Latent Prints Research Articles

Fingerprint's Third Dimension: The Depth and Shape of Fingerprints Penetration into Paper—Cross Section Examination by Fluorescence Microscopy

In an attempt to maximize the yield of latent fingerprints from paper items, we conducted a study of a fundamental process between fingerprint deposits and paper. Fingerprint ridges have been observed in the cross section of paper by fluorescence microscopy. It was possible to see, for the first time, how residue from fingerprint ridges is embedded in paper. Undeveloped, latent fingerprints, as well as latent prints developed by the two fluorogenic reagents, DFO and 1,2-indanedione, have been examined. The shape and depth of penetration of fingerprints vary with different types of paper. An inverse relationship between the smoothness of the paper and the penetration depth was observed: higher smoothness values result in lower depths of penetration. High quality prints appear to correlate with an optimal penetration depth-between 40 and 60 microns.

Use of fluorescent dyes for developing latent lip prints

Advances in the sensitivity of techniques used to examine latent prints (finger or labial) make it necessary to find more effective methods of locating prints on different surfaces. The most difficult surfaces are those which are porous or multicoloured, in which case the developed print may not be easily seen. This study analyses the effectiveness of two fluorescent dyes, Nile Blue and Nile Red, in developing both recent and older latent lip prints on porous and multicoloured surfaces. The results indicate that Nile Red is a very effective reagent for the development of latent lip prints on difficult surfaces of this type.

Modifications to the Silver Physical Developer

The silver physical developer is currently the most successful reagent used for visualizing the water-insoluble components (e.g., lipids) of latent prints on porous surfaces. It is normally used after the amino acid visualizing reagents (e.g., ninhydrin and DFO) are used. This work found that the performance of the current formulation of silver physical developer is strongly reduced when the water used is changed from the usual distilled water to the more purified reverse osmosis/deionized (RO/DI) water. Based on numerous experiments involving the systematic variation of the component concentrations, the performance was restored and even improved by reducing the concentration of all the components (except that of the ferric salt) and by including malic acid in the formulation. These modifications resulted in a new silver physical developer formulation that performs as well as or better than the current formulation and is less expensive to make.

The Effects of Latent Print Processing on Questioned Documents Produced by Office Machine Systems Utilizing Inkjet Technology and Toner

Counterfeiting of currency and identity documents, death threats, illegitimate business transactions, and terrorist-related activities are some examples of the types of crimes that often involve documents produced from printers and copiers. Although standard protocol typically requires a questioned document (QD) examination prior to latent print (LP) processing, occasionally, items of evidence may be submitted for a QD examination following the application of a series chemicals utilized in the development of latent fingerprints. In such cases, the forensic examiner must take into account any previous treatments prior to initiating an examination on documents produced with a printer or copier. This study was devised to examine the effects of a latent print development technique [ninhydrin, physical developer, and a bleach enhancer] on the physical and chemical examination of documents produced from copiers and printers.

A new chemical aid for criminal investigation: dyes and latent prints

Criminalistics is a field in which there are many opportunities for the practical application of chemical reagents and the use of analytical methods that provide answers to enigmas at crime scenes. Common reagents in biochemical and medical test methods can be useful for criminalistics (forensic science). Dyes are one type of reagent that can be used in obtaining crime scene evidence. This work describes a new application of CI Solvent Black 3 dye in the location of latent fingerprints. The results show that CI Solvent Black 3 can be successfully applied in the location and development of recent and non‐recent latent fingerprints on porous surfaces.

Review of: Contrast: An Investigator's Basic Reference Guide to Fingerprint Identification Concepts

Abstract This book was written as a guidebook to illustrate the basic concepts involved in the science of fingerprints and fingerprint identification and, according to the author, is intended for new and experienced crime scene investigators, patrol officers, attorneys, and students "who seek to add fingerprint identification to their investigative skills." The guidebook is meant to give a general background in fingerprint concepts and the reader should not view himself or herself as proficient in fingerprint identification after reading this book. As the author points out in the introduction, "On the average, it takes about 5 years of training and fieldwork to be considered a proficient and experienced fingerprint specialist." At the very least, a fingerprint identification expert should successfully complete a two to three year training program in all facets of fingerprints at a qualified training laboratory under the guidance of court recognized experts to be considered an expert in latent prints. The author correctly points out that becoming proficient in the area of fingerprints is basically a learned experience from on-the-job training, but that the basis for fingerprint identification and advances in processing techniques makes it desirable to have knowledge in scientific disciplines.

The influence of polymer type, print donor and age on the quality of fingerprints developed on plastic substrates using vacuum metal deposition

This study investigated fingerprint development on five different polymer substrates using vacuum metal deposition (VMD). The conditions required for optimum development are shown to depend on a number of factors. No one set of conditions will result in good development in all situations. Polymer type has been confirmed as a major factor in determining the types of development that will occur and the optimum VMD conditions required. For more consistently successful VMD development, polymer type should be determined before selecting conditions. While polymer type is a key factor in determining optimum development conditions, there may be variation of the optimum conditions within a polymer type, most likely due to the presence of additives in the plastic. The heaviness of a latent print, i.e. amount of residue that constitutes the print, also affects the VMD conditions required. The donor, manner of deposition, and age of a print affect the heaviness of the deposit. The heavier the print, the higher the gold count necessary for successful VMD development. The occurrence of ‘empty prints’ (i.e. zinc deposition on the general background but not on or between the print ridges) was found to be related to polymer type and print heaviness. Heavy prints on PVC and PET are the most likely to be ‘empty’ after VMD treatment. The development of empty prints may be due to the diffusion of print residue into the print valleys. Pre-treatment with cyanoacrylate fuming was also found to affect VMD development. In particular, it was shown that cyanoacrylate pre-treatment was beneficial for print development on PET and PVC. The results of this study were used to formulate guidelines for use as an aid by laboratories using VMD in casework.

Vacuum metal deposition: developing latent fingerprints on polyethylene substrates after the deposition of excess gold

A previously identified difficulty with the development of latent fingerprints on low-density polyethylene (LDPE) by vacuum metal deposition (VMD) is that excess gold deposition prevents effective zinc deposition and so inhibits latent print development [1]. The investigation of a means to correct for excess gold deposition was the basis for this study. Exposure to zinc and the readmission of air into the vacuum chamber followed by VMD development results in the deactivation of the initial gold clusters due to the formation of zinc oxide and the adsorption of air and water molecules. As a result, the majority of the gold deposited during the second treatment creates new gold clusters rather than adding to the gold clusters previously formed. After excess gold deposition on LDPE, the deposition of 1.5 times the optimum gold amount will result in good-quality normal development. The results also indicate that, on all surfaces, at least twice the initial gold count should be used for re-treatment when further development is required after air has been readmitted to the chamber.

Powder method for detecting latent fingerprints: a review

The powder technique for detecting latent fingerprints involves the application of a finely divided formulation to the fingermark impression, generally with a glass-fibre or a camel hair brush. The powder gets mechanically adhered to the sweat residue defining the ridge pattern. The furrows which are devoid of the fingerprint residue, do not adhere the powder onto them. The final outcome is that the powder formulation sticks to the ridges, but is easily blown off the furrows. Since the powder is normally coloured, the ridge pattern becomes visible and the latent print is said to have developed.

Processes Involved in the Development of Latent Fingerprints Using the Cyanoacrylate Fuming Method

Chemical processes involved in the development of latent fingerprints using the cyanoacrylate fuming method have been studied. Two major types of latent prints have been investigated-clean and oily prints. Scanning electron microscopy (SEM) has been used as a tool for determining the morphology of the polymer developed separately on clean and oily prints after cyanoacrylate fuming. A correlation between the chemical composition of an aged latent fingerprint, prior to development, and the quality of a developed fingerprint has been observed in the morphology. The moisture in the print prior to fuming has been found to be more important than the moisture in the air during fuming for the development of a useful latent print. In addition, the amount of time required to develop a high quality latent print has been found to be within 2 min. The cyanoacrylate polymerization process is extremely rapid. When heat is used to accelerate the fuming process, typically a period of 2 min is required to develop the print. The optimum development time depends upon the concentration of cyanoacrylate vapors within the enclosure.

Recent advances in photoluminescence detection of fingerprints.

Photoluminescence detection of latent fingerprints has over the last quarter century brought about a new level of fingerprint detection sensitivity. The current state of the art is briefly reviewed to set the stage for upcoming new fingerprint processing strategies. These are designed for suppression of background fluorescence from articles holding latent prints, an often serious problem. The suppression of the background involves time-resolved imaging, which is dealt with from the perspective of instrumentation as well as the design of fingerprint treatment strategies. These focus on lanthanide chelates, nanocrystals, and nanocomposites functionalized to label fingerprints.

Vacuum metal deposition: factors affecting normal and reverse development of latent fingerprints on polyethylene substrates

Vacuum metal deposition (VMD) is an established technique for the development of latent fingerprints on non-porous surfaces. VMD has advantages over cyanoacrylate fuming, especially in circumstances where prints are old, have been exposed to adverse environmental conditions, or are present on semi-porous surfaces. Under normal circumstances, VMD produces ‘negative’ prints as zinc deposits onto the background substrate and not the print ridges themselves. A phenomenon of ‘reverse’ development, when zinc deposits onto the print ridges and not the background, has been reported by many authors but its causes have not been conclusively identified. Four plastic substrates were used in this study and these could be easily divided into two groups based on the types of development observed as the amount of deposited gold was increased. On group I plastics, identified as low-density polyethylene (LDPE), normal development then reverse development and finally no development resulted with increasing gold. On group II plastics, identified as high-density polyethylene (HDPE), normal development then over-development and finally poor-quality normal development resulted with increasing gold. Our results suggest that the difference between these plastic types causes variations in the gold film structure which in turn dictates the nature of the zinc deposition. On group I plastics, the structure and thickness of the gold film has been identified as the critical factor in the occurrence of normal or reverse development. Thin gold films on plastic substrates form small ‘clusters’ (or agglomerates) rather than the atoms being uniformly spread over the surface. The size and shape of these clusters is critical. Once the clusters reach a certain morphology, they no longer act as nucleation sites for zinc, and hence, zinc will not deposit onto the substrate. On group II plastics, results suggest that the gold clusters are smaller and more densely packed. Hence, even though the same amount of gold has been deposited, the gold clusters in this case do not reach the critical morphology and so continue to act as nucleation sites for zinc. Typically, zinc will not deposit onto the fingerprint ridges as the gold nucleation sites are buried within the print residue. However, when more gold is deposited, gold emerges at the surface of the latent print allowing zinc deposition onto the ridges. The rate of gold evaporation was found not to affect the structure of the gold film, although a slower rate of evaporation resulted in more effective deposition.

Review of Fingerprint Detection with Lasers, Second Edition

Abstract This revised and expanded edition of Dr. Menzel's 1980 book is lcome book for latent print examiners, forensic scientists, and scientists interested in the fascinating field of latent print visualization. It updates his previous book by including new and advanced optical imaging techniques that have emerged in the last 20 years. These include CCD cameras, near-infrared imagers, ultraviolet imagers, and acousto-optical tunable filters. It also treats new developments in latent print visualization that have occurred during this time such as the use of DFO, ninhydrin analogues, rare-earth chelates, 1,2-indanediones, multi-metal deposition method, and DMAC. Each chapter is well referenced.

Evaluation of 1,2-Indanedione and 5,6-Dimethoxy-1,2-Indanedione for the Detection of Latent Fingerprints on Porous Surfaces

The ability of 1,2-indanedione and 5,6-dimethoxy-1,2-indanedione to detect latent prints on porous surfaces, as compared to DFO and ninhydrin, has been evaluated. Comparisons of prints developed under various conditions determined the optimum development conditions for the new reagents. The indanediones tested were found to have lower detection limits for glycine. The carrier solvent used was found to affect the quality of the prints developed. In Arklone, the new reagents developed prints that displayed superior luminescence to those developed with DFO. In HFE 7100, 1,2-indanedione and 5,6-dimethoxy-1,2-indanedione gave superior luminescence to DFO after zinc salt treatment and cooling with liquid nitrogen, both of which improve the luminescence of prints developed with 1,2-indanediones. 1,2-Indanediones could offer less expensive but effective alternatives to DFO. With further optimization, the new reagents may supersede DFO as the method of choice for the detection of latent fingerprints on porous surfaces.

Latent Fingerprint Visualization by 1,2-Indanedione and Related Compounds: Preliminary Results

Abstract A number of vicinal cyclic diketones, most of them belonging to the 1,2-indanedione series, have been prepared and tested as potential reagents for latent fingerprint development. Unsubstituted 1,2-indanedione and a number of its mono- and dimethoxy- derivatives exhibited excellent properties as fluorogenic reagents for latent prints on paper. Structural modifications, such as substitutions at position 3, omission of the benzene ring or increase of the five-membered to a six-membered ring, considerably reduced this activity. Quite surprisingly, benzo[f]indane-1,2-dione, which was synthesized for the first time in this work, was significantly inferior to 1,2-indanedione as a fingerprint reagent. Even at this stage, before optimization of the reaction conditions, it can be said that some 1,2-indanediones are at least as sensitive as DFO. Their solubility in nonpolar solvents and relative case of preparation are further advantages. It is the authors' opinion that 1,2-indanedione itself may soon become a practical fingerprint reagent.

1,2-Indanediones: New Reagents for Visualizing the Amino Acid Components of Latent Prints

Abstract A new class of reagents, 1,2-indanediones, was evaluated for latent print visualization on paper. Tests were carried out for fingerprints and amino acid stains. Selected 1,2-indanediones give fluorescent development superior to DFO. Zinc salt treatment further enhances the sensitivity. The new reagents can be obtained from inexpensive starting materials in a short reaction sequence.

Base-activated latent fingerprints fumed with a cyanoacrylate monomer. A quantitative study using Fourier-transform infra-red spectroscopy

It is shown for the first time that a Fourier-transform infra-red spectroscopic study of cyanoacrylate fumed fingerprints provides a non-subjective confirmation of visual estimates of polymer deposition as made by fingerprint experts. The greatest degree of polymer deposition on latent prints within the parameters of the experiment were produced by prior exposure to ammonia followed by fuming with methyl cyanoacrylate monomer. The method with base activation also permits further quality enhancement of prints previously developed by the current method.

Use of Acidified Hydrogen Peroxide to Remove Excess Gun Blue from Gun Blue-Treated Cartridge Cases and to Develop Latent Prints on Untreated Cartridge Cases

Abstract A formula used by firearms and toolmark examiners to clean lead residue from bullets was also found to remove excess gun blue coating from metal cartridge cases. It consists of a mixture of acetic acid and hydrogen peroxide and works by oxidizing the coating back into solution. This explanation allows one to determine the optimum proportion of the mixture. Acidified hydrogen peroxide formulas were also found to “clean” (oxidize or etch) metal cartridge cases in areas where there was no sebaceous latent print material (or other substances that resist oxidation). The subsequent treatment of these “cleaned” cartridge cases with gun blue to enhance the latent print contrast was also considered.

Latent Fingerprint Processing by Ruthenium Tetroxide Method

The method studied in this paper is developing latent fingerprints based on ruthenium tetroxide (RuO4) method. Ruthenium tetroxide fuming promptly react with various organic compound, particularly oils or fats contained in sebaceous secretions in latent print and producing brownish black or black ruthenium dioxide (RuO2). Ruthnium Tetroxide is yellow, volatile crystails (melting point; 25.5°C, boiling point; 100.8°C) at room temperature. Conventional methods using RuO4 have been almost impractical because it is very difficult to handle by its strong oxidizability. Additionally because of the two liquid method, it is not only troublesome to produce RuO4 fumes immediately before developing latent fingerprints, but also is difficult to produce necessary ammounts of RuO4 fumes. In this method, these problems were resolved by utilizing a saturated hydrocarbon halogenid solution of RuO4

A modified cyanoacrylate technique utilizing treated neutral filter paper for developing latent fingerprints

The cyanoacrylate fuming method has been improved by using treated neutral filter paper. A procedure is described and results show that latent prints on skin or other difficult surfaces can be developed effectively and rapidly. Enhancement of developed fingerprints can also be achieved by the use of fluorescent dyes.