast settings of the backscat-tered ele
34、ctron detector system determine the limits of detectionand discrimination of particles whose mean atomic number4Halberstam, R. C., “A Simplified Probability Equation for Gunshot PrimerResidue (GSR) Detection,” Journal of Forensic Sciences, V36, N3, pp. 894897,1991.5A reference sample should have bee
35、n 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 (caliber ofweapon, ammunition manufacturer, number of rounds fired, collected area fromshooter or a synthetic GSR stand
36、ard. Additional environmental particles may beadded to ensure the inclusion or exclusion of particular classes of particles.6A beryllium window absorbs X-ray energies below about 1.0 keV; therefore,elements below sodium (atomic number 11) are not detected; other windowmaterials may be employed (sing
37、le window light element detectors).7Goldstein, J. I., Newbury, D.E., Echlin, P., Joy, D.C., Lyman, C.E., Lifshin, E.,Sawyer, L., and Michael, J.R.; Scanning Electron Microscopy and X-Ray Mi-croanalysis, 3rd Edition, Kluwer Academic/Plenum Publishers, 2003.E1588082exceed the minimum setting but fall
38、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 analysis. This calibration sample should,if possible, be in the microscope
39、chamber at the same time asthe questioned samples to be analyzed.6.5.3 The backscattered electron detectors brightness andcontrast should be set to include those high atomic numberparticles of interest and exclude low atomic number particlesthat are not of interest. Typically, high contrast and lowb
40、rightness 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 compatible with thenew conditions and should be readjusted. The beam currentmay
41、 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.7. Data Analysis7.1 Definition and Classification7.1.1 Morphologically, GSR particles detected and analyzedusing this m
42、ethod 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 size2. It is not consistent with the mechanismsof GSR formation to find particles with crystalline morphol-ogy. Since morph
43、ology can vary greatly, it should never beconsidered as the only criterion for identification of GSR.7.1.2 The most definitive 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
44、 consistent with GSR is to compare the elementalprofile of the recovered particulate with that collected fromcase-specific known source items, such as the recoveredweapon, cartridge cases or victim-related items whenevernecessary. GSR particles with non-routine elemental profilesincluding the presen
45、ce of additional elements (not listed in7.1.3, 7.1.4, and 7.1.5) may be encountered in case work. Suchparticles can be considered characteristic of or consistent withGSR (as defined in 7.1.3, 7.1.4, and 7.1.5) provided that thepresence of these additional elements can be accounted for bycase-specifi
46、c sources, such as by the analysis of cartridges orammunition/weapon test fire deposits. The relative quantity ofthese other elements and their distribution in the GSR particlepopulation should be consistent between the questioned andknown source samples.7.1.3 Particles with a composition characteri
47、stic of GSRwill have the following elemental profile:7.1.3.1 Lead, antimony, barium7.1.3.2 Particles with a composition described in section7.1.3.1 may also contain one or more of only the followingother elements: silicon, calcium, aluminum, copper, iron(trace), sulfur (trace), phosphorus, zinc, nic
48、kel (in conjunctionwith copper and zinc), potassium, chlorine, tin, and zirconium.7.1.4 Particles with compositions consistent with GSR willhave one of the following elemental profiles:7.1.4.1 Barium, calcium, silicon (with a trace of sulfur)7.1.4.2 Antimony, barium8(with no more than a trace ofiron
49、 or sulfur)97.1.4.3 Lead, antimony7.1.4.4 Barium, aluminum (in the absence of sulfur)7.1.4.5 Lead, barium7.1.4.6 Lead7.1.4.7 Antimony7.1.4.8 Barium (in the absence of sulfur)7.1.4.9 Particles with the above compositions may alsocontain any one or several of the elements listed in 7.1.3.2.7.1.5 Particles with compositions consistent with GSRfrom different kinds of “lead-free” ammunitions10,11includethe following elemental profiles:7.1.5.1 Titanium, zinc7.1.5.1.1 Other elements that may occur include copper ortin (e.g., from jacketing material), silicon, calcium, and alumi-num.7.1.
