Guest Blogger: Lisa Black on Fingerprints

09 Sep


One of the most pervasive and annoying myths of those perpetuated by television shows is that a cop somewhere in Nowheresville, Florida can put an unknown print into his computer and search the fingerprints of anyone who has ever been fingerprinted in the United States, including job applicants and military personnel. This is not true. This has never been true, and is unlikely to become true at any point in the immediate future. Someday, yes, but not in time to make the deadline for your next book.

Here’s how it really works: I am a latent print examiner and CSI for a police department in Florida. I scan in unknown prints (generally called ‘latent prints’) collected at crime scenes or from pieces of evidence. I search those against ‘known’ prints, which are the ten fingerprints and two palm prints collected from each person arrested in my town. I can also do a remote search of the database in the next town, because they are on the same software system. I cannot remotely search the county or state database, because they use different software and though the company has been working on a conversion patch for years, it has not yet been accomplished. However, as of about a year ago we are receiving the known prints for their arrestees—apparently that conversion patch has been accomplished—so I am in essence searching their database, but only the past year’s portion of it. With me so far? I have no access to the state database; when a latent goes unidentified, we make a copy for ourselves and then send the original print off to the state, where some counterpart of mine has to scan it and mark its information and redo all the work that I have already done. All of the county goes to the state, so when the state database is searched we’re also searching the county portion that I have not had access to. We have made hits this way (good!) but it takes four to five months (not so good!).

If all of this sounds like a haphazard patchwork of practices, it is. But Rome wasn’t built in a day, and constantly-improving technology is constantly extending my reach (just as we’ve gone from rotary dials to being able to watch videos of your grandchildren on a phone the size of a slice of cheese).

So who does have that all-seeing national database of fingerprints? The FBI…so to speak. Not because they have a supercomputer with tentacles snaking throughout the computers of every police department in the US, but because every police department sends a copy of the known prints they collect to the feds to enter in their database. They receive all job applicants, too, but it used to be these were only checked via classification system to see if the applicant had a criminal history. Now, reportedly, thanks to the ease of modern technology these prints are also being scanned into a searchable database. It does now have military records, but only since 1990.

And these are only known prints. The FBI cannot search every print from every burglary in the US—no computer is that huge. If I had an entire family slaughtered, or some serial killer at work, then we would pack up the latent prints and contact the FBI with our pleading tale and send the prints off to wait in a queue with the other slaughters from across the country. It would take months, not less time than a commercial break while I sit in front of my monitor (which would be quite unhelpfully flashing the picture of every single print it searches…why exactly it would be wasting bytes on such pointless graphics has always been a mystery to me) sipping coffee and looking sexy in my lab coat. This would not be possible, and not only because lab coats are stiff and bulky and quite untailored. I cannot put in an unidentified latent from Nowheresville, Florida and hit on, say, an unidentified latent from Bupkiss, Iowa, thereby connecting our two crimes…maybe the same killer is at work? I’d better get together with the handsome detective in Bupkiss and do a crossover show…alas, no. Things don’t work that way.

Again, if this all sounds haphazard, it is. You can only work with what you got. Here in my little burg we identify a latent print in 11% of our cases in which usable latent prints are submitted. Considering the vast and sundry circumstances at play, this is an excellent record

So go find your local latent print examiner and give her a hug. I can assure you her job looks so much more glamorous on TV.

Lisa Black spent the five happiest years of her life in a morgue, working as a forensic scientist in the trace evidence lab until her husband dragged her to southwest Florida. Now she toils as a certified latent print analyst and CSI at the local police department by day and writes forensic suspense by night. Her fifth book, Trail of Blood, involves the real-life Torso Killer, who terrorized Cleveland during the dark days of the Great Depression.


9 responses to “Guest Blogger: Lisa Black on Fingerprints

  1. Keith Raffel

    September 9, 2010 at 8:02 am

    Lisa, you mean everything we see on TV isn’t so? As the Marx Brothers used to ask, “Who are you going to believe, me or your lying eyes?” I guess in this case, the answer is going to be you. Terrific post.


  2. Jonathan Quist

    September 9, 2010 at 10:35 am

    Thanks for the visit, Lisa.

    What happens if those far-flung small departments find a link?

    For example, a lead investigator from Nowheresville has a beer with a friend in the FBI, who says “That sounds like a case up in…”

    Or maybe a detective sitting at breakfast bemoaning lack of progress finding the Nowheresville Nosferatu notices the headline on the back of her husband’s sports section, “Bupkiss Bloodsucker Bids Bye-Bye”?

    I realize those are Hollywood scenarios (the cop wouldn’t be drinking with the FBI), but if a tentative connection is established, how strong would it need to be before someone makes a phone call and faxes an enlargement of a print or prints?


    • Lisa Black

      September 13, 2010 at 9:33 am

      Sorry about the delayed response, I’m up in Cleveland for the book tour and can only get on a computer occasionally. I have no idea how long it would take for those tentative connections to add up to something, and I’m sure it depends entirely on the two men talking over the beer. One might go back to his office and immediately look up the case, or he might forget it entirely until three more bodies rack up. But we have no problem mailing a copy of prints or emailing a jpg when requested so that wouldn’t cause any kind of black hole. (We don’t fax except in dire circumstances, and then only as a preliminary. Faxing digitally breaks up the image and reassembles it somehow, so we can’t rely on the accuracy of the fax machine’s reconstruction.


  3. Linda Faulkner

    September 12, 2010 at 10:09 pm


    Great information!

    Care to share how easy or difficult it is to get a set of latent prints at a crime scene?


    • Lisa Black

      September 13, 2010 at 9:37 am

      Difficult in general. I can process entire houses and not get a decent print, especially if the surfaces are dirty, there’s no A/C so it’s humid, or if the burglar only touched items that were upholstered or rough. I need smooth and glossy. Your chances of getting a print are good on stuff that is smooth and glossy, glass, marble, porcelain. The situation deteriorates from there. Other times I’ll stumble on a perfect palmprint on a window or table (people tend to support themselves with one hand as they lean over to unplug your TV or computer). It’s largely a matter of luck. Okay, it’s hugely a matter of luck.


      • Jonathan Quist

        September 13, 2010 at 2:22 pm

        Hmmm… I may be safe. Due to an old wrist injury, if I’m leaning over to unplug the TV, I’m supporting myself on the knuckles of my left hand.

        Which brings up another question – would non-finger-prints have any useful legal status?

        From what you say, they’d be less than useful for _finding_ a subject, because they wouldn’t appear in any of the systems you mentioned. But suppose you got some other biometric data, like lip prints (burglar got hit in the mouth with a 2-liter pop bottle) a partial dental “cast” (he then got hit in the face with a stale birthday cake), the back of a hand (including knuckle wrinkles) where he accidentally slammed it into a wall after wiping the frosting from his face, or footprints, where he staggered across a freshly-varnished floor, blinded by chocolate frosting and in agony over his broken hand. (Yes, this dumb burglar stumbled into Macaulay Culkin home alone…)

        I realize I’m presenting ridiculous examples, but would any of those “non-standard” prints retain any evidentiary value in the presence of a moderately competent defense attorney?


  4. Jonathan Quist

    September 13, 2010 at 2:24 pm

    Uh, by “footprints”, I meant bare footprints.

    Let’s just assume that the home alone kid knew how to use contact cement…


    • Lisa Black

      September 16, 2010 at 4:54 am

      Footprints can be used to identify exactly like fingerprints, except that, of course, they’re not in a database so you would have to have a suspect in mind and a subpoena to get his footprints. Other biometric data–I don’t know. It would all depend on the experience of the examiner presenting the conclusions. They would have to show why the information is specific enough to identify. (Or even exclude–when I did hair and fiber comparisons all I could say is that the questioned and the known samples “could have had a common origin” and could “not be excluded”. There’s nothing wrong with that as long as you’re not misrepresenting the significance of the finding. Unlike on CSI, where they’ll say finding a fiber that matches fibers in the suspect’s shirt ‘proves’ he was there….) The examiner would have to present information to justify his conclusion. It might not be easy but it’s certainly possible.


  5. Jim Keane

    September 20, 2010 at 11:30 pm

    Thank you very much for clearing up a lot of misconception. Of course we know that crimes are not solved quickly – compare CSI with any TruTV show detailing real cases -but it is good to have the point repeated.
    Oh, and I loved the first few words of your bio. Thank you for the good laugh as well as the great explanation.



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