Fingerprints are considered to be a key role and the most valued tool in crime scene investigation. The detection of latent fingerprints is practically a challenging analytical problem, where detection of very small quantities of specific chemical compounds is required (Cadd et al. 2015). Consequently, the current study was conducted to evaluate the possibility of recovery of submerged latent fingerprints on non-porous surfaces using different techniques. Black powder, SPR and CA were used in the current study as these methods are the most commonly used techniques and they are fairly adaptable in their applicability (Yamashita and French 2011).
The groomed fingerprints were used in the current study. Although International Fingerprint Research Group (IFRG) stated that natural fingerprints is preferable, but groomed fingerprints were accepted in cold weather (18 °C) (Almog et al. 2014).
Home- made cyanoacrylate fuming chamber was used as it’s cheap, easy and could be made from available items. Different agencies and institutions especially in developing countries cannot afford the acquisition of fuming cabinet with programmable humidity. In the current study; all surfaces subjected to cyanoacrylate fuming were placed under the same experimental conditions (temperature, humidity and time).
In order to assess the effect of water salinity (fresh versus sea water) on latent prints development and the effect of various methods on the same substrate, it was better to leave the surface two hours to dry before applying SPR. This is to exclude effect of surface wetness during the comparison of black powder, SPR and CA.
The present study revealed that; successful recovery of good and very good quality of latent fingerprints is possible following submersion in different aquatic environments. In crime scenes, it’s unlikely that fingerprint processing and enhancement takes place immediately after deposition especially in underwater crime scene (Soltyszewski et al. 2007). Therefore, fingerprints were examined at different intervals; 1, 2 and 10 days.
In the present work, either in sea or fresh water, the duration of submersion in water has its effects with a marked diminished quality of fingerprints in longer duration (10 days). However, prints of good visibility (score 4) were still detected at 10th days when CA fuming was used. This could be of practical importance during examination of such evidences whatever the nature of the surfaces.
The reduced quality of developed fingerprints with increasing the time elapsed since deposition may be explained in the light of the fact that; fingerprint composition changes through various chemical, biological and physical processes resulting in the aged composition (Cadd et al. 2015). Initial compounds are lost through various processes including degradation, metabolism, migration, oxidation and polymerization. The longer aging periods may result in greater degradation of fingerprint components (Girod et al. 2012).
Former research exploring these changes has chiefly focused on lipid components; fatty acids, wax, esters, triglycerides, cholesterol and squalene within fingerprints, as these tend to decrease significantly in concentration over time (Mong et al. 1999; Weyermann et al. 2011). Additionally, water, bottom mud, sands and other factors can very easily cause prints to fade faster. Trapecar study (Trapecar 2012a) demonstrated similar results in his study made on wet foil, where he assumed that the quality of the developed fingerprints on objects found in water would depend on the length of submersion.
Similarly, Soltyszewski et al. (Soltyszewski et al. 2007) confirmed the possibility of recovering fingerprints deposited on glass slides submerged in river, sea, tap, or distilled water. However they used; aluminum powder, ferromagnetic powder, and CA. They found a decrease in latent fingerprint visualization with increasing the duration of submersion. In contrast to the results of the present study, they stated that prints submerged for 1 and 7 days were on average of good to very good visibility in all used techniques at 5 °C. This may be referred to the difference in methods of visualization, temperature of water between the two studies and the effect of sand and mud on reduced quality of visualization.
The present study also demonstrated that, the highest percentage of good and very good quality (score 4, 5) of fingerprints was detected when CA technique is used.
Additionally, in comparing the three studied methods, a significant difference (p ≤ 0.05) was demonstrated among them in most of the examined prints.
Similar results were obtained in another study by Trapecar (Trapecar 2012b), where the examined glass and metal surfaces were exposed to the influences of stagnant water during different time intervals. He concluded that, the best results were achieved with CA. Although, silver special powder, SPR (black and white) and CA were used for prints development. Moreover, the time intervals were; 4 h, 1, 2 and 7 days.
In contrast, Trapecar (Trapecar 2012a), showed that SPR is the best method for development of fingerprints from wet transparent foil surface submerged in stagnant water during different time intervals. It could be attributed to the different nature of the surface used and to enhancement technique being applied while the surface is still wet, while in the current study various techniques were used after the surfaces being dried.
A study investigated the effect of aquatic environment, as a destructive crime scene condition, on the quality of fingerprints. Water has an effect on the survivability of latent prints, and their successful development (Dhall and Kapoor 2016). Sea water had more destructive effect due to its salinity; this could be explained by the good quality of fingerprints recovered from fresh water versus sea water as revealed in the current study.