MadSci Network: Other

Re: If a fingerprint is photographed using a digital camera.

Date: Wed Jun 25 08:50:15 2008
Posted By: Dale L. Laux, Staff, Serology/DNA, Ohio Bureau of Criminal Identification
Area of science: Other
ID: 1214383813.Ot

Hello Dave,

Good question. I strolled down to our Latent Prints section of the lab and discussed your question with some of the analysts. There are two schools of thought. Some old timers still choose to compare prints 1:1 and use a magnifying glass. But by using the magnifying glass, you are magnifying the image, so 1:1 is now 20:20 for example. With the new technology abvailable, some analysts prefer to use a visual comparator which magnifies both the latent print and the fingerprint card to the same extent.

Regardless of how the analysis is done however, digital photographs are taken with a ruler in place. In this way, any image that is magnified will have the ruler magnified as well and 1 mm will still represent 1 mm. Any small variation that exists between rulers will be inconsequential as latent print examiners are looking for general characteristsics, loops, whorls, etc. and then unique detail and not necessarily measuring a distance between ridges as this may vary due to surface conditions, weather conditions, pressure applied in making the latent print, etc.

Best regards,

Dale L. Laux
Forensic Scientist

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