Developing Methods to Improve the Quality and Efficiency of Latent Fingermark Development by Superglue Fuming

The completed research program was designed to provide fundamental information that can be used to improve the superglue fuming method of developing latent fingermarks, by optimizing the acquisition of developed latent fingermarks and enhancing the quality of aged fingermarks. This has been realized by, first, using our expertise in polymer chemistry to explain the role of temperature on the superglue fuming of aged fingermarks and developing protocols to implement temperature control in a forensic laboratory. Our results show that fuming at lower temperatures improves the rate of polymerization that occurs during superglue fuming and thus, provides an easy and cost-effective method to improve the quality of aged prints developed by superglue fuming. More precisely the results of this project indicate that the optimum temperature of fuming is between 10 and 15 °C. Furthermore, any protocols that are devised to control the temperature of fuming must take into account the presence of the warm superglue fumes. The decrease in temperature also appears to improve the quality of aged latent prints. Previous results also suggest that rehydration of an aged fingermark is critical to its successful development by superglue fuming, and thus we have investigated aggressive rehydration methods of aged latent fingermarks as a method to improve the quality of aged prints. Unfortunately, simply rehydrating fresh or aged prints by exposure to room temperature or boiling water vapor is not a sufficient method for improving print quality. In fact, exposure to boiling water vapor harms prints, presumably by removing initiators by dissolving them into the steam and releasing them from the print before fuming. Finally, we have completed Fourier Transform Infrared spectroscopy (FT-IR) experiments to monitor the molecular level changes during the polymerization of ethyl cyanoacrylate and the hardening process that occurs after polymerization, to provide guidelines that can be used to improve the turn-around time of obtaining a print that can be recorded and compared to a database. Thus, we have completed a series of experiments that provide fundamental information that forensic scientists in the field can use to create protocols to improve the effectiveness and optimize the process of the superglue fuming method to develop, visualize and analyze latent fingermarks. This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 3 TABLE OF CONTENTS Executive Summary 3 Introduction 10 Methods 10 Results 14 Conclusions 21 References 22 Dissemination of Research Results 22 Executive Summary: The cyanoacrylate fuming method (CFM) is a highly effective and well-accepted method for developing latent fingermarks on non-porous substrates. Interactions between the fingerprint residue and the cyanoacrylate vapor cause rapid polymerization resulting in a white polymer coating that enables print visualization. In this process, ECA is fumed onto a non-porous surface containing fingerprints, which forms a white polymer, poly(ethyl cyanoacrylate) (PECA), only on the print ridges, which in turn provides the optical contrast that enables the visualization of a print. ECA not only develops the print, but also fixes and improves visibility of other biological samples, such as saliva, that can be used to identify a criminal without inhibiting the collection and investigative use of DNA information. The chemistry of this process is that there exist chemicals in the latent print that serve as the initiators for the polymerization of ethyl cyanoacrylate to form poly(ethyl cyanoacrylate), which can be easily detected by the human eye. This process is possible because cyanoacrylates are extremely reactive due to their polarized carbon-carbon double bond, which includes two electron-withdrawing groups. The polymerization of highly reactive ECA can be initiated even with a small amount of weak bases and anions. Though a useful technique, the superglue fuming process requires a waiting period to harden and does not always provide a quality fingermark, particularly if it has been exposed to the environment for extended periods of time. Unfortunately, our current understanding of the molecular level processes that occur during superglue fuming is inadequate to provide guidelines This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 4 that can be used to remedy these shortcomings. Thus, in order to develop methods to improve the efficiency and optimize the superglue fuming process, a more careful understanding of the molecular level processes that occur during fingermark fuming and subsequent hardening is needed. For that reason, we have completed a series of experiments that provide insight into the chemical reactions that occur during the superglue fuming and hardening process to provide fundamental information that can be utilized by forensic scientists to rationally optimize the superglue fuming process. We have focused on expanding on our previous results to more completely understand the ability of temperature control and hydration of prints to improve the quality of latent fingermarks. We have also examined the changes that occur to a latent fingermark during the hardening process, with the goal of developing a protocol that will optimize the turn-around time of obtaining a print that can be recorded and compared to a database. The proposed experiments were designed to provide crucial fundamental information that will define and describe the chemical and physical processes that occur during the superglue fuming of latent fingermarks. This in turn will provide a scientific foundation for the validity of the ability of superglue fuming to accurately and truthfully develop the structure of latent fingermarks, providing scientific validation of its ability to faithfully preserve and present the latent fingermark as it was left at the scene. The expertise in our laboratory is polymer science and chemistry. Thus, we view the development of the fingermark during superglue fuming as the polymerization of the cyanoacrylate monomers from the fingermark surface during the fuming process. This polymerization process creates structures that are visible to the eye, which creates the contrast that is needed to visualize the print. The polymerization proceeds by the initiation and chain growth of the cyanoacrylate monomer by chemical components that exist in the latent fingermark deposit. The quality of the developed print is intimately linked to the ability of the chemicals that exist in the fingermark to successfully polymerize the cyanoacrylate monomer, grow structures off the print ridge, and develop the optical contrast needed to view the print. Our previous work in this area provides an interesting foundation and fascinating potential avenues to develop methods to improve the quality of developed fingermarks. For instance, our understanding of the role of water vapor/humidity in the development of latent prints by This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 5 superglue fuming indicates that for any print, aged or new, the solvation by water of the ion that initiates the polymerization process is critical to the formation of PECA. In aged prints, it is known that water is readily lost with aging. Moreover, previous work has shown that merely exposing aged prints to room temperature water vapor is not sufficient to improve their quality when developed by fuming; one way to reconcile these two facts is to consider that the aged prints are not readily re-hydrated. Additional protocols to improve the uptake of water by aged prints, such as super saturation or increased temperature or pressure, are therefore examined as methods to improve the quality of aged prints. Even more exciting is our recent results that begin to explain the role of temperature in the development of latent fingermarks by superglue fuming. These results show that the polymerization of the polymer from the print occurs much more rapidly at lower temperatures. In order to more fully understand the fundamental reasons for, and potentially exploit, this phenomenon to improve the quality of prints developed by forensic scientists, the mass accumulated on reproducibly deposited fingermarks and the molecular weight characteristics of the resultant polymers have been determined and analyzed to provide insight into the fundamental driving force of this behavior. This suggests that lowering the temperature improves the ability of the present initiators to initiate the polymer growth. This is particularly important in relation to developing methods to improve the quality of aged prints that are developed by superglue fuming. It is abundantly clear that aging decreases the number of active initiators present, and in order to improve the quality of the print, the initiators that are present must be more efficient or additional initiators must be added. Our results on the effect of temperature on the growth of PECA from superglue fumed prints strongly suggests that lowering the temperature will make the initiators that are present in the fingermark more efficient in growing polymer chains, and therefore this is an extremely promising and easy method to improve the quality of aged latent prints. We have therefore completed further research to utilize temperature control as a method to improve the quality of fresh and aged latent prints developed by superglue fuming. Findings and Conclusions The Effect of Temperature on the Superglue Fuming of Latent Prints: Using Temperature to Improve the Quality of Aged Latent Prints This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 6 Our initial experiments in this area were completed to document the impact of lowering the temperature of the superglue fuming process on the growth of poly(ethyl cyanoacrylate) from aged latent prints. These results show that lowering the temperature does improve the polymerization of ECA when applied to aged prints as it does to fresh prints. Notably the molecular weight of the grown polymer approaches that which is found in un-aged fumed prints, indicating that the change in initiation and chain growth with temperature is similar for aged and un-aged print and is not affected by degradation or loss of mass of a print during aging. These results therefore suggest that lowering the temperature may improve the quality of the aged print. Determination of the Optimum Temperature for Superglue Fuming Our previous results demonstrate that lowering the temperature of the latent print from 50 to 20 °C dramatically improves the amount of poly(ethyl cyanoacrylate) (PECA) formed on the print during fuming, as well as increases print quality. The current research program focused on optimizing the temperature for fuming to easily characterize the latent fingerprints. These results show that the optimum temperature of the item that is being fumed for fresh latent prints is 8-10 °C. These results are the focus of a manuscript that is in preparation to disseminate this information to Forensic scientists, so that they may take advantage of this information in their fieldwork. Developing methods to control print temperature during superglue fuming in a forensic laboratory The results above clearly demonstrates that the optimum temperature of fuming is ~ 10 °C, which is ~50 °F. These results were expanded to evaluate the quality of fumed latent prints on duct tape, plastic “Ziploc” bags, and soda bottles that were cooled in a refrigerator or freezer, as this cooling protocol is more readily applied in a forensic lab. The goal of these studies is therefore to develop a protocol that may readily be used in Forensic laboratories that will improve the quality of latent prints by cost-effectively lowering the temperature of the fumed prints. Therefore, the effect of placing the sample with the deposited fingerprint in a refrigerator or freezer prior to fuming the print on PECA formation is examined. In particular, the ability of the sample to retain the colder temperature long enough to effect its PECA formation during fuming is assessed. In this experiment, each sample was placed in a refrigerator or freezer for 2 This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 7 days; then removed from the colder environment and brought to the fuming station. Prior to fuming, the temperature of the sample was continuously monitored using an infrared thermometer. In both cases, the plastic substrates return to room temperature within two minutes. Thus, it is clear that the use of a standard refrigerator or freezer is not sufficient to keep the sample at ~ 10 °C during fuming to take advantage of temperature effects of the polymerization of ethyl cyanoacrylate that occurs during the fuming process. The temperature of the three samples was also monitored during fuming of the print surfaces that are placed on a temperature controlled block at 2 °C, 10 °C, 20 °C, and at room temperature. The fuming process brings hot ECA fumes to the print surface, which increases the temperature of the print during fuming. These results indicate that optimum temperature of fuming is between 10 and 15 °C when taking into account the warming of the sample that occurs due to the presence of the warm superglue fumes. Moreover, any protocols that are devised to control the temperature of the fuming process must take into account the presence of the warm superglue fumes. Role of Hydration on the Superglue Fuming of Aged Latent Fingermarks: The goal of this portion of the research program is to investigate methods to aggressively expose aged fingermarks to water with the goal of improving the selective polymerization of ethyl cyanoacrylate from aged prints, consequently improving the quality of the superglue fuming process of aged prints. To realize this goal, we exposed aged prints to water vapor by suspending them above room temperature water vapor or positioning them over a beaker of boiling water. A quartz crystal microbalance monitors the change in mass of new and aged prints during their exposure to boiling or room temperature water vapor to document their ability to take-up water. Somewhat surprising is the fact that the slope of the mass vs. time line for the print suspended above boiling water is negative. This indicates that the mass of the print is decreasing with exposure to boiling water vapor, i.e. that the boiling water vapor washes away the print. Clearly, the exposure of the latent print to boiling water primarily results in loss of print material, a process that is detrimental to the development of the print by superglue fuming. Also, somewhat surprisingly, the exposure of the print to the vapor of room temperature water modestly increases the mass of the print. This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 8 The completed experiments therefore demonstrate that exposure of prints to plain water has very little, if any, effect on the PECA formation during the fuming of fresh or aged latent fingerprints. Exposure to boiling water, however, decreases the amount of PECA grown off of the fresh or aged print; this is attributed to the removal of initiators from the print during exposure, hindering PECA formation and therefore decreasing the quality of prints. Therefore, although eccrine sweat is a water based mixture, these results are consistent with the conclusion that components of the prints other than water initiate polymer growth from superglue fuming, not the water itself. Furthermore, simply rehydrating fresh or aged print by exposure to room temperature or boiling water is not a sufficient method for improving print quality. Boiling water harms prints, presumably by removing initiators by dissolving them into the steam and releasing them from the print before fuming. Optimizing the Turn-around Time of the Superglue Fuming Method The focus of this portion of the project centered on understanding and improving the requirement that fumed prints often necessitate 12-24 hours to ‘harden’ to ensure that the print will not smudge during further analysis. Multiple members of our research team have spent significant time attempting to determine under what circumstances superglue fumed latent prints will smear, and when they won’t. For instance, our group has attempted to identify a set of reproducible conditions that result in fumed latent prints that have a tendency to smear. A variety of factors have been examined in this endeavor, concentrating on the print donors gender and the surface on which the print is deposited. Unfortunately, these investigations have not yielded a reproducible condition where the fumed print smears. With no clear conditions that can be used to reproducibly examine fumed prints that smear, we completed experiments to provide a more careful understanding of the molecular level processes that occur during fingerprint fuming and subsequent “hardening”. We have completed Fourier Transform Infrared spectroscopy (FT-IR) experiments to monitor these molecular level changes during the polymerization of ethyl cyanoacrylate and the hardening process that occurs after polymerization. The results show that there exist differences in the structure of the PECA that is formed by curing and that which is formed on a fumed print, differences that must be understood. These differences could be due to the presence of water in the cured sample that is not as prevalent in This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 9 the fumed sample due to the increased temperature of fuming. The fumed print grows from surface bound initiators, which may result in a different reaction than occurs in the atmospheric curing of the monomer. The current FTIR data is being further analyzed to address these continuing uncertainties. IMPLICATIONS OF POLICY AND PRACTICE: The results of this research program which are most promising to impact policy and practice are the results that provide additional insight into the impact of temperature on the fuming of latent prints. This research program clearly indicates that lowering the temperature of the object on which a fingerprint resides to ~8-10 °C will increase the amount of PECA that is formed during fuming, which in turn improves the quality of the developed print. This has clear implications to the practicing forensic scientists, in that fuming chambers with temperature control should be developed. The results also indicate that the quality of fumed aged latent prints can also be improved by lowering the temperature. Our interpretation of this phenomenon is that the lower temperature improves the efficiency of utilizing the remaining initiators that exist in the print after aging. This provides another parameter to control in lab that can offer an improvement of print quality of aged latent prints. The results that investigated the hardening of the print appear to indicate that there are very few conditions (surfaces, print composition, etc.) that exist for print fuming that result in a latent print that smears. Our interpretation of this result is that the formation of a fumed print that smears is due to specific local environment conditions. This implies that the observation of a print that smears shortly after fuming is indicative of an alteration in the fuming chamber environment, which should be investigated. A reproducible chamber environment should provide the practicing forensic scientist with a fumed print that is robust after a few minutes. This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 10