Tissue Builder Technique

In-depth coverage of how to inject fluid under dehydrated finger pads to rehydrate the skin and then capture the prints.


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 look at the use of Tissue Builder to rehydrate dehydrated fingers. Tissue Builder or other viscous liquids can be a fast and easy way to get a finger back to the antemortem condition. By simply adding fluid back under the surface of the dehydrated finger, the decedent can be quickly printed using traditional means. Hopefully after watching this video, you will be more knowledgeable about the rehydration of the skin through injections and have another tool in the toolbox for identifying the deceased.

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.

The first step in any case is always to inspect the hands. Start by checking for signs of rigor mortis or any trauma. Check to see if the hands bend and the fingers move. The easiest way to do this is to bend them back and gently stretch them out so that each of them becomes pliable. After the fingers are movable again so they can't be fingerprinted, the next step is to assess the condition of the skin.

The hands in this case are dry and there is very little moisture or oils exuding from them. There appears to be a little bit of skin slippage happening on some of the fingers, but overall the condition of the hands is good. It is important to note that there is some desiccation of the hands or the early stages of mummification. The skin also appears pruned, a common side effect from both peri mortem and postmortem dehydration.

After the initial analysis, the first step towards taking prints is always to clean the fingers and hands thoroughly. Soapy water with a gentle sponge or alcohol wipes will usually be sufficient for this task. Really oily hands can be cleaned with acetone. Caution should be taken not to damage the skin or to cause any unnecessary sloughing of the epidermis, which is the outer layer of skin.

For identification purposes, the most important part of the hand to be concerned with is the end joint of each of the fingers. That is the first finger crease up to the tip of the finger, where the fingernail ends. In some types of major crime or high-profile cases, there's need to do full palm prints or major case prints. That process will be shown in a separate video. For this video, only the last joint of the finger will be discussed because that's typically the identifiable print that will correspond to an antemortem fingerprint card on file.

Once the hands have been cleaned, they can be reconditioned. For this hand specifically, there is a decent amount of wrinkling observed. The first step is to try and tighten the skin by pulling back on it in a pinching motion to see if it regains its original shape. This is very functional for most cases to get the wrinkles out of the skin. It works like a finger facelift and keeps it taut so that it is flat. Each of the reconditioning techniques are to try and make the finger appear the same condition that the person was in before death so that their fingerprints will match the card on file. By bending it back to make it taut or pulling it from the side, it is easy to see which works best. For hands that are more difficult, you can inject a chemical called Tissue Builder or any other viscous fluid that will help you keep it nice and taut.

To do that, Tissue Builder is drawn into a syringe and then injected into different parts of the finger. The goal of this technique is to give some of the turgidity back to the fingers. In this case, it helps alleviate the wrinkles permanently. It is very important never to compromise the end joint of the finger by perforating it. It is also important to try not to insert it at an extreme angle because that will likely perforate the skin as well. Any damage or holes put into the end joint of the finger can damage minutia or render the print unusable. It is best to come in from a flat angle, always below the joint crease, or from the top or extreme sides.

The needle is gently inserted between the bone and the volar pad, taking care not to puncture the surface. The fluid is injected slowly and then carefully massaged into place. It is important not to over inject because it can distort the final print. Tissue Builder will harden into a gel upon impact. The difference in the finger is easily observed now that it has Tissue Builder in it. The Tissue Builder will continue to solidify now that it doesn't leak back out like other liquids would. Other viscous liquids such as alcohol, acetone, or any other non-volatile substance can be used, but care should be taken because wherever the perforations are, the liquid will come back out. This will be especially noticeable when applying pressure to print the finger.

At this point, the thumb is now sufficiently rehydrated and reconditioned. There are still a few wrinkles present, but that's not an issue because when the finger is pressed against a print medium, it will flatten the rest of the way out and leave a nice flat print. Similarly, if the skin can be held back and taut on its own, the wrinkles will actually squish out when printed. The assistance of a second practitioner may be advisable if not using the injection method to keep the skin firm while printing. The key here is not to allow any major wrinkles in the recording. Wrinkles are important to keep out of the fingerprint recording because if the skin folds over on itself and isn't recorded, it distorts the information needed for an automated database search. It can also change the spatial relationship of the information contained in a fingerprint, which can further inhibit successful searches for an unknown person.

The rest of the fingers can be quickly injected as well to help them rehydrate to their natural shape. As was previously stated, it is also important not to inject too much solution because it will cause the skin to stretch out unnaturally. This will cause the shape and size of the finger to deform. The finger should appear natural in relation to the hand and the size of the decedent. Again, the insertion should be mostly parallel to the finger—that way, when it goes in, it goes into the skin between the volar pad and the bone. If the needle hits the bone, back it out partially and try again. If only part of the finger is rehydrating due to partial mummification, it may be necessary to inject from multiple sites to get the whole finger done. It is never acceptable to inject through the friction ridge arrangement.

Injecting fluid under the skin is a quick and reliable method of preparing the hand for printing. The supplies needed can be found in almost all morgues, and after a little practice, it is a fast and easy way to get the fingers back to printable shape.

We encourage you to watch the remaining videos in this series so that you may learn other 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.