Dps crime lab uses photograph of man’s finger in child porn… image database

According to DPS’s website, analysts with the latent prints section "use a variety of techniques –such as carbon powder dusting, super-glue and ninhydrin spray techniques, amido-black print visualization, and argon laser identification — to identify and match prints."

In july 2015, investigators with the texas attorney general’s office reached out to the crime lab to see if the analysts could identify a suspect using only a photograph of the suspect’s fingers, something they’d never been able to do.

"We’ve been asked to do that before. When people take pictures with their cellphones sometimes their finger gets in the way. We’ve looked at those and it’s just not of sufficient quality to even move forward with," said latent prints section supervisor meghan blackburn. "What’s different about this case is the high quality of the actual photographed image."

Entered prints


"We knew we had to do something. We couldn’t just send it back and say we can’t do anything," jenny hall, the latent automated fingerprint identification system (AFIS) supervisor said. "There was a child in immediate danger and it had to be stopped. I knew that if I identified this print I knew I was identifying the person committing the offense because his hand was in there."

Typically the prints they work with are photographed by crime scene technicians and include a measurement scale that helps them calibrate and process the print so it can be entered in the AFIS program.

"We just asked the question: what is the average length of a man’s hand?AFIS program and we were provided a figure based on our research of 7.44 inches. From the base of the palm to the middle finger half of that measurement is the palm itself," blackburn explained. "We don’t have the palm itself but we do have the joints of the finger, at least the distal joint, which we consider the fingerprint itself. So looking at our own hands we can approximate that each of those joints is about a third of that remaining distance so 3.77 inches and then we divided that into thirds for each of those joints and we’re able to draw from the base here to the tip of the finger and then put in that one-third number as our scale."

Entered prints

With the scale in place, blackburn used a program to process the image further, bringing out more details of the ridges. She then turned the processed image over to hall.

"I take a closer look and I actually go through and trace each ridge and plot all the minutia that I see," hall said. "You want to mark as many as you can but a latent is a partial print so there’s sometimes you’re going to have eight (points) or you could have 50 sometimes. I marked quite a bit in this."

Hall then entered the prints into the state’s AFIS program to search it against known fingerprints on file in the statewide database. Unfortunately she didn’t get any matches so she then entered the prints into the FBI’s nationwide AFIS program and left for the day.Hall said

Excited to see what the search results were, hall came to the office early the next morning and pulled up the search which came back with 20 possible candidates as matches.

"It took me less than 60 seconds to know that I had a match. I knew right away just based on the first candidate, looking at the points that I had marked and the points that I was looking for in that known print, that I had a match," hall said.

Hall shared the good news with the investigators at the texas AG’s office who in turn alerted investigators at the georgia bureau of investigation.

"He ended up giving a total confession and gave away a bunch of names of other individuals who were involved in it as well and it’s traveled throughout the U.S.AFIS program with arrests being made," hall said.

For their work on the case hall and blackburn received the FBI’s biometric identification award. They now hope their efforts can be used by other agencies to capture more suspects.

"We do cool things all the time, this is one of the coolest. I think it’s huge. We always thought that we had to have that scale present in an image to do anything, and it does make our jobs easier, but now we know that we can take that chance and enter it and make ids based on an estimate of what size a finger is," hall said. "I hope that (suspects) keep leaving their fingers and hands in photographs that they take like this and I hope they all get arrested."

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