Figure 1
A sheet of glass was used to flatten the cast. The cast was then
photographed with oblique lighting. This is the same cast as shown
in figures 5 and 6. Notice the difference in contrast quality.
Abstract: This report discusses the success that has been achieved by using the Mikrosil casting method in obtaining exemplar prints from cadavers and also its advantages over other traditional methods.
In years past, depending on the degree of friction ridge damage, identifying an extremely burned, decomposed, or mummified body could take several days or even weeks to accomplish, if at all. The condition of the victim’s fingers would not allow for the standard fingerprinting techniques (e.g., ink, photography, or tape-lift methods) to be successfully employed. Usually in these cases, the victim’s fingers or hands would need to be removed from the body and taken to the lab. At the lab, the fingers or palms would be rehydrated by a variety of chemical soaking techniques to return the skin tissue to a pliable, soft condition [1]. After conditioning of the fingers, the ridges would then be recorded using ink, photography, or a fingerprint powder lifting technique. This process was time-consuming, delicate, created a chemical and biological hazard, and mutilated the body.
On occasion, prior to the removal of the fingers or hands, recording of the fingerprint ridges would first be tried by using a black fingerprint powder tape-lifting technique [2]. This was accomplished by placing a layer of black latent fingerprint powder on the victim’s hands or fingers with a fingerprint brush, lifting the impressions with standard latent fingerprint lifting tape, then placing the lift tape containing the fingerprint impression onto a clear sheet of plastic acetate. The clear plastic acetate sheets helped to retain the orientation of the fingerprint impression when the fingerprint was viewed through the plastic acetate side. This would only work on the f lat areas of the fingers or palms. Creased, wrinkled, or shriveled areas of the finger or palm would be difficult to record. As an improvement to the tape-lifting technique, large (8" x 8") white, slightly elastic, adhesive lifters (Kinderprint Handiprint Hand Print System) were used and provided excellent results for several years. However, in cases when the fingers and palms had shriveled and hardened, obtaining a complete major case set of fingerprints was difficult with any of the powder lifting techniques.
Mikrosil has been used for tool mark impressions and molded (plastic) fingerprint impressions for years [3] and it has been used for lifting powdered prints from rough-textured surfaces [4]. Mikrosil has even been used to recover latent prints from dead bodies [5]. According to the developer (Kjell Carlsson), one of Mikrosil’s original purposes was for postmortem applications. He also suggested that oblique lighting would yield greater contrast than using the cast or the cast and powder techniques [6]. In 1983, the use of Mikrosil casting material to cast the fingers of the deceased was described [7], but it has not been commonly implemented.
In one-and-a-half years, this technique has been used to obtain fingerprints on twenty-two decomposing, mummified, or burned bodies. But most importantly, the majority of these victims were able to be identified via the Cal-ID/Automated Fingerprint Identification System (AFIS). This fingerprinting casting technique has saved hundreds of hours over the soaking technique. The ability to immediately identify a previously unidentified body has brought relief to victims’ families and has many times been a major break in an investigation. The ability to identify the bodies translates into a savings of time and money (the necessity of further investigation by a forensic odontologist is avoided).
The author has been able to take the casts directly to the Cal- ID/AFIS Division where the cast was captured directly into the computer using a digital camera. Lately, he was asked by Cal- ID/AFIS Division personnel to stop using the black power and use the casts by themselves. This seems to work better for direct capture into the AFIS.
Because the fingerprint cast is three-dimensional, the Cal-ID/ AFIS Division personnel use oblique lighting on the cast to show the ridges. This has caused some difficulties in getting the light into the deeper section of the cast. A method was devised using a piece of glass to f latten out the cast and to properly deliver the light for an even exposure and optimum results (Figure 1).
A call from the morgue was received concerning the autopsy of a decomposed, mummified body. Knowing that the body was mummified (Figure 2), some Mikrosil casting material was taken for experimental purposes. The victim’s fingers were wrinkled, shriveled, dehydrated, and hardened (Figure 3). To prepare the fingers for the casting techniques, the fingers were cleaned, dried, and a layer of black latent fingerprint powder was applied. As the fingerprint brush was applied, the powder transferred and accumulated onto the ridges. The furrows between the ridges received little, if any, fingerprint powder. Because the palms were still somewhat pliable, the hands were placed palm side up. Paper was rolled and placed between the victim’s fingers to keep them separated (Figure 4). Enough Mikrosil was mixed to cover the surface area of three fingers. (Mikrosil sets up quickly and will harden before a fourth finger can be treated.) The Mikrosil was mixed according to the instructions. (In a case where the palms and fingers are stiff or clenched-up, the fingers or palms can be cut or removed to gain access to the friction ridges. However, most of the time, enough working space can be found.)
It took about fifteen minutes for the casting material to set up. As the cast was peeled off the finger (or palm), the fingerprint powder that had been applied to the fingers stuck to the cast (Figure 5), producing a high-contrast, highly detailed, threedimensional mold of the subject’s finger. The ridges on the cast appeared black and the furrows appeared white. The fingerprint orientation on the cast remains the same as if one were looking at a normal inked fingerprint impression.
The casts containing the fingerprint mold impressions can be photographed or used just as they are (Figure 6). However, it is recommended that photographs of the cast be taken. Each cast should be marked with the case number and with a number corresponding to the finger from which it was made.
In another case, ridge detail was not able to be obtained using the normal cast method. The victim had a skin condition (eczema) that encompassed the entire body. After unsuccessfully using the black fingerprint powder and white casting material, Greenwop (Lightning Powder Company) and black casting material were tried. Greenwop powder was applied on the friction ridges. Black casting material was placed on the fingers. The black casting material was allowed to set up and was removed. Using a black light on the cast, a f luorescing impression of the ridge detail was observed (Figure 7). The black background that the black material provided easily absorbed any visible light from the black light, yielding a highcontrast, high-quality impression of the victim’s fingerprints. These Greenwop f luorescing fingerprint impressions were sufficient for an AFIS search. The impressions were captured using a digital camera. The f luorescing fingerprint impressions were scanned into the Cal-ID/AFIS Division, but unfortunately, the victim’s fingerprints were not on file.
On another occasion, the casting technique was used on a body that had been buried under concrete for almost six years (Figure 8). The casts of the victim’s fingerprints were taken to the Cal-ID/AFIS Division. The database was searched, and a positive identification was established.
Using Mikrosil at the morgue has proven to be a very successful technique. Good results have been obtained from difficult cases. This casting technique has replaced the chemical soaking techniques as a standard procedure. The chemical soaking techniques should be used if casting were ever to fail or when no visible ridge detail can be seen on either the fingers or cast. Even after restoring a finger using a chemical soaking technique, casting would still be a good technique to use to record the impressions. Rehydrated fingers are very damp and slippery. Trying to use an oil-based ink to record a fingerprint impression is difficult and requires several attempts. However, using a cast to record the restored friction ridges will yield better results than will inking alone.
*From the Journal of Forensic Identification Vol. 55, No. 4, July/August 2005
The Official Publication of the International Association for Identification
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