Solving underwater crimes: Development of latent prints made on submerged objects
Introduction
Currently, fingermarks continue to be one of the most interesting types of evidence for criminal investigation. As a result of advances made in instrumental analysis techniques, much more information is provided than that which used to be gathered from their dactyloscopic study. For example, they are a possible source of DNA (nuclear and mitochondrial) [1], [2] and it is also possible to detect and analyze exogenous material which the donor of the print has been in contact with. Remains of explosives, drugs and any substance that has been retained can be gathered and examined in order to determine what is referred to as the chemical print, providing quite useful data for the investigation [3], [4], [5].
Moreover, the chemical study of fingermarks is of interest for understanding variability in the different components between individuals [6]. This information allows an evaluation based on the study of the type and proportion of the lipids that make up the print, whether its author is a child or an adult [7]. Likewise, data can sometimes be obtained on an illness the donor may be suffering from or even on his/her diet [8]. More recently, research was published on the possibility of evaluating the age of the print, focusing on the loss of electrostatic charge that occurs over time [9], or by means of non-invasive optic procedures [10], [11].
The potential of fingermarks as sources of information in criminal investigations justifies the continuous search for new reagents that are suited to the characteristics of the surfaces on which the work is to be undertaken. Consequently, interesting studies have been published that describe, for example, how to reveal marks on especially difficult surfaces, such as human skin [12], [13], or the possibility of obtaining them from paper, even if, after being formed, they have come into contact with water [14], [15], [16]. Indeed, results have been achieved even following the effects of fire [17], [18].
In order to fully take advantage of these products, work procedures have been elaborated that describe, for each type of substrate and depending on the conditions where they are found, an ordered application sequence for reagents, so that each step depends on the results obtained in the previous one [19], [20]. Taking into account the procedures proposed by the manual, one of the most effective reagents for the treatment of surfaces that have been wet is the small particle reagent. This reagent has been used to reveal marks deposited on objects that have remained under water. Different investigations have been carried out, producing marks on different types of surfaces and later submerging them in water in order to evaluate the effectiveness of the reagents under these circumstances. However, the protocols recommend their use as a last choice option due to their damaging effect on DNA [19], [20], [21], [22], [23].
Nevertheless, no reference has been found to the possibility of developing marks that were made under water, or, in other words, obtaining marks deposited on a submerged object.
The aim of this study is to investigate this type of evidence in underwater crime scenes. We can imagine, for example, a fight between scuba divers, a hit-and-run accident at sea, the investigation of a submerged vehicle, or the remains of an explosive device that was placed on the bottom of a boat [24]. The following study is dedicated to evaluating the efficacy of different reagents in developing marks produced under water. Assuming that due to their chemical nature the fingermarks elements that will best resist the effect of submersion are fats, in addition to the small particle reagent recommended by the bibliography, we will use another specific reagent to develop them – Sudan Black – which has shown its efficacy for developing finger and lip marks [25], [26] without causing any negative effects on possible DNA analysis [27].
Section snippets
Methods
Marks were obtained from volunteers who had been asked not to wash their hands for 3 h before depositing their fingermarks, and to avoid touching their faces and heads.
Glass slides (standard, pre-cleaned, without any special treatment, approx. 76 × 26 mm. SUMILAB Ref P02676E) and transparent plastic cards (made from standard photocopy transparency sheets APLI Ref 00860 and cut into rectangles of approximately 76 × 26 mm) were washed with standard soap and water in order to eliminate any type of prior
Results and discussion
The study has tried to reproduce the conditions in which the fingermarks would be produced in real cases. A priori, therefore, different initial qualities of evidence would be expected which, no doubt, would influence the possibility of their development.
The results are summarized in Table 2, Table 3. Table 4, Table 5 show the results for control samples (C1 and C2).
Data included in the summary tables represent the results obtained on at least 80% of the samples developed, i.e. at least 16 of
Conclusions
The aim of this work was to evaluate the possibility of developing marks that were made under water. It can, therefore, be concluded that this aim has been achieved, showing that, even under conditions as adverse as the ones reproduced in the present study, it is possible to develop fingermarks. Likewise, we have been able to determine that reagents are – under the experimental conditions described – more effective for this type of sample.
From this preliminary study, we can deduce the need to
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Small particle reagent based on crystal violet dye for developing latent fingerprints on non-porous wet surfaces
2015, Egyptian Journal of Forensic SciencesCitation Excerpt :The test solution remained stable for about 50 days. To determine the quality level of fingerprint development a Fingermark Quality Scale assessment7 was used (Table 1). Small particle reagent technique has proved its worth in detecting fingerprints on moist, non-porous smooth surfaces.