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In the winter of 2011 a corpse of a teenager was found in a fallow field after three month of environmental exposure. The autopsy showed no sign of rape but the presence of several cuts on the victim’s body. Despite exposure to weathering and animals, the clothes from the waist up were well preserved, whereas the trousers were extensively torn and the underpants were clearly cut.
Searching evidence from the perpetrator was difficult since the traces present on the victim’s clothes and underpants were subjected to morphological and chromatic modifications due to the environmental exposure. Initially, sample collection was based on an integrated approach that involved circumstantial information and inspection with the forensic light. The use of this light source allowed us to identify some areas with more clearly fluorescence, also visible to the naked eye, that were the first to be collected. The accurate inspection led us to perform approximately 300 samplings on the clothes. In one of these areas (called 31-2) located on the underpants, the results of the sampling showed the presence of alleles unrelated to the victim. As a result, an extensive sampling through the application of a virtual grid was undertaken in this area to confirm and improve the male profile and obtain serological information. Due to the complete absence of other relevant clues on the perpetrator, when a full male profile -Unknown Male #1 (UM#1)- was found on the victim’s clothes, a huge mass screening that involved the collection and analysis of over 16,000 reference samples was carried out, until a full match was obtain.
On February 2011, in a fallow field a teenager’s body was found completely dressed in a jacket, a hooded sweatshirt, a shirt, a bra, trousers, underpants, socks and shoes. Despite three months of exposure to weathering - rain and snowfall - and animals, the jacket and hooded sweatshirt were well preserved, whereas the trousers were extensively torn and the underpants were clearly cut. The autopsy showed no signs of rape but the presence of several cuts on the teenager’s body. All clothes were sent to the forensic genetics department of Carabinieri in Parma in an attempt to extrapolate any useful information in absence of other important investigative elements. To explore the presence of biological fluids on the clothes, the visible characteristics of the samples were accurately examined and described with the naked eye and a thorough examination of the fabrics and lacerations present was carried out with the help of product experts. Then, the evidence visualization was enhanced by light-interaction techniques. The careful inspection led us to perform approximately 300 samplings on all the clothes. Due to the fact that the most significant traces were found on the underpants, here, we focused our discussion on them.
2. Material and methods
Since the physical contours of the biological traces appeared unclear, presumably due to the weathering and the diffusion of cadaveric liquids degradation, the collection strategy on underpants was developed in three phases. The first one was performed by cutting the underpants areas that showed positive light interaction results. Subsequently, the second phase was based on the results of the first one, by applying a virtual grid (Fig. 1) to collect samples around the areas that showed alleles different from the victim.
Fig. 1Application of a virtual grid on underpants. Each portion of the grid was a sample. The sample 31-2 was originally taken from the area inside the grid without fabric.
At the same time, the third phase was focused on obtaining information on biological fluid that constitutes the UM#1 trace with the use of different presumptive and confirmatory tests [
S.C. Ebach, F. Ramsthaler, C.G. Birngruber, M.A. Verhoff, Determining the postmortem interval of bone samples: a comparison of luminol chemiluminescence, Hexagon OBTI test, and Combur test, Arch. Für Kriminologie. 226 38–47.
]. At the end of the collection activity 52 fabric fragments, just over 1 cm2 in size, were cut from the underpants. For a more accurate serological sperm research we used fluorescence microscopy using a kit called Sperm Hy Liter – Indipendent Forensics – able to detect the presence of a single spermatic head in a sample [
The analysis of the first area collected by underpants (named 31-2) showed the presence of a mixture profile composed by the victim’s STR profile and a male partial profile. Due to the limited number of alleles and the high level of uncertainty that characterized the allelic call, this male profile was useless for database comparison. In order to try to obtain the full male profile, the subsequent sampling was carried out around the 31-2 area. Due to the fact that the laboratory activities were focused on obtaining serological and genetic information, some of the areas collected were divided into two: a fragment for serological analysis and the second one for DNA fingerprinting to confirm the presence of the same male profile and to exclude other contributors.
One of these areas, named 31G20, showed a single full male profile (UM#1). The 31G20 area was tested for the presence of saliva, sperm and blood. Negative results were obtained for saliva and semen, whereas positive results were obtained for blood.
4. Discussion
Due to the modifications related to biotic and abiotic factors, having to deal with a body exposed to environmental modification for three months can be challenging. The biological traces can appear unclear, probably due to the weathering and the diffusion of cadaveric liquids, and the inspection with naked eye/light-interaction techniques can give little or no support. The positive light interaction results that were used as a first criteria to sample specific areas allowed us to collect an area with low male DNA (sample 31-2, 0.002 ng/μl). The sample that showed the major concentration of male DNA was 31G20 (1400 ng/μl) sampled in an area around the first one in which a male DNA was isolated on underpants (31-2), using a virtual grid. In this casework, the application of a grid allowed to have information of the mixture ratio between the victim and the suspect and to delimit one area with the presence of DNA from UM#1. We considered this area as a great one trace. Thanks to an adequate amount of DNA, the analysis with different STR kits was possible to carry out. This approach was performed for two main reasons: 1. confirm the result obtained by each marker because different kits use different primers to amplify the same marker; 2. increase the number of markers in order to obtain a more discriminative LR for familial relationships [
Due to the fact that this male profile was never found before in the database of our laboratory, the prosecutor decided to find the suspect via a huge mass screening. The male STR profile was compared with about 16,000 samples taken from citizens related to the area of the discovery of the corpse (for example with cells tower or city of residence). As a result of the massive investigation and mass screening activity, three years after the STR typing of the UM#1, a match with a reference sample was found.
5. Conclusions
In this casework, awarded as “DNA Hit of the Year 2017″ [
], the use of the most innovative forensic genetics techniques, associated with a grid collection approach and a mass screening flanked by a familial searching, has made it possible to bring “an above suspicion man” to justice, even in the absence of other valuable clues.
Declaration of Competing Interest
The authors have declared no conflict of interest.
Acknowledgements
We would like to express our gratitude to Biology Section of RIS Carabinieri in Parma and all the people involved in this casework for their valuable investigation activity.
References
Immunochromatographic Rapid Test for the Detection of Fecal Occult Blood, Max-Planck-Ring 21, D-65205.
S.C. Ebach, F. Ramsthaler, C.G. Birngruber, M.A. Verhoff, Determining the postmortem interval of bone samples: a comparison of luminol chemiluminescence, Hexagon OBTI test, and Combur test, Arch. Für Kriminologie. 226 38–47.
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