Composition of fingermark residue: A qualitative and quantitative review

The capability of Fourier transform infrared (FTIR) spectroscopic imaging to provide detailed images of unprocessed latent fingerprints while also preserving important trace evidence is demonstrated Unprocessed fingerprints were developed on various porous and nonporous substrates Data-processing methods used to extract the latent fingerprint ridge pattern from the background material included basic infrared spectroscopic band intensities, addition and subtraction of band intensity measurements, principal components analysis (PCA) and calculation of second derivative band intensities, as well as combinations of these various techniques Additionally, trace evidence within the fingerprints was recovered and identified

Infrared Spectroscopic Imaging for Noninvasive Detection of Latent Fingerprints

The current paper describes an experimental study of the friction of the human finger pad. The data highlight the role of sweat secretion and contact occlusion in producing wide-ranging values for the coefficient of friction that are particularly sensitive to the tribological configuration, sliding velocity, surface roughness and porosity of the counterbody. In particular, the large coefficients of friction typically observed on dry smooth surfaces are associated with a relatively damp interface, and can be considerably reduced by either decreasing or increasing the interfacial moisture content or by surface roughening. It is concluded that the very large range in the values of the coefficient of friction reported in the literature mainly result from differences in occlusion time associated with different tribological configurations, as well as from variations in surface roughness and finger pad sweat rates.

Friction of the Human Finger Pad: Influence of Moisture, Occlusion and Velocity

The identification of aged latent fingerprints is often difficult, especially for those of children. To understand this phenomenon, the chemical composition of children's versus adults' latent fingerprints was examined over time using Fourier transform infrared microscopy. Hierarchical cluster analysis revealed that children's and adults' prints were distinguishable for up to 4 weeks after deposition, based on differences in sebum composition. Specifically, adults had a higher lipid content than children, but both decreased over time, attributable to the volatility of free fatty acids. The aliphatic CH(3), aliphatic CH(2), and carbonyl ester compositions changed differently in adults versus children over time, consistent with higher cholesterol and cholesteryl esters in children's prints and wax esters and glycerides in adults' prints. Thus, fingerprint composition changes with time differently in children versus adults, making it a sensitive metric to estimate the age of an individual, especially when the age of the print is known.

Chemical Differences Are Observed in Children’s Versus Adults’ Latent Fingerprints as a Function of Time*

This work introduces a new and nondestructive methodology for the collection and chemical identification of latent fingermarks. The main challenges of this work were (a) to find an appropriate medium to lift fingermarks from various surfaces and (b) to develop an analytical approach for the identification of small quantities of sample while avoiding spectroscopic interference from the lifting media. Two different lifting media were evaluated and analyzed by ATR-FT-IR spectroscopic imaging, which affords inherent chemical specificity with rapid acquisition of data. This is the first time that chemical images of latent fingermarks collected with gel lifters from different surfaces have been obtained. Spatially resolved chemical images from different depths within the same sample were obtained using ATR-FT-IR imaging with a variable angle ATR accessory to minimize interference from the substrate. The possibility of obtaining, through the developed methodology, three-dimensional depth profiles of surface cont...

Spectroscopic imaging of latent fingermarks collected with the aid of a gelatin tape.

We report the use of infrared (IR) microspectroscopy for the analysis of fingerprint residues. The advantage of using an IR microscope lies in the ability to visualize and obtain spectra of individual particles and droplets that make up fingerprint ridge deposits at a spatial resolution of approximately 10 μm. Our initial results suggest that infrared microspectroscopy in reflection–absorption mode provides reproducible spectral analysis of fingerprint residue. Since infrared microspectroscopy is nondestructive to the sample, we will be able to study the changes in fingerprint ridge deposits as a function of time. The method holds promise for probing the difference between latent fingerprints of adults and children.

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Diane K. Williams

Papers

Analysis of Latent Fingerprint Deposits by Infrared Microspectroscopy