Sirchie makes hundreds of products for the law enforcement community and offers classes in how to use those products at their Youngsville, North Carolina Education and Training site. Several crime writers were allowed an unprecedented opportunity to attend a five-day, hands-on training session, so that we could learn more about the latest and best gadgets being used to catch the crooks.
Included was incredibly valuable information about fingerprinting. Robert Skiff (Training Manager/Technical Training Specialist at Sirchie) put us right to work, using the powders and brushes needed to process a crime scene and used by actual techs in the lab.
Fingerprint powders, brushes and magnifier
There is no such thing as a perfect crime, but the jails are filled with crooks that swear they have been framed. Common excuses: “I was at my girlfriend’s house at the time of the crime,” “Somebody planted that shoe print,” etc. It’s up to the investigators and examiners to prove the case against the suspects, using proper evidence collection techniques and tools, because trace evidence is ALWAYS left behind by even the most careful criminal.
Fingerprints found at the scene are still the favored piece of evidence tying the suspect to the crime. These days, using a combination of ingenuity and newly developed chemicals and powders, a crime scene investigator can lift (and/or photograph) prints from many previously challenging surfaces.
About a month before the session started, we got a letter in the mail telling us NOT to wear good clothes to class. Hmmm… My thought was that we were going to be doing some messy evidence collections outdoors or in the mud, etc. Nope. Black fingerprint powder gets all over everything when newbies are handling it for the first time. We must have used 50 wet wipes each during the morning alone.
After dusting prints with black fingerprint powder,
they were lifted from various smooth surfaces using (in forefront) a gel lifter, a hinge lifter and (in background) tape.
We had to be careful not to contaminate the powders and jars or smear the samples themselves before looking at the prints under the magnifier. By the end of the day, most of us had black eyes and streaks on our hands and faces. It looks much easier on TV.
Our prints were photographed and then viewed under an Optical Comparator. This machine can be hooked up to a laptop, and the image sent off to AFIS for identification purposes. No crooks in our crowd, so we omitted that step.
At the end of the first day we left happy, tired, and still wiping powder off our hands and faces. A tip from an investigator taking the class with us: add a cup of vinegar to the wash load to get those powder stains out.
Day One take aways?
*Not all powders can be used on all surfaces.
*A print can dissipate over time and there are too many variables (temperature, humidity, condition of the surface, etc.) to predict how long that might take.
*A really crisp print can be photographed right at the scene, using some great digital cameras now available.
*Forensic science is not a certainty, even though TV shows may give that impression.
*There is no nationwide standard for number of points of ID for a fingerprint. The fact that the acceptable number of matching points (between the actual print and the print in the AFIS database) can range from 5 to 20 depending on where the perp lives, blew us away.
Day Two: Coffee ready. Snacks ready. Notebooks, cameras, smartphones, and pencils ready. Checking for leftover fingerprint powder on the magnifier. Ready.
Robert Skiff’s assistant for the class, Chrissy Hunter, passed out stainless steel rectangles and we pressed our fingers onto the plates, twice. First time - plain ole print, second time - ‘enhanced’ by first rubbing our fingers on our necks and foreheads to increase the amount of oils in the print. The ridge detail in the prints was so clear in the ‘enhanced’
version that there was no need to process them with powder. We lifted them with a gel lift.
If we were working a real scene, that might never happen, but it could. The usual occurrence is that partial prints are left at the scene and that’s what makes the search for the perps sooooo much tougher than what the TV dramas indicate. There is no instant ‘a-ha’ moment that comes 45 minutes after the crime has been committed.
The prints are generally sent off to be compared with the millions in the AFIS database, and here’s where TV parts with reality again. AFIS comes back with a list of 10-20 possible matches and someone then makes a comparison by hand of the most likely hits.
After practicing the basics, it was time to move on to fingerprint discovery on documents. Documents? Yup. There are scheming relatives who forge wills, less than loving spouses who murder for the insurance, bogus suicide notes, and the list goes on. How to prove the nefarious intent? Fingerprints. But…as we discovered the first day, fingerprint powder is messy and almost impossible to clean up. An important document could be destroyed in the search for evidence of foul play. Enter chemicals and alternate light sources (ALS).
There is a protocol for testing with chemicals. If the prints don’t show up with one chemical, then it is possible to try several others, but this can only be done in a certain order:
Iodine
DFO
Ninhydrin
Silver Nitrate
MBD
If used in this order, the sample won’t be compromised, even though treated several times over several days.
We experimented with several chemicals with excellent results, but for the ‘wow’ factor, I’m showing the ones that look great on camera. ;-)
DFO reacts to amino acids in the prints. We created our samples placing our own enhanced prints on plain white paper. We hung the papers in the fume hood, saturated them with DFO, then put them in the oven to bake for several minutes.
This DFO sprayed, baked sample doesn’t look like much, so it was time to use an ALS to really ‘pop’ the print and make it photo ready.
Alternate Light Sources vary depending on the scene lighting and/or need to highlight the evidence. A few used in the field are: the ‘poor man’s ultimate light source’ (a mag light), black lights, UVC lights, lasers, LED lights, Ruvis lights (cost about $20K), and pure white lights. Each has a specific quality that the investigators can tap when needed.
After we sprayed our samples with DFO and baked them in the oven, we darkened the room, and put on orange plastic glasses. Then we side-lit the sample with a 455nm light. The photo was taken at that point.
Same sample, side-lit at a slightly different angle. Photo taken through an orange filter.
Ninhydrin, the third chemical group in the list to be used if nothing has shown up yet, comes in several forms: acetone, zylene and Noveck. Ninhydrin reacts to another set of amino acids and likes warm, moist air. If a sample is being saved overnight for processing, you can place it in a ziplock bag, blow into it, then seal it and still maintain its integrity.
Before working with any chemical, it’s a good idea to make copies of the document. Why are there different kinds of Ninhydrin? Zylene will run some inks. Acetone will run all inks, all the time. Ooops! There goes the document if you grab the wrong chemical, so copies are definitely necessary. Noveck is the clear winner when working with inks. It gets fast results and dries quickly. Additionally, it can be sprayed on an outer envelope to reveal what’s inside. Without damaging either piece of paper. Very cool.
You could see the plots developing in our writerly heads as the Noveck dried and the words inside the folder faded from view.
*Photos taken by Patti Phillips at the Sirchie Education & Training site in Youngsville, NC.
Patti Phillips writes Detective Kerrian’s blog at www.kerriansnotebook.com and the book review site www.nightstandbookreviews.com
