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Poll

Does your lab consider land and groove impression widths as critical measurements?

Yes
8 (7.3%)
No
102 (92.7%)

Total Members Voted: 109

Voting closed: August 02, 2013, 12:40:32 PM

Author Topic: NFEA Research Help - Land and groove impression measurements  (Read 7748 times)

0 Members and 1 Guest are viewing this topic.

Offline Blake Reta

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If you would like, please elaborate on your protocol for land and groove impression widths as critical measurements. Also, please provide what uncertainty (if any) you use when entering your measurements into the GRC database. EX: At the WVSP we will take the average of the measured land impression widths, and a +/- .005 variance to get our minimum and maximum land widths, the same is done for the groove impression widths. 
This information may be used in a research paper for the NFEA.
« Last Edit: July 03, 2013, 01:15:19 PM by Blake Reta »
Blake Reta
West Virginia State Police Forensic Laboratory

Offline Dwight Deskins

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Re: NFEA Research Help - Land and groove impression measurements
« Reply #1 on: July 03, 2013, 01:41:00 PM »
Our system doesn't have a set variance we must follow.  I think this was intended to allow for typically damaged and distorted rifling measurements.
 
Our GRC protocol states "The GRC database is an investigative aid and should not be construed as an all-inclusive list of firearms available with those particular rifling characteristics.  The reported list of possible firearms may be as inclusive as needed based on case details and examiner discretion." 
 
So some analysts choose to use a search range of +/- 0.003" and others use +/- 0.005".  Some analysts may report only the most common firearms, while others report the entire list of possiblities returned.
« Last Edit: July 03, 2013, 01:43:01 PM by Dwight Deskins »
Dwight Deskins
KSP Eastern Regional Crime Laboratory
1550 Wolohan Drive - Suite 2
Ashland, KY 41102
(606)929-9142
FAX - (606)929-9364
dwight.deskins@ky.gov

Offline Lloyd Morse

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  • "I do not judge, I only only answer the questions"
Re: NFEA Research Help - Land and groove impression measurements
« Reply #2 on: July 05, 2013, 09:40:02 AM »
Our lab uses the .05 +/- variance, same as your lab.
 
 
Dfc. Lloyd "Tommy" Morse
Firearms/ Fingerprint Examiner
STPSO Crime Lab
PO Box 1120
Covington, LA 70433
985-276-1227 - office
985-373-8123 - cell

Offline Steve Scott

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Re: NFEA Research Help - Land and groove impression measurements
« Reply #3 on: July 08, 2013, 07:27:03 AM »
Get a rough average then search database with +/- 0.005"
Steve Scott

Offline Blake Reta

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  • Posts: 18
Re: NFEA Research Help - Land and groove impression measurements
« Reply #4 on: July 08, 2013, 03:43:43 PM »
If those who voted in the poll and answered yes would not mind contacting me I would like to ask some additional questions.
304-746-2171
Blake Reta
West Virginia State Police Forensic Laboratory

 

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