Video Transcript

Bryan T. Johnson, Major Incident Program Manager, Latent Print Unit, FBI Laboratory Division: Welcome to another installment of the Postmortem Fingerprinting video series.

In this video, we will look at the effects of decomposition, when the skin layer starts to break down and separate. This intermittent stage of the decomposition process can be crucial for getting viable fingerprints for identification. 

Other than heavily mummified hands, sloughing hands are the most common cases labeled as unprintable. They are rarely unprintable if the skin is still present on the hands, but trying to print them with ink and paper like a fresh deceased case simply will not work. Understanding the layers of skin, the different options for printing the layers, and the tools that can assist the practitioner to obtain the prints will greatly increase the number of identified cases.

Lastly, we would like to thank the District of Columbia Office of the Chief Medical Examiner for their collaboration and participation in this series, ensuring that everyone watching is provided with the tools needed to identify unknown deceased everywhere.

As always, when addressing postmortem fingerprinting, the first thing to do is to inspect the hands. This first hand exhibits a decent amount of decomposition, with both dehydration and skin slippage. The other hand exhibits obvious signs of mummification; neither the skin nor fingers are pliable or bendable and that is because they are very dehydrated. The size and thickness of the fingers also indicates that the skin is highly mummified. Typically, this drastic difference between the two hands occurs by the positioning of the body after death, wherein the decompositional fluids pool into one hand, causing it to macerate, while the other one mummifies. This is also seen when one hand remains in water while one hand is not, until the body is discovered. It essentially depends on the environmental conditions and geographical locations as how the hands react after death.

For the heavily mummified hand, the best course of action would be to do a sodium hydroxide or ammonium hydroxide soak. This kind of liquid reconditioning can rejuvenate the skin and joints enough to allow for printing or photography. But for the macerated hand, it is best to try and clean it, dry it as much as possible, and then deglove the outside of the skin. Removing the epidermis from the fingertips is one possible way to get a usable fingerprint.

Lastly, the technician should attempt to rehydrate the dermal layer after removing the epidermis by boiling it, making the dermis usable again for a short time. This can be done by boiling the hand in intervals of 15 seconds at a time and then printing. Please see the video specifically dedicated to the boiling method for more details.

In some macerated hands, it may be possible to print the fingers as is without removing the epidermis. That should always be the first step in case the prints captured are of sufficient quality, but as the epidermis on these fingers is starting to slough and the skin is slipping around, it likely won't have enough internal finger structure left to do that. As the tissue and muscles dehydrate, they often shrink in size. The internal finger structure is necessary to allow the friction bridges to remain three dimensional and be printed.

In order to do the least amount of work per case, the first thing should always be to clean the hand and fingers as best as possible. This can be done with soapy water and a gentle sponge, or just rubbing alcohol or acetone. After cleaning off the end joint to the fingers thoroughly with a towel, rubbing alcohol or acetone will also expedite the drying process. This allows the hand to be printed or rehydrated more efficiently. Any kind of dirt, fluid, or other residue left on the friction bridge skin will inhibit the ability to obtain proper quality prints, so it is very important that this step is done meticulously. A final wipe with a clean dry towel or a tissue can ensure that any remaining particles are removed so that the fingers can be printed.

After the skin is clean and dry, one of the fingers should be printed to determine the quality of the print that the skin will produce without any additional rehydration methods. In this case, the thumb is rolled with ink and then rolled again onto a white printing strip. The resulting print should be representative of the expected quality of the rest of the fingers on that hand with no further processing.

As suspected, the recorded thumbprint is very low quality, not likely identifiable. Even though visibly the ridges are there and could possibly be photographed, the skin is not sufficient for recording at this point. As stated previously, the skin structure must be intact enough to be able to support the ridges and obtain a good quality print.

Since it has already been determined that there is skin slippage, the next step is to excise the epidermal skin. It is crucial that no incisions or injections are ever made directly into the skin pad of the end joint of the finger. To excise the outer skin layer, a gentle incision is made on the outsides of the friction ridge skin on sides of the finger. Care must be taken to remove the skin without damaging it or the dermal skin layer underneath. General safety must also be a constant consideration whenever utilizing scalpels or other sharp tools in close proximity to the technician's hands.

Once the sides of the skin are cut, iris or curved scissors can assist the rest of the task to neatly and gently finish removing the skin. Simply tearing or pulling off the skin can lead to damaging the end joint of the skin and ruin any chance of getting a full quality recording. The skin can then be gently pulled up, being careful not to tear it.

The fingernail will oftentimes come off with the outer skin, which does not create any issues. It may also completely separate after detaching the epidermis, and care should be taken to ensure it remains with the deceased. If it is attached to the degloved skin, the technician may either leave it on, or for ease of wearing the skin for printing purposes, it can be carefully removed as long as it stays with the remains.

Once the skin is removed, it should be examined and further cleaned. Note that the epidermis still has a curved structure. The skin in this case is still very wet on the inside, as is the dermis. Even though it was clean and properly dried, the decompositional fluid will be trapped between the skin layers. The dermis will also be overly moist and must be cleaned as well if it is to be printed. Much like the original attempts, alcohol or acetone will help in cleaning and drying their removed epidermis as well as the newly exposed dermis to make it usable for printing. Please note, anytime skin or digits are removed from the deceased, extra care should be taken to ensure they are not mixed up or lost.

Looking at the exposed dermal layer of the finger. It is important to ensure it is dried off. The finger will usually appear to be a different color and much smoother than the epidermis. Upon visual observation, the dermal fingerprint ridges are still there; however, they are extremely fine and more delicate. It is very improbable that the dermal skin will be able to be printed without additional rehydration, but it may be worth trying. For dermal skin, it is highly recommended to use black powder and adhesive lifters, as there isn't enough resolution in standard ink and paper recordings for the fine dermal ridges to usually be captured. A thin layer of black powder is applied to the finger, ensuring not to saturate or cake the powder on the skin. The powder also acts as a bit of a desiccant and helps to dry out the finger.

After examining the lifted print, it can be seen that there is very little usable ridge detail here, as expected. The dermal ridge structure has dehydrated and deflated to the point where the dermal skin on the finger is not usable without additional rehydration methods, such as the boiling technique. Continuing in the process, the previously detached epidermis should be printed next. Utilizing an alcohol wipe or acetone to clean and dry out the decomposition of fluid on both the inside and outside of the epidermal skin, the skin will now be ready to be printed.

Once the alcohol dries, it can be placed over the practitioner's gloved hand, which gives it the structure it needs to be recorded properly. It should be gently smoothed out until it contours to the gloved finger. Care should be taken not to tear the skin across the friction ridge pattern area. Due to dehydration from the decomposition process, the fingers actually reduce in size, and that is what allows the separation of the epidermis from the dermal layer. This natural process of the skin deteriorating also diminishes the structural systems of the ridges that allow them to be printed. By placing the skin on a gloved rigid finger, it more resembles what would've been the antemortem finger in size and shape. When using the degloving method, it is important that the practitioner has similar or smaller sized hands in the deceased. When the skin is removed without being cut down the sides, it will inevitably tear when attempting to wear it on the gloved finger.

After cleaning and drying the skin, it is now ready to be printed. A thin layer of fingerprint powder is applied to the skin using a foam or stiff bristled brush. The degloved skin can then be rolled as though the practitioner was printing themselves onto a vinyl lifter. It is important to make sure the skin does not stick to the lifter and tear, if at all possible, as it is removed. After gently peeling the skin off the lifter, the lift can be placed on the back of a clear acetate for preservation and the skin placed back with the body or on a numbered sheet for tracking purposes.

Examining the adhesive lift of the epidermal skin, an increase of quality is seen, but not enough to be considered a good quality print. The next step in the process is to try and print the inside of the epidermis by turning it inside out. The same pattern and lifter technique is used for this step as well. One point to note about this process is that any lift taken from the inside of the epidermal skin will be backwards, known as reverse position, so it is important to note that on the fingerprint card before submitting it.

While there is some ridge detail observed, the lift seems a little bit light in contrast. Additional powder is added to attempt to increase the darkness of the print. If too much powder had been applied, simply taking an additional lift without reapplying is often all that is needed.

The new lift is added to the acetate sheet, noting that all of the recordings thus far are from the same finger. The top is a recording of the dermal layer, where there is no ridge detail present; next, a recording of the epidermis, which is pretty well decomposed and not a lot of great ridge detail; a recording of the underside of the epidermis, with not enough powder on it; and finally, another print of the inside of the epidermis, which is a little better, but still poor ridge detail.

Still, not having a good quality print from this hand, the next logical process to rehydrate the fingers would be to use the boiling technique. The boiling technique will be explored in a different video to fully explain how it works. In order to do the boiling technique, the dermis must be exposed.

The next finger's epidermis is removed whole by using scissors to cut the skin below the joint all the way around. It is then slowly pulled and slid upwards off the finger. This finger still has a little patch of attachment between the skin layers that must be gently separated. The use of a dental pick can come in handy here when a small portion of the epidermis is still attached to the dermis. The pointed part of the pick is not used, but rather the metal bar can be used to scrape sideways to slide between the layers and separate them. It is important not to use a scalpel for this step, as it would inevitably cut the ridges on one of the principal skin surfaces and damage them beyond use.

After removing it, there is a little bit of tearing seen on the degloved skin from turning it inside out. This means that during the printing step, extra caution will need to be taken to ensure it doesn't tear more. This is an example, though, of wearing it whole to give it its full dimensionality back and its full texture. The whole glove of skin can then be slid carefully onto the practitioner's finger. As discussed before, it is typically easier just to cut down the sides rather than remove the whole section, because then there are no concerns about tearing, pulling, or size of the finger as it is worn.

At this point, the ridges are visible, so an intermediate step could be to photograph the skin with a ruler and a macro lens. This can also be done at the end of the process with all of the removed skin or rehydrated dermal fingers. Photographs, however, cannot be easily run in automated fingerprint databases, so they should not be the first method attempted or relied upon.

As before, the skin is cleaned and dried with an alcohol wipe and then gently blotted onto a towel to remove any residual particles or liquids. Again, the finger would best be printed with powder or lifters due to its low quality, but to demonstrate the difference in quality between the techniques, ink and paper will be used to print this finger. The skin is first rolled nail to nail in ink, and then again, nail to nail on a paper strip to record the fingerprint. The prints recorded in ink look decent from afar, but it still does not have the quality needed to effect identification. This is due to the level of decomposition of the epidermis.

To show contrast, the same finger will be printed using powder and an adhesive lifter. There is much cleaner and finer rich detail in the powder lift than the ink lift. This photo shows the drastic difference just by using a different recording technique after the boiling technique was performed. The ink print was quickly rejected, whereas the powder print was easily identified.

When excising or degloving multiple fingers, either for printing or to prepare for boiling, it is important to track which finger each portion came from. In this demonstration, only the number three and number four finger epidermal layers were removed. By using something as simple as a numbered paper towel or labeled jars, the skin or fingers can stay cataloged in case they need to be reprinted. For this case, only a couple of fingers were demonstrated. In most cases, the focus would be on the thumb and indexes first due to their higher likelihood of being identified, but all of the fingers should be processed. When finished, all detached portions respectfully need to remain with a decedent in the body bag.

Degloving is encountered on a daily basis in most morgues, but it is often a cause for those without proper training to avoid attempting to capture postmortem prints. The alternatives of using DNA or dental comparisons typically requires having a tentative identification to the decedent. Through a little extra hard work and dedication, each case can affordably and effectively be fingerprinted, likely leading to an identification. With three different possibilities to print the deceased, using both sides of the epidermis and the dermal layer, there is always a good chance to be able to get a set of usable prints.

We encourage you to watch the remaining videos in the series so that you may learn additional rehydration and reconditioning techniques that can further assist in obtaining the prints needed to identify the deceased. We also encourage you to reach out to the FBI Laboratory with any questions you may have regarding this content or any case-related questions we may assist you with.