Gunshot Residue Analysis (GSR Testing)
McCrone Associates has been performing gunshot residue (GSR) analyses for more than 25 years — first using electron microprobes (EMPA) and more recently scanning electron microscopes (SEM) equipped with energy dispersive X-ray spectrometry (EDS) detectors for elemental composition of materials.
For the last 15 years, McCrone Associates has used these instruments in an automated mode. We follow the most current version of ASTM designation E1588 “Standard Guide for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive Spectrometry” for our GSR analysis.
Please note that McCrone Associates only accepts GSR projects from attorneys (prosecutor/plaintiff and defense) or government law enforcement agencies. Retainer fees may be required. Requests from non-legally represented individuals will not be accepted.
Currently accepted materials for GSR analysis are:
- Commercial GSR Collection kits for SEM analysis
- Evidentiary clothing items
- Evidentiary cotton tipped swabs
- Evidentiary clear tape adhesive strips
Commercial GSR Collection kits for SEM analysis typically contain two, three, or four SEM tape lift stubs. For such kits, the current cost for photo-documentation and SEM/EDS analysis is $500 per stub.
For evidentiary clothing items we charge an hourly rate of $385 for photo-documentation and tape lift sampling using commercial GSR collection kit SEM tape lift stubs and then charge $500 per stub for the SEM/EDS analysis. Cost estimates will be provided upon strategy discussions with the McCrone GSR analyst to determine the quantity of tape lift stubs required.
For cotton tipped swabs and clear tape adhesive strips we photo-document and then ash the samples in individual covered ceramic crucibles for two hours at 500°C. Then we conduct tape lift sampling from the bottom of the crucibles by using commercial GSR collection kit SEM tape lift stubs. The hourly rate of $385 applies for this phase of the work and then the rate of $500 per stub applies for the SEM/EDS analysis.
Using automated analysis software we scan approximately 95% of the total surface area of the SEM stubs in search of characteristic GSR particles produced from the primer cap compounds, i.e., particles containing lead (Pb), barium (Ba), and antimony (Sb). The GSR particles are located in the SEM by grey-level threshold limits and then analyzed for elemental composition using the (EDS) detector. The EDS spectra from all detected particles are automatically stored for interpretation and future documentation needs. 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 spheroidal/ellipsoidal or irregularly shaped with molten appearance).
After the automated analysis has been completed, characteristic GSR particles are relocated for manual SEM electron micrograph imaging and confirmatory EDS analysis.
Our turnaround time is preferably 20–25 business 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 5–10 business 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 for an additional charge at hourly rates. 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. Our staff members are paid on a salary basis and therefore are not driven by quotas or personal monetary gain 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.