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BOSTON Police Department Crime Laboratory Amy Reynolds, Erin Corcoran, Emily runt

Instrumental Validation of a Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM/EDS). BOSTON Police Department Crime Laboratory Amy Reynolds, Erin Corcoran, Emily runt. SEM/EDS Acquisition. Sept. of 2014 our previous Amray SEM with PGT EDS stopped working

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BOSTON Police Department Crime Laboratory Amy Reynolds, Erin Corcoran, Emily runt

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  1. Instrumental Validation of a Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM/EDS) BOSTON Police Department Crime Laboratory Amy Reynolds, Erin Corcoran, Emily runt

  2. SEM/EDS Acquisition • Sept. of 2014 our previous Amray SEM with PGT EDS stopped working • After much research and soliciting for funds • JEOL IT300LV SEM with an Oxford X-MaxN 50 EDS • Purchased in 2016 • AZtec software • Trace Evidence analysis • Paint • Tape • Glass • General Unknowns • Gunshot primer residue analysis

  3. SEM/EDS Validation • ANAB 17025 Accreditation • 5.4.5, Supplemental and our own labs validation requirements • Spoke to several Forensic Scientists in the field about their validations • John Druggan, MA State Police Crime Laboratory • Matney Wyatt, US Army Criminal Investigation Laboratory • Sent their validation plan for validating an SEM/EDS for GSR • David Edwards, JEOL • Richard McLaughlin, Oxford Instruments • Started out with validation of the instrument for trace evidence samples other than Gunshot primer residues

  4. Magnification and Measurement Tools • Copper Grid (200 Mesh, Pelco XCS-6 Standard) • 3 locations on grid • One edge of the mesh to the adjacent edge • 2 magnifications (350x and 550x) • JEOL and Oxford image • Average measurements from the 3 locations at each magnification, compared to expected 127µm grid spacing • JEOL- 350x was 126.8µm • JEOL- 550x was 127.6µm • Oxford- 350x was 126.9µm • Oxford- 550x was 126.6µm • Under 1µm difference observed was acceptable

  5. Verify Factory Resolution –127kV for Mn • Manganese (Pelco XCS-6 Standard) • FWHM • Process Time 4 and 6, 20kV • Determine height of K peak, left side of peak at half height subtracted from right side of peak at half height • Number of channels counted at half width, multiplied by the amount of eV’s per channel • Average of 3 spectra for each method determined • Process time 4: approx. 133eV • Process time 6: approx. 127eV • Protocol-Process time 6 is used, any eV under 127eV is acceptable for QC, or +/- 10eV of 127eV Height FWHM

  6. Verify X-ray Range • Full Scale Verification • Molybdenum (Mo) aperture • 3 spectra at 30kV • Mo peaks observed at approx. 2.3keV (2.266keV) & 17.5keV (17.446keV) • Low eV Limit Verification • Boron (Pelco XCS-6 Standard) • 3 spectra at 20kV • B peak observed at 0.179keV (0.179keV) • Beam Energy Range • Manganese (Pelco XCS-6 standard) • 1 spectra each at 20kV & 25kV • Bremsstrahlung Curve observed to drop off at approx. 20kV (20kV run) and 25kV (25kV run)

  7. Verify Consistency of Probe Current • Manufacturer-Probe current over the course of a run <1% difference per hour • Current meter was purchased • rbd 9103 AutorangingPicoammeter • Old aperture placed over the top of a hole in stub holder (Faraday cup) • Focused upon the aperture hole and magnified until the aperture hole completely covered field of view • Filament stabilized for ½ hour • Probe current data collected for 9.69 hours • Difference in probe current data over 9 hours was approx. 2.6% • <1% per hour, 0.28% per hour

  8. Old vs. New • Do we get the same or better results with the new SEM/EDS vs. the old SEM/EDS? • Used old proficiencies to answer this question • Tape- 2010 Items 1 and 2 (electrical), 2012 Items 1-3 (duct) • Paint- 2012 Items 1-3 (automotive), 2013 Items 1 and 2 (architectural) • Glass- 2011 Items 1 and 2, 2012 Items 1 and 4 • Determine the best parameters • Used different Pa in Low Vacuum (LV) mode (30, 50 and 70) • Observed charging at low Pa • Observed contamination from other paint layers or the environment at high Pa due to beam spread • Used different kV (10, 15, and 20) • Unable to obtain all of the elements found in previous spectra with lower kV • Observed contamination from the other paint layers or the environment with higher kV • Determined that the samples needed to be sputter coated with carbon

  9. Carbon Sputter Coating • Denton Vacuum Desk II Sputter/Etch Unit and Carbon Evaporation accessory • Resurrected and sent off for maintenance • Determine the best height of the carbon chuck for proper carbon coating • Heights- (5.5, 7.5 and 9.5 centimeters above the samples) • Higher the carbon chuck the lighter the coating • Lower heights could burn the sample • 7.5 cm height chosen • Slight charging still observed on the electrical tape and backing of duct tape • Carbon coat twice or use low Pa in LV mode

  10. Proficiency Comparisons • Glass Proficiency • CTS 11-548 and CTS 12-548 old system vs. new system • All the same major peaks observed • Paint Proficiency • CTS 12-546 old system vs. new system • Same major peaks observed plus more peaks with new system • Better Quality Detector • CTS 13-546 old system vs. new system • Same major peaks observed • Tape Proficiency • FTS 10-Tape and FTS 12-Tape old system vs. new system • Same expected peaks observed plus more peaks with the old system • Contamination

  11. Protocol for SEM/EDS • JEOL SEM with Oxford EDS was comparable with the reliability, reproducibility and sensitivity to the old Amray SEM with PGT EDS • Protocol adjustments • Daily QC • Mn is run at 10mm, 20kV, Aperture 3, Process Time 6 • FWHM at 5.9eV should be below 127eV, but at least within +/-10eV from 127eV • Charging samples • May use LV mode below 30Pa, starting at 15kV • Highly recommended to carbon coat the samples • If after carbon coating the sample charging is still observed: • Increase the working distance (possible loss of elemental information) • Decrease the accelerating potential (possible loss of elemental information) • Recoat the sample with another layer of carbon (best option) • Parameters to start: • 10mm, 20kV, Aperture 3, Probe current at a level to observe 40-50% deadtime, Secondary detector for good image quality, Backscattered detector-Compositional for good elemental analysis

  12. Gunshot Primer Residue Validation • AZtec software • Seems like all other labs with Oxford are using INCA software • ENFSI/PLANO standard • Determine the best parameters to be used • 90% of the >1µm particles • 10mm, 20kV, Process time 4, Aperture 2, these parameters stayed the same • Gray level threshold changes first • 8000, 8800, 9000, 10000 at 3µs first pass • First pass µs changed second • 5, 4, 3, 2, 1 µs at 8800 gray level threshold • Magnification changed last • 190x, 250x

  13. Gunshot Primer Residue Validation • Each different parameter run was done in at least triplicate • Data from the runs were exported to Excel • X and Y coordinates were plotted to create an overlay on the PLANO standard plot • Determine the % of the particles >1µm • After countless runs with the different parameters using the PLANO standard • Several discussions and visits with both Dave Edwards (JEOL) and Richard McLaughlin (Oxford Instruments) • We got the best parameters for a Gunshot primer residue run nailed down • 10mm, 20kV, Aperture 2, Process time 4 • Image Scan size: 2048, Dwell time: 2µs, Gray level threshold: 8800 • Second pass imaging: 20µs, Acquisition mode: Live Time of 0.5s, Second Pass EDS filter: Lead containing features with an additional time of 1.5s • 250x magnification

  14. Negative Control Study • 5 air blank samples using the optimum parameters • 5 lab spaces, SEM stubs were left open for 3 working days • Serology lab, pre-SEM room, SEM room, Trace lab, Evidence Receiving area • Results • Zero characteristic GSR particles found on any of the stubs • Some consistent GSR particles found • Found on the actual aluminum stub surface not the adhesive tab • Negative control • Air blank from the SEM room or pre-SEM room (sample prep area)

  15. Known GSR stub • Stub collected directly after shooting occurred • Test the optimum parameters • Stopped after 100 characteristic particles detected • Test the reacquisition portion of the software • Change to GSR Reacquisition Program • 15 features ranging from 20µm to 1µm were reacquired-Automatically • Confirmed 3 features >9µm in size • Determined that if feature is <8-9µm in size it will not relocate properly to those features • Point and ID as an end around • Unacceptable • Version 3.4 now has a Manual Reacquisition

  16. Known GSR stub • Version 3.4 was installed in Nov 2017 • Manual selection inthe GSR Reacquisition program • Relocate to a feature • Magnify and focus on this feature • Enter this magnification into the program • Start reacquisition • Need to find and refocus on the particle at the previously determined magnification • Reacquires a better image and spectrum • 10mm WD, 20kV, Aperture 2, Process Time 4 • Image Scan size: 512, Dwell time: 5µs, Gray level threshold 5000 • Acquisition mode: Live Time of 10s • Confirm the reacquired features • Create a report

  17. Weapon and Time of Collection Study • Currently running analysis on a weapon and time of collection study • 5 different weapons, 5 different shooters • Glock 9mm pistol with PMC bronze FMJ 9mm Luger • Smith & Wesson 38 revolver with PMC bronze FMJ 38 special • Hi Point 9mm pistol with Federal American Eagle FMJ 9mm Luger • Walther 380 auto pistol with Winchester FMJ 380 Auto • Ruger 357 Magnum revolver with Blazer Total Metal Jacket 38 Special + P • 4 different times since collection • 0 hrs, 2 hrs, 4 hrs and 6 hrs after shooting

  18. Preliminary Results-Weapon and Time of Collection Study Shooter #1- Glock 9mm pistol

  19. Preliminary Results-Weapon and Time of Collection Study Shooter #2- Smith & Wesson 38 Revolver

  20. Contamination Study • Prep area with the Denton Vacuum was used as our GSR Distance Determination area previously • Adjacent to the SEM room • Since been moved to another location in the lab • Stubs were collected from the lab bench, fume hood and examination table • Before cleaning • After cleaning • Determine if any contamination is observed from these locations for future casework • Clean again? • Retest areas with further stubs?

  21. Training Program • Training Courses • JEOL JSM-IT300LV operator’s training course • Oxford AZtec operator’s training course with AZtec GSR • Gunshot Residue Identification-Wayne Niemeyer, Hooke College • Readings • ASTM Standard Guide for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry (newest version) • SWGGSR Guide for Primer Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry • Summary of the FBI Laboratory’s Gunshot Residue Symposium, 2005 • Related journal articles • Workshops • Studies using brake pad stubs and fireworks stubs • Run 2-3 of the Time of Collection sets • Old proficiency test(s) • Competency • Practical- Old proficiency or a Mock case created for our analysts • Theoretical- Competency questions and Mock trial

  22. Thank you • MatneyWyatt • US Army Criminal Investigation Laboratory • John Druggan • Massachusetts State Police Crime Laboratory • Rusty White • Texas DPS, Austin Crime Laboratory • Mike Martinez • Bexar County Crime Laboratory • Dave Edwards • JEOL • Richard McLaughlin • Oxford Instruments • Everyone else in the SEM/EDS and GSR community

  23. Questions?

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