Maintenance and Calibration
The Association of Firearm and Tool Mark Examiners (AFTE) provides its members with a set of standard techniques for the maintenance and calibration of stereomicroscopes. While these techniques are not mandatory (unless stated in individual laboratory policy), they are widely used to satisfy the requirements of accreditation standards.
The standards for preparing a stereomicroscope for actual case work are as follows:
- The stereomicroscope will be cleaned, serviced and certified (by a factory certified technician).
- These steps will be documented in the instrument’s maintenance/calibration logbook.
- The stereomicroscope will be standardized utilizing a 100-0.01” division 3x objective. This objective will either be obtained from the manufacturer or have a NIST traceable certificate.
- The microscope may be calibrated with a ruler with divisions of 0.01”. This ruler should also have a NIST traceable certificate.
- This will also be documented in the instrument’s maintenance/calibration logbook.
- For each use:
- The stereomicroscope will be checked to ensure that it is functioning properly.
- This check will be performed by observing an item under the microscope and utilizing past experience to determine if the instrument appears to be giving a true and accurate representation of the evidence.
- This check does not need to be documented.