Annemieke van Dam

Oxidation Monitoring by Fluorescence Spectroscopy Reveals the Age of Fingermarks

No forensic method exists that can reliably estimate the age of fingermarks found at a crime scene. Information on time passed since fingermark deposition is desired as it can be used to distinguish between crime related and unrelated fingermarks and to support or refute statements made by the fingermark donors. We introduce a non-contact method that can estimate the age of fingermarks. Fingermarks were approached as protein-lipid mixtures and an age-estimation model was build based on the expected protein and lipid oxidation reactions. Two measures of oxidation are required from the fingermark to estimate its age: 1) the relative amount of fluorescent oxidation products 2) the rate at which these products are formed. Fluorescence spectroscopy was used to obtain these measures. We tested the method on 44 fingermarks and were able to estimate the age of 55% of the male fingermarks, up to three weeks old with an uncertainty of 1.9 days.

The compatibility of fingerprint visualization techniques with immunolabeling.

The chemical composition of a fingermark potentially holds a wealth of information about the fingermark donor, which can be extracted by immunolabeling. Immunolabeling can be used to detect specific components in fingermarks; however, to be applicable in the forensic field, it should be compatible with commonly used fingerprint visualization techniques. In this study, the compatibility of immunolabeling with two different fingerprint visualization techniques, magnetic powdering and ninhydrin staining, was investigated on fingermarks deposited on glass and on nitrocellulose membranes. With dermcidin as antigen of interest, immunolabeling was performed successfully on all developed fingermarks. We can conclude that immunolabeling is compatible with magnetic powdering and ninhydrin staining, which can be of great forensic value.

Simultaneous labeling of multiple components in a single fingermark.

A fingermark contains important forensic information of the donor, not only in its ridge pattern, but also in the chemical composition of its secretion. Detection and identification of these secretions can be done by immunolabeling. In this study, we describe for the first time a reproducible immunolabeling method that allows the simultaneous detection of multiple components of interest. This method not only reduces the manipulation of fingermarks, but also different types of information can be obtained about the donor in one labeling session. To prove the concept of this technique, we selected two general components as antigens of interest, dermcidin and the human serum albumin. Conjugation of both antibodies to two different synthetic fluorophores, followed by simultaneous incubation of both conjugated antibodies, resulted in successful multiple immunolabeling of fingermarks left on a porous nitrocellulose membrane and on a non-porous glass slide surface. In order to minimize false positives to prevent non-specific binding of antibodies to fingermarks and surface carriers, careful blocking and washing steps were found crucial. With this reproducible protocol, high quality images could be obtained from the multiple labeled fingermarks. In conclusion, simultaneous multiple immunolabeling of antibodies in fingermarks can identify specific components in the secretion of the fingermark, including components related to hygiene, diet, time of day, contacts gender and drug use. Multiple immunolabeling therefore has the potential to make a major impact in the forensic field.

Techniques that acquire donor profiling information from fingermarks — A review

Fingermarks are among the most important types of evidence that can be encountered at the scene of a crime since the unique ridge pattern of a fingerprint can be used for individualization. But fingermarks contain more than the characteristic pattern of ridges and furrows, they are composed of a wide variety of different components that originate from endogenous and exogenous sources. The chemical composition can be used to obtain additional information from the donor of the fingermark, which in turn can be used to create a donor profile. Donor profiling can serve at least two purposes i) to enhance the evidential value of fingermarks and ii) to provide valuable tactical information during the crime scene investigation. Retrieving this additional information is not limited to fingermarks that have been used for individualization, but can also be applied on partial and/or distorted fingermarks. In this review we have summarized the types of information that can be obtained from fingermarks. Additionally, an overview is given of the techniques that are available addressing their unique characteristics and limitations. We expect that in the nearby future, donor profiling from contact traces, including fingermarks will be possible.

Immunolabeling of fingermarks left on forensic relevant surfaces, including thermal paper

The chemical composition of a fingermark contains donor profiling information. Immunolabeling is a technique that can be used to retrieve this chemical information from fingermarks. Additionally, immunolabeling can be used to (re)develop fingermarks. To be of interest in the forensic field, the applicability of immunolabeling should be highly diverse. Therefore, in this study we investigated the applicability of one such method: immunolabeling of fingermarks left on non-porous (aluminum foil, stainless steel keys, plastic sheets, different colored garbage bags, sandwich bags, Ziploc bags), semi-porous (tiles, laminated chipboard), and porous surfaces (thermal and copy paper). Successful immunolabeling of specific components in fingermarks was possible on all surfaces tested, except for laminated chipboards and copy paper. Additionally, high quality images could be obtained from the immunolabeled fingermarks. Surprisingly, fingermarks left on thermal paper showed improved visibility when developed with the immunolabeling method. In conclusion, one intrinsically similar immunolabeling method can visualize fingermarks left on non-porous, semi-porous and porous surfaces.

Immunolabeling and the compatibility with a variety of fingermark development techniques

Much information can be obtained from the chemical composition of a fingermark, which can be helpful in crime scene investigation. Immunolabeling can be used to extract information about the donor of the fingermark and it can also act as a fingermark development tool in sequence with the standard fingermark development techniques. However, before immunolabeling can be used in forensic practice more information on the possibilities and limitations of this technique is required. In this study, our aim was to investigate if immunolabeling is compatible with standard development protocols (indanedione-zinc, indanedione-zinc followed by ninhydrin spraying, physical developer, cyanoacrylate fuming, cyanoacrylate followed by basic yellow staining, lumicyanoacrylate fuming and polycyanoacrylate fuming). Immunolabeling was carried out successfully on all developed fingermarks, whereby dermcidin was selected as antigen of interest. We can conclude that immunolabeling is compatible with a wide variety of different fingermark developers. This finding in combination with previous findings, makes immunolabeling an interesting technique, which can be of great value in the forensic field.

On the autofluorescence of aged fingermarks.

Fingermark autofluorescence changes with time, both spectrally and in total intensity. In this study we investigate which components in the aged fingermarks cause this change in autofluorescent signal. Thin layer chromatography combined with fluorescence spectroscopy was used to identify fluorescent aging products. Based on our results, tryptophan derivatives, including indoleacetic acid, (nor)harman and xanthurenic acid are indicated as important contributors to the autofluorescence of aged fingermarks. Knowledge about which fluorescent aging products are present in fingermarks might be useful in the development of fingermark age estimation methods. This work is part of a larger project of which the major goal is to develop a method to estimate the time of deposition of fingermarks. Additionally, by selective targeting of aging products the development of aged fingermarks might be improved.

Identification and detection of protein markers to differentiate between forensically relevant body fluids

The identification of body fluids at a crime scene is an important aspect of forensic casework analysis, being a source for investigative leads and contributing to case evidence. Yet, current methods for the forensic identification of body fluids suffer from several limitations, ranging from poor sensitivity and specificity, to sample destruction and interference with subsequent DNA analysis. Moreover, current identification assays target only one body fluid at the time. Besides being inefficient in terms of time, money and sample consumption, poor identification methods can also negatively influence the outcome of a (court) case. In this study, eleven potential protein biomarkers and antibodies were selected and assessed on their suitability for serving as identification markers, as a first step towards the development of a new multiplex protein-based body fluid identification assay relying on antigen-antibody interactions. Performing antibody-based dot blot assays, the specificity of the biomarkers for their target body fluids was evaluated, and biomarker detection was studied in diluted, mixed, aged and simulated casework samples. Hereby, nine out of eleven markers were identified as promising biomarkers to identify blood, semen, saliva, urine and sweat. With the identification of these targets and detection antibodies, a major step forward has been taken towards the development of a highly sensitive and specific, fast and non-labour-intensive protein-based body fluid identification assay, suitable for on-site analysis and able to test for multiple body fluids in a single reaction.

Sex determination from fingermarks using fluorescent in situ hybridization

When fingermarks are not suited for automated fingerprint identification, caused by for instance, poor development or when no match can be found in the fingerprint database, the chemical composition can be used to extract additional information about the donor of the fingermark. DNA potentially allows identification, however, the recoverable amount of DNA present in fingermarks is often too low to allow successful DNA-profiling. Therefore, in this research we focus on a method of in situ analysis of the available nucleated cells in fingermarks without prior DNA sampling and extraction and target specific DNA sequences in these cells to reveal potential additional donor profile information. To prove the principle, we determine the sex of the fingermark donor by targeting specific sequences on the X and Y chromosome using fluorescent in situ hybridization. Successful determination of the donors sex based on the presence of male or female cells in the fingermark depositions is demonstrated. Powder dusting and lifting the fingermarks with gelatine lifters does not influence fluorescent in situ hybridization as male and female nucleated cells can be established reliably in fingermark residues. We show that both biometric information and donor characteristics can be obtained from fingermarks including both the morphological and the chemical properties of the fingermark.