 Mystery: October 25, 2006 Issue [#1345] |
  Mystery
This week: Edited by: Tehanu  
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Training is everything. The peach was once a bitter almond; cauliflower is nothing but cabbage with a college education. ~ Mark Twain's Pudd'nhead Wilson
Experience is the foundation of superior problem-solving ability in all professions; in latent print identification it is the hone for sharpening all essential skills. ~ Robert D. Olsen, Sr., Identification of Latent Prints |
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As Outasync reminded me, Mark Twain's Pudd'nhead Wilson was a story not only about slavery and stereotypes but also about fingerprinting and the eccentric town detective who liked to take prints on glass plates. This story, published in 1894, hints that it is quite possible that Twain read Henry Faulds' report on fingerprinting and its potential use in solving crimes. Ironically, Faulds was considered by many to be nutty - the Scotland Yard refused his offer to fund and instate a fingerprint lab for them. It was not until a much more wealthy and powerful member of society, Francis Galton, spoke up about the usefulness of fingerprinting in collaring criminals that the police and government gave much thought to the idea. Hence, my mind turns to another Pudd'nhead quote:
"The man with a new idea is a crank until the idea succeeds."
Fingerprinting obviously caught on - - and this week's newsletter will cover how to fingerprint, lift prints, and compare prints. There are many ways to go about all three, so I will be covering the more popular ways I came across in my research.
(Warning - most information is based on American and British information. Each country does things a bit differently and has different laws concerning comparison of prints and presenting evidence in court.)
How To Fingerprint
If looking to get fingerprinted for a job or for safety purposes, or if you are a criminal about to be "booked," a police officer will take your prints at the police station. All that is really necessary is a black ink pad and a fingerprinting form (you may have to provide the latter).
 While you are standing parallel to the form, the police officer may ask you to roll up your sleeves and to stay relaxed. She will encourage you look away and not "help" by rolling your fingers on the form.
The form will be clamped to a table or shelf, the clamp framing the form so that each print can be placed in its respective box on the form.
The officer will take your left hand first. She will ink and then roll each finger on the form, from one side of the nail to the other, in turn.
After each finger and the thumb has been rolled, the four fingers get flatly stamped all at once on the bottom portion of the form.
Then it is time to do the same for the right hand.
It is easy to become nervous and sweaty in a police station, especially if you are a criminal. Excessive perspiration will mess up prints, so an astute officer will notice clammy fingers and should dry each finger with a towel before inking and rolling.
If your finger pads are worn or rough, lotion or ridge builder (a sort of cream/gunk) might be applied to your fingers and then wiped off before the fingers are placed on the ink pad.
If you have crippled or webbed fingers, or are missing digits, the police officer will take extra care with prints and may use the form a bit differently. If you have a new scar or cut, the officer will suggest that you come back when it is healed. Unless the skin is cut deeply, the ridges will grow back.
If you have more than ten fingers, the additional fingers will not be rolled, but the extra finger(s) will be noted on back of the form.
If a known criminal is arrested and does not have hands, her footprints should be on file.
A novice or private detective may purchase a fingerprinting kit that should at least include an ink pad, fingerprint cards, and a card strip holder. Other kits may have towelettes, tubes of ink, ink rollers, and tools to ensure accurate prints when dealing with crippled fingers.
 If you are interested in obtaining your own kit, also consider buying a video, taking a class, and/or researching more about the subject. If you have read my first newsletter on fingerprinting, then you know the first officer who took my prints did not do a good job. Those prints were rejected by the FBI and may not have held up in a court of law. Knowledge, experience, and common sense play a role in producing adequate prints.
 The next five paragraphs concern fingerprinting the deceased. Do not read this section if you become easily queasy.
 According to the FBI's 2006 statistics seventy-six percent of the unknown dead were identified through fingerprinting. The bodies located had been deceased anywhere from three weeks to three years. Decomposition may affect the outcome as ridges may become fragile, as well as finer and less pronounced. However, cadavers that have little or no decomposition can be easily fingerprinted.
An investigator who must fingerprint a cadaver can do so. Place the cadaver facedown on the table, with hands stretched out in front, palms down. Then roll the fingers the same way as a police officer.
If rigor mortis is in effect, the inspector can pull straight one finger at a time by firmly grasping the finger and pushing down with her thumb on the attached knuckle.
If there are a lot of wrinkles in the fingers, water can be injected into the finger pads, thus producing a bulge in the flesh. In other instances of obtaining prints from a cadaver, skin has been known to come off - - it may still be useful. The operator may place the skin fragment over her own finger and then ink and print it that way. Know that skin can only be intentionally cut from a corpse after obtaining legal permission.
There are ways to deal with very decomposed or lacerated fingers. The FBI imparts detailed ways to get prints from these cadavers in The Science of Fingerprints. I will not share those findings here. 
How to "Lift" Prints
A visible print is fairly easy to get - by using tape, you can procure the print.
A latent, or invisible print, is harder to obtain. A forensics expert should look for an area at the crime scene that might hold prints. Once an area or object is found that might hold prints, it can be dusted, subjected to chemicals, or sprayed, swabbed, or dipped in ninhydrin or other chemical alternatives.
Powder dusting is the easiest and most popular way to discover prints, however, by brushing the surface, you are irrevocably altering, even in a small way, the fingerprint ridges - the secretion of sweat and fat - that you uncover.
Ninhydrin (and something called NFN reagent) has become more popular, especially with the police. It is very useful when it comes to porous surfaces, like paper and cardboard. Heating a surface or object after placing ninhydrin on it will accelerate the rate at which the fingerprints appear. After application, lasers or x-rays may increase the prints that appear. A bleach solution may also help, especially when it comes to finding prints on bank notes. Ninhydrin prints fade over time and should be photographed quickly after the prints appear.
There is a wide variety of colored powders and reagents that may enhance particular prints. For example, black, violet, and blue protein dyes help enhance bloody fingerprints.
Cyanoacrylate fuming is a way to find prints on diverse surfaces, like Styrofoam, metal, and even skin. To make prints appear on these objects, suspend objects in a fuming cabinet, place two to three drops of cyanoacrylate into a dish and place dish in the cabinet. Fingerprints will appear on the objects over time - you need to watch for their appearance so the prints do not become overexposed.
Superglue and other accelerating procedures may be used in lieu of cyanoacrylate. Each procedure appears to be a little different. Again, lasers enhance the prints after they appear.
How to Compare Prints
There are three particular ridge patterns that can be found on human fingertips: the arch, the loop, and the whorl. There are eight subcategories, such as "plain arch" and "tented arch." Your fingers could potentially hold all these patterns. For instance, your left index finger could have a plain whorl, your left middle finger a tented arch, and so on.
A common way to compare prints is to find and record each print's "minutiae points." Minutiae points are where print ridges come together or end. The five types of minutiae points include:
 Bifurcation (when a ridge splits into multiple ridges, called branches)
Divergance (where parallel points either spread apart or come together)
Enclosure (when a ridge splits into two branches and then quickly comes back together)
Ending (when a ridge ends)
Valley (spaces or gaps on either side of a ridge)
One typical fingerprint may hold between thirty and forty minutiae. The FBI has found that no two individuals share more than eight common minutiae points.
There are different methods used to compare points in separate prints. You could use a grid, compare tracings using a backlight, overlay one copy of a print over another (and use different colors) and so on. The "surest" way of comparing prints, according to Advances in Fingerprint Technology, is by using the "Conventional Method" or identifying "based on the ridge characteristics and their unit relationship to one another." This method allows an expert to match even distorted prints, by comparing points.
Although at least one human expert is needed to compare prints for court purposes, with today's computer technology, databases like the FBI's IAFIS can match prints with 100% accuracy.
In the millions and millions of fingerprints of humans, monkeys, koala bears (and so on) compiled throughout the world, no two prints (for more than one person) have been found to be identical. So, if your print is found smudged on a soda can and compared to a cleaner FBI database print, the minutiae points should determine that the prints are identical and belong only to YOU.
If you are considering writing a story involving fingerprints, I hope you have found this overview helpful. And if you wish to write realistic pieces about fingerprinting, I encourage you to look into finer details and keep up with evolving fingerprint technology.
For those wondering, my second set of fingerprints WERE accepted by the FBI. If you ever need to get fingerprinted for job or safety purposes, I highly suggest you "shop around" and find a forensics expert or an officer who takes a lot of prints and has been doing so for at least a few years. Again, experience is key when it comes to fingerprinting!
Resources:
http://www.fbi.gov
http://et.wcu.edu/aidc/BioWedPages/Biometrics_Finger.html
http://gutenberg.org/files/19022/19022-h.htm
http://en.wikipedia.org/wiki/Fingerprinting
http://www.xs4all.nl/~dacty/country-rules.htm
Advances in Fingerprint Technology (Lee and Gaensslen)
Fingerprints: The Origins of Crime Detection and the Murder Case That Launched Forensic Science (Beaven)
rose_shadow:
Show how a crime scene investigator narrows down suspects based on a bunch of prints at a crime scene.
Show what a smart criminal does at a crime scene including wiping down surfaces and the strategic placement of fake fingerprints.
Breezy-E ~ In College :
A finger of the middle left-hand finger is found on the cash register. Show how the robber was found based on this.
alissaameth:
Three fingerprints (from three different people) are found on a window to a home that has been broken into. Inside the house, a body is found with fingerprints from one person on it. None of the fingerprints on the window match the fingerprints on the body. The only fingerprints that are already in the police database are two from the window. What happened?
werden  :
A suspect's bloody fingerprints are all over the scene of the crime. Show how this person is not guilty even with the evidence. :)
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 I searched, but could not find any mysteries on WDC that included finding or comparing fingerprints. BUT I did discover some interesting reads concerning evidence:
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 Interested in doing something mysterious? While waiting for Halloween to arrive, participate in one of these:
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WDC Member Comments
Thanks for all the feedback! 
Bailey :
Very interesting, I enjoyed your newsletter and look forward to the next.
Thanks! I hope you found this one to be worth the wait!
John~Ashen :
Sometimes investigators get only a "partial" fingerprint. What is the minimum they need to present as evidence in court? (I think I "match" is at least 13 points, though I'm sure they could start looking for suspects with less.)
A frustrating question!  Because it depends on the country in which you live. Some countries, like France, ask for a particular amount of experts and points. I have scoured the Internet, including the FBI fingerprint website, for an explanation on legal court material. I only found two articles, one dated 2002 and another 2006 stating that the United States and the FBI do not ask for a particular amount of points...only one expert witness and a reasonable explanation.
I have called my local police station and am waiting for a more thorough response. If I hear back from an authority figure, I will be sure to post my findings in the next newsletter.
alissaameth:
Excellent newsletter, Tehanu! Thanks!
A question about fingerprinting: Say a guy is convicted of a crime, so his fingerprint is now on record. If he gets a permanent scar on his fingerpad later, can he still be identified by the old fingerprint?
Good question. It depends. If the scar is not too big, and more than eight minutiae points are found to be identical, I would say that he can still be identified. If the scar pretty much obliterates or alters the ridges, he might get away with the crime. Again, it depends...usually more than one print is on file and the FBI could use his other digits to convict him.
Outasync :
Just a point of interest...
In his book "Pudd'nhead Wilson" (published 1894), Mark Twain uses fingerprinting. He has a character who collects finger prints from everyone in town as a hobby. The others view him as a harmless excentric, but his collection of little glass plates changes the whole outcome of the story.
Twain was always on top of current events. That is a great book and I am glad you reminded me of it.
diana
Your research on fingerprinting proves fascinating. I came across the most interesting case; two men with identical names, date of birth, height, weight, hair color, and DNA--of all things! One of them in question had been serving time in prison while the other was not. The one thing that seperated them was their fingerprints! Needless to say, some fast detective work prevented the detainee from being wrongfully accused of a second crime based on mere discription!
If you are talking about the William West case, I have read that it is considered a myth. However, it has a fantastic point - fingerprinting CAN solve that very problem. Pretty amazing, huh? 
 Ghostwriter :
Very informative newsletter! I've always wondered about fingerprinting and felt dubious whenever an officer took my prints. He'd press down hard on the inkpad and later on the document and I could see blurred ridges of my prints. But I still thought these prints worked anyway.
I'd be interested in reading your next NL about the art of fingerprinting.
How often have your prints been taken?   I hope you found the second installment interesting. Thanks for sharing!
rose_shadow:
What a fascinating newsletter about the history of fingerprinting. Modern day crime detection shows have made the public so used to the idea that we forget that it's a relatively recent science.
It is fairly new, isn't it? Most of the literature I read was concerned with how slowly the science has moved forward. Impatient scientists.
Vivian  :
Thank you for an excellent source of material for mysteries. I'm glad for any information concerning fingerprints, especially since until I read your newsletter I didn't realize how much I needed it. ~~ Viv
That's so nice of you. Yes, I did not realize how much I did not know either. I have been reading up on this for weeks and I still feel like I know only a small percentage of what is going on in this field. It has me hooked, though...I hope to read up more on fingerprinting.
 By the way, I would like to thank The Milkman for switching places with me. I would never have been able to get this newsletter out two weeks ago. Thanks!!! The Milkman !!!!
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