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McCrone Associates has been performing gunshot residue (GSR) analyses for more than 20 years first using electron microprobes (EMPA) and more recently scanning electron microscopes (SEM), For the last 10 years, McCrone Associates has used these instruments in an automated mode. Currently we follow the ASTM designation E-1588-08, “Standard Guide for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive Spectrometry” for our GSR analysis.
Analyses
Using automated analysis software we scan approximately 90% of the total surface area of the SEM stubs (e.g., provided in the SEM GSR kits) in search of telltale GSR particles produced from the primer cap compounds. The GSR particles are located by grey-level threshold limits and then analyzed for elemental composition using the energy dispersive x-ray (EDS) detector. The EDS spectrum of interesting particles is automatically stored for interpretation and future printouts. The quantification of the detected elements is provided with each EDS spectrum. In addition, the analyses provide particle shape, and size (ECD – equivalent circular diameter) measurements which are used to further characterize GSR particles (usually <5 µm and spherical shape).
After the automated analysis has been completed, the GSR particles can easily be relocated and SEM electron micrographs obtained for documentation.
Cost for Analyses
The cost of automated GSR analysis and photo documentation is $400 per stub. Please note that some GSR collection kits contain three stubs (right hand, left hand, face) and others contain four stubs (right palm, right back, left palm, left back); therefore, the analysis cost per kit is $1,200 or $1,600. We recommend that you prioritize the order of the analysis by stub and collection area. Thus, as we proceed with the analysis we will inform you of the results from the analysis of each stub. This gives you the opportunity to decide if you want the analyses done on the remaining stubs.
Our turnaround time is normally within 10 - 15 working days. However, occasionally there is a need for the results on a RUSH basis. For these rush projects we will try to accommodate your needs, but they are charged at a premium rate of twice the regular cost. Turnaround for rush projects is 3 - 5 working days. If, for any reason, we cannot complete the analysis on a rush basis and require more time (e.g. due to the number of analyses requested or due to higher priority projects), we will charge the analyses at regular rates.
Expert Witness Services
As part of our services we also provide expert witness or court testimony at an additional charge. Hourly rates will be quoted upon request. The client is also responsible for any necessary travel or miscellaneous costs associated with the analyses or consulting (e.g., airfare, per diem, car rentals, photo documentation/displays for court testimony, etc.).
McCrone Associates is an independent laboratory and our staff members are paid on a salary basis. Therefore, the staff is not driven by quotas or personal monetary gains for performing analyses and giving expert testimony. Each staff member takes pride in providing accurate, impartial and unbiased analysis and opinions. In legal cases, we perform analyses and consult for the prosecution or the defense and occasionally both sides, if mutually agreed upon.
Key Services
Common Examples
- Particle identification
- Bullet residue analysis
- Clothing analysis
- Hands and face sample analysis