Once a year, forensic labs are required to submit an Annual Accreditation Audit Report to the Laboratory Accreditation Board of the American Society of Crime Laboratory Directors (ASCLD/LAB). This comprehensive assessment ensures that standards are met in regards to various disciplines, and it is the way forensics labs can retain their accreditation with the board.
Implications of Inaccurate Weighing Results
An area of increased attention by ASCLD/LAB auditors has been the compliance of a lab’s weighing equipment. Unless the report specifies performance verification activities carried out by an accredited testing provider, interim lab inspections might occur. Lately, more frequent and detailed monitoring of such activities by auditors has revealed missing minimum weight values.
It may sound trivial, but in forensics, there is no single factor as important as the minimum weight of a balance. Defined as the lower threshold below which results are no longer accurate, this value can be established by an accredited technician using certified test weights. And since the minimum weight value is going to be different for every single balance in a laboratory, it is critical to set a reliable benchmark and appropriately report it in the annual report.
However, if the minimum weight is unknown, a lab’s weighing results of small samples might be inaccurate. Thus, as a provider to the court system, the implications of being just a little off could change a defendant’s prison sentence drastically.
Based on demands for more guidance on measurement uncertainty and minimum weight, METTLER TOLEDO has developed Good Weighing Practice™. This global, risk-based weighing guideline allows forensic labs to produce accurate weighing results while complying with accreditation standards.
Specifically, the newly developed service product - GWP® Verification - provides the kind of comprehensive assessment required by the ASCLD/LAB accreditation board. The core of this performance verification service is a color coded executive summary. It is appropriate for Lab Directors as it illustrates the status of each balance or scale in regards to the potential risks of inaccurate measurements.
Based on this report, specific recommendations for each piece of weighing equipment can be implemented in order to establish the needed tolerance levels and avoid measurements below the minimum weight. Recommendations might include optimal testing schedules including frequencies of checks and calibrations, required test weights and the control limit for each test.
Complimentary Online Risk Check
As a first step, the potential for inaccurate measurements in a forensic lab can be assessed using the complimentary online Risk Check. This tool allows a Lab Manager to determine each balance’s minimum weight value, quickly highlighting where faulty measurements might be occurring.
Next, an external validation by an accredited service provider such as METTLER TOLEDO should be performed. You can expect expert advice on proper performance verification and help on preparing the Annual Accreditation Audit Report.
Finally, the combination of the online Risk Check and GWP® Verification is an easy to implement solution for any forensic lab to satisfy the demands set forth by ASCLD/LAB and to avoid wrong sentencing based on inaccurate sample weights.