Thursday, April 26, 2012

Pikes Peak Writers Conference 2 - Fingerprinting

What I'm reading: Free Fire, by C.J. Box; The Immortal Life of Henrietta Lacks, by Rebecca Skloot (book club)

Continuing with workshop recaps from the Pikes Peak Writers Conference.

There were two workshops on forensics, both given by retired forensics expert, Tom Adair. (And, he's going to be my guest on May 8th). Both were "hands on" which made a great change from sitting and taking notes.

The first was about fingerprinting. (And although the workshop was hands on, he did begin with some facts.)

Fingerprints are unique and permanent (with very few exceptions, such as burns. They're established in the second trimester, pre-birth. In addition to fingerprints, all dermal ridge prints are unique to the individual (feet, toes, palms, etc.)

Contrary to what we might believe from television, prints are NOT everywhere. And, not finding someone's prints on an object doesn't mean the person didn't touch it. Finger marks are more common, but they're not usable for identification. Probably fewer than 10% of fingerprints found at a crime scene are identifiable to someone. It's not likely you'll get prints from bullet casings.











And speaking of identification—when prints are sent through the computer system, the results are NOT the names of their owners, complete with pretty pictures. They get back a list of "likely matches" and they're numbered. Eliminates any bias on the part of the examiner who might have a suspect in mind.

The quality of fingerprints is affected by environment. Here in Colorado, it's a very dry climate, and since fingerprints are mostly water, we don't leave as many as we would in a more humid environment. Also, as people age, their skin tends to dry out and become more brittle, so again, the quality of prints deteriorates. On the flip side, prints of prepubescent children don't last long on surfaces.

Most law enforcement officers are trained to lift prints using black powder, but the more sophisticated tests are done back in the lab.


Once Tom filled us in on background information, he turned us loose on his collection of things to print, and tools for printing. We had access to black fingerprint powder, magnetic powder, powders that fluoresced, and a collection of things he'd fumed with super glue. We discovered relatively quickly that he wasn't kidding. It wasn't easy for us to find prints, even when we were the ones making them and knew exactly where they were. To get my prints on a plastic fast-food cup, I first made sure I touched my fingers to my face (to pick up extra oils), and then planted them firmly on the cup. After that, Tom lifted them using tape and put them on a card.



The other important piece of takeaway information was that law enforcement is always looking to create a triangle, connecting the victim, the suspect, and the crime scene.

The second workshop was about forensics in 1875. Quite a difference. I'll have my recap of that one another time.

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12 comments:

Terri said...

Very interesting. Thanks, Terry.

Darcy Flynn said...

Thanks for the post. I love stuff like this. :)

Nikki Barnabee said...

With so many CSI TV-inspired ideas in our heads, it's always good to hear details that are the real deal. Esp. for crime/thriller writers like me :-)

I look forward to the post about forensics in 1875. I know I was fascinated by the novel The Alienist, which took place a bit later than that. Thanks for sharing!

Marian L said...

Thanks, Terry
I always get so much useful information on your blog, Marian

Sonya said...

Great post. Thanks for sharing.

Larissa Reinhart said...

Fascinating! Thanks for sharing. I also learned a lot from The Alienist. The part about how climate effects prints was really interesting.

Karen C said...

I bet this was a great workshop. I recently had to have my prints taken for a CHL and they were done electronically. My prints were initially rejected because my hands were too dry. (I'm thinking - how can you 'fail' a fingerprint test??) Poor guy taking my prints was trying to be so politically correct in explaining that as we get older out hands dry out. ;o)

Terry Odell said...

Thanks to all - glad you find my posts worth a few moments of your time. Karen - I had my prints done by LiveScan in Orlando, and the tech was inexperienced. Took her about 20 minutes, and a lot of them she gave up and just overrode the computer's rejection so I really don't know if they got a useful set.

Craig Faustus Buck said...

Thanks, Terry. I remember having a fingerprint kit when I was a kid. They sold them in toy stores. Drove my mother nuts to find black dust all over the place LOL.

Cassandra L Shaw said...

Great post terri. I'm going to print that info out and put it in my forensics research file.

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Kathleen Mix said...

Sounds like a fascinating workshop. So much of what we see on TV is fantasy.
I took a tour of our local forensics lab with a Sisters in Crime group and the information has been invaluable.
Thanks for sharing the things you learned.