Validation Studies

[clorenzo]

I am working on performing retroactive validation studies on all procedures we are currently performing and would like some feedback and assistance from others.  For the comparative type of procedures (firearm, tool mark) we were thinking of using our results we obtained from participation of the annual CTS proficiency tests (gathering only our test results), but wanted to know how others have addressed this.  Also, if someone would not mind sharing how they have written up a validation study, that would really help.

[Greg Klees (CB)]

Hi Cindee,

Hope all is well with you.  Regarding your use of validation studies in the FA/TM ID discipline, you can use 1) internal CTS proficiency test results from within your lab or lab system only, 2) external CTS results for the entire discipline 3) your personal CTS proficiency test results and/or 4) the controlled validity error rate studies listed in the ARK, Appendix I Power Point, around slide #54.   

When using CTS proficiency tests, calculate your results for error rates by the same mode used Steve Bunch and Doug Murphy as listed under the ARK, Error Rate link. If you have questions on their re-calculations, I'd contact one of them. 

Lastly, you should know the error rate of your lab and your personal error rate on proficiency tests are questions that are being asked more frequently in court. 

Hope this helps. If not, contact me for additional suggestions and referrals.

-Greg Klees