Detection and Enhancement of Latent Fingerprintsrints on Black Electrical Tape

Abstract: This study investigated a selection of methods to detect latent fingermarks on black electrical tapes. Subsequently, a sequence of techniques was developed and is suggested as a standard operating procedure.

Different formulations of white and silver powder suspensions were developed by comparing Citron detergent and Kodak Photo-Flo as the surfactant in the suspension. A mixture of both surfactants in the suspensions repeatedly produced greater fingerprint development on the adhesive side compared to using either one on its own.

Two techniques consistently performed to a higher standard for both fresh and aged marks on the adhesive side: cyanoacrylate followed by a combined basic yellow 40/basic red 28 stain and the white powder suspension. The contrast, sharpness, ridge detail, and simplicity of preparation and application achieved with both of these techniques made them superior to the other methods tested. The sequence that proved successful on the adhesive side of all tapes tested involved cyanoacrylate fuming and application of a fluorescent stain, followed by white powder suspension, and finally gentian violet with a transfer of developed marks if necessary. This sequence allowed maximum development and the greatest enhancement of latent marks, without causing the destruction of the deposit for subsequent methods. Latent fingermarks on the backing (nonadhesive side) of the electrical tape were also successfully developed with cyanoacrylate and the fluorescent stain, so treatment of the backing could be incorporated into the sequence.

Introduction

Adhesive tape can be found at crime scenes involving abductions, illicit drugs, and explosive devices. Electrical tape, in particular, is frequently used as a wrapping for drug packages, as reinforcement for the stocks of sawed-off firearms, for electrical wiring applications, or as a means to bind a victim. Amongst various types of evidence, such tapes may bear latent fingermarks on the adhesive side or on the backing.

The most well-known fingermark detection method, which has been applied successfully to the adhesive side of a variety of tapes, is the sticky-side powder method. This method involves mixing sticky-side powder with Kodak Photo-Flo and water to form a thick suspension, which is painted onto the adhesive surface using a brush and then rinsed off using water [1]. A more recent technique is the detergent and black powder process whereby black fingerprint powder, Liqui-Nox detergent, and distilled water are combined, brushed onto the tape specimens, and then rinsed with water [2]. A detergent, such as Liqui-Nox or Photo-Flo, is used because it contains a surfactant that reduces the surface tension of the liquid, allowing easier spreading. This means that once the powder is suspended in the liquid, the whole mixture can be applied more evenly and uniformly than if the powder was just added to water.

Similar formulations in the early stages of use include titanium dioxide (white powder) added to Photo-Flo solution, applied using a brush to the adhesive side, and then rinsed off with water [3], or using detergent instead of Photo-Flo [4]. Titanium dioxide is a very fine, nontoxic, nonflammable, white powder that has not been extensively used for developing latent marks on adhesive tape, but has been proven useful for the enhancement of fingermarks on dark surfaces. It has been suggested that, when used as a substitute for sticky-side powder, titanium dioxide can produce superior results on black electrical tape and can also develop prints on both sides of the tape [5]. The small particle reagent (SPR) technique can also develop latent marks on dark backgrounds, such as both sides of black electrical tape, by mixing molybdenum disulfide (a light grey powder) with detergent, followed by dilution with water and application as a spray.

There has been some success with fluorescent products such as Ardrox for ridge development on both sides of black tapes. This method involves mixing Ardrox with detergent and distilled water to produce a thick, milky-yellow solution. This is then painted onto the tape, rinsed off, and dried before being examined under UV light to observe fluorescence [6].

Gentian violet is a dye that produces a purple colored image because of its absorption by the fatty constituents of the sebaceous deposit. The method generally involves dissolving gentian violet and phenol in ethanol and then diluting with water before use [7]. In the case of dark surfaces, developed marks can be transferred to fixed photographic paper for visualization. The obvious drawback is that gentian violet is toxic, is an irritant to the skin and eyes, and is a suspected carcinogen. Phenol is also toxic, causes burns, and can be absorbed through the skin.

Most processes for fingermark development produce dark colored prints. This can be a problem for latent marks on dark surfaces because of the poor contrast. For dark adhesive tapes, such as black electrical tape, some methods from the ones discussed above may prove more effective than others. Techniques that produce white or fluorescent ridges on a dark background are likely to be more suitable for latent mark development on both sides of black or dark colored tapes. Alternatively, it may be necessary to transfer the developed marks onto photographic paper to enable better contrast and easier photography. It may even be useful to substitute ash, grey, or silver colored powder for black powder in a suspension formulation to increase contrast against a black background.

Frequently, it is desirable and more effective to use more than one method, in sequence, to locate latent marks. However, the use of one method may ruin subsequent chances of locating latent marks with other techniques. Problems can arise when treating adhesive tape because both sides generally need to be treated with different processes (although some methods can be applied to both sides). It is therefore necessary that a sequence be evaluated in order to ensure that the best possible detail is brought out in any potential fingermarks and that the quality of any prints is not compromised on either side of the tape. This includes incorporating techniques for developing latent marks on the backing (such as cyanoacrylate and stains) with techniques for developing marks on the adhesive side (such as powder suspensions).

The objective of this study was to investigate a selection of methods to detect latent fingermarks on black electrical tapes in order to determine the most appropriate sequence to be used in routine casework.

Method and Materials

Five brands of black electrical tape were selected for analysis from major hardware and department stores. Each tape underwent treatment from eight techniques for both aged (35 days old) and fresh latent marks. The techniques that did not require a transfer to photographic paper were compared directly, side-by-side, on the same piece of tape for the same set of prints to assess their ability to develop latent marks. The techniques assessed were as follows:

1. White powder suspension
2. Cyanoacrylate and fluorescent stain
3. Silver powder suspension
4. Ardrox
5. Sticky-side powder (plus transfer)
6. Black powder suspension (plus transfer)
7. Gentian violet (plus transfer)
8. Small particle reagent (SPR) (plus transfer)

Some techniques required initial testing to develop the most suitable formulation for use. This involved such things as choosing between detergent and Photo-Flo as the surfactant, or varying the concentration. Formulations had to be developed for the following three techniques:

1. White powder suspension
2. Silver powder suspension
3. Ardrox

The final stage of the project was to evaluate a possible sequence to be applied as standard practice for fingermark development on black electrical tape. This involved applying certain techniques in different arrangements in order to achieve the greatest fingermark enhancement. Once a sequence was found to be appropriate, it was also applied to the tape backing to ensure that development on this surface was also optimized.

Latent Fingermark Deposit

The tapes were cut into 15 cm lengths and a set of prints was placed on the tape (adhesive or nonadhesive side). Donor samples consisted of three fingermarks from the index, middle, and ring finger of the donor’s right hand. Before depositing their prints, the donors were required to rub their fingertips over their face or another part of the body with sebaceous secretions (e.g., the back) and then place their prints on three pieces of tape so as to provide three sets of fingermarks with different amounts of sebaceous material:

1. Strong marks "charged" with sebaceous components
2. Medium marks containing less sebaceous material
3. Weak marks containing mostly eccrine deposits

The tape was cut through the center of the middle fingermark, dividing the set in half, so the left and right side could be treated with two different techniques. This allowed for direct side-by-side comparison of any two techniques so that the differences or similarities in performance could clearly be seen. The comparison was carried out in duplicate, with each technique applied to the opposite side. This was to account for any differences in the applied pressure or the oil content of one particular fingertip of the donor and to prevent reaching a conclusion that one technique did not perform as well when, in fact, it was the result of differences in the latent deposits.

Formulations

For white and silver powder suspensions, three different formulations were tested:

1. Powder + Citron detergent + water
2. Powder + Kodak Photo-Flo 200 + water
3. Powder + Citron + Photo-Flo + water

Citron detergent is an all-purpose neutral liquid cleaner found in the laboratory, but it is also used in commercial and domestic areas (e.g., dishwashing liquid, laundry detergent, floor washing, car wash). The amount of powder, detergent, Photo-Flo, and water was varied in each formulation until the most suitable consistency was created to best develop the latent marks.

The Ardrox formulations that were developed and compared varied only in the dilution and consisted of Ardrox plus Citron detergent plus water. The sticky-side powder formulation was prepared as suggested in the literature [1]. SPR, stock and working solutions of gentian violet, the combined basic yellow 40 and basic red 28 stain (BY40/BR28), and rhodamine 6G stain were prepared according to the Australian Federal Police Workshop Manual [7]. The black powder suspension was prepared according to methods previously evaluated [8]. For all powder suspensions, the three components were mixed using a brush until a thick suspension formed, much like paint. When powder suspensions of this type are left to stand for significant periods, the powder tends to separate from the mixture and the mixture must be thoroughly remixed prior to use.

Application of Techniques

• White powder suspension: The suspension was applied as a thin paste using a brush so as to form a thick layer on the tape. This was rinsed immediately using slow running deionized water to remove excess powder. The process was repeated 3 times to achieve the greatest development. The tape was then dried at room temperature in open air.
• Silver powder suspension: The procedure was the same as for white powder suspension, but only two coats were applied.
• Black powder suspension: The procedure was the same as for white powder, but only two coats were applied and each was left on for 20 seconds before rinsing. The processed print was then transferred to wet photographic paper after dampening the paper with deionized water. The tape was applied to the paper, sticky-side down, and gently smoothed over to avoid trapping any water or air bubbles. This was then placed between two sheets of paper towel and was placed in a hot press for four minutes (approximately 170 ºC). After four minutes, the tape was removed and, while still hot, was gently peeled off the paper. Developed black fingermarks were transferred onto the photographic paper.
• Sticky side powder: The procedure was the same as for black powder suspension, but three coats were applied and each was left for 20 seconds before rinsing. The same transfer process to photographic paper was applied.
• Small particle reagent (SPR): The spray bottle was shaken well before application to help resuspend any settled molybdenum disulfide particles. The SPR was continuously sprayed onto the adhesive side of the tape for 10 to 15 seconds and was then rinsed with a gentle flow of deionized water.
• Gentian violet: The tape was treated by immersing it in the gentian violet working solution and agitating it for approximately 45 seconds. The tape was then removed and rinsed under deionized water until the water ran clear and the background staining was removed. The tape was then immersed in a beaker of Photo-Flo solution (3 mL Photo-Flo 200 diluted to 200 mL with deionized water), removed, and developed marks were transferred to photographic paper in the same manner as for black powder.
• Ardrox: The prepared mixture was painted onto the adhesive side of the tape using a brush. Within 2 seconds, the mixture was thoroughly rinsed off using deionized water. The specimen was then dried in open air at room temperature.
• Cyanoacrylate fuming: Both sides of the tape underwent treatment with cyanoacrylate vapor in a forensic fuming cabinet (Carter-Scott Design, Australia), resulting in the formation of a hard white polymer on the latent print deposit.

Fingermark Imaging and Recording

The VSC 2000/HR Video Spectral Comparator (Foster and Freeman, UK) was used as the imaging system. The prints that were photographed under white light had an integration time of 1/30 second, unless otherwise specified. The prints that were visualized under fluorescence excitation at 440-580 nm with a 610 nm barrier filter (BY40, BR28, and rhodamine 6G stains) were photographed with an integration time of 1/4 second. Prints that were visualized under ultraviolet light (Ardroxtreated prints) were photographed with an integration time of 1/2 second.

Comparison of Techniques

The preliminary investigation involved determining a suitable formulation for the white powder, silver powder, and Ardrox mixtures. The formulation that was found to perform the best from these preliminary investigations was used in the comparison testing with the other techniques. There were eight methods in total to be evaluated, but four of these required transfer to photographic paper for visualization. The four methods not requiring transfer to photographic paper were all compared side-by-side. For the techniques that required transfer to photographic paper, the comparisons were first carried out between black powder, sticky-side powder, and SPR because these techniques all produced dark grey or black ridges. Given that these techniques were all very similar, it was decided that gentian violet did not need to be directly compared to all of them, but instead only to the one that was found to perform best. When the superior “dark ridges” technique was identified, it was compared side-by-side (on photographic paper) to gentian violet. All of the above comparisons were applied to both the fresh and aged latent marks.

A judgement was made as to the performance of each technique based on various characteristics of the processed fingermarks:

• Quality of ridge detail (evidence of dots, ridge endings, dividing ridges, or further detail such as pores)
• Contrast and intensity
• Sharpness (extent to which the ridge detail was blurred or separated)
• Area (e.g., development of whole print, or just the edges, top or bottom)
• Background staining or discoloration
• Uniformity of treatment (evidence of streaks or smudges)

Sequencing

The main methods that were investigated for a possible sequence were white powder suspension and cyanoacrylate fuming plus stain. Because the black powder and gentian violet transfers had also been successful in the comparisons, these were investigated as a final stage in the case of unsatisfactory development, poor contrast, or discoloration from the fuming and white powder.

Latent fingermarks on the backing side of the tape were treated with cyanoacrylate and then were stained because this is the method of choice worldwide for treating nonporous items in the laboratory. Once this was demonstrated as being successful, the backing of all tapes was then incorporated into the established sequence to determine whether the sequence was versatile enough to be applicable for both surfaces of electrical tape.

Results and Discussion

Formulation of Powder Suspensions

• White Powder Suspension

All three of the formulations that were tested produced some ridge development, but the quality varied. The blended mixture, containing both Photo-Flo and Citron detergent, consistently developed fingermarks of a higher quality. The Photo-Flo formulation developed marks that were very faint. The detergent formulation developed marks that were slightly better than the Photo-Flo formulation, but the background was discolored markedly to a light grey color (even after one coat), significantly reducing contrast. The quality of the developed marks from both the detergent-only formulation and the Photo-Flo-only formulation was also shown to decrease with depleted latent marks (medium and weak deposits). The final formulation was developed so as to maximize clarity and contrast, but with minimal background staining. This meant having the right proportions of detergent and Photo-Flo (final mixture contained 0.75 g powder, 1 mL Photo-Flo, 1.5 mL Citron detergent, and 2 mL water). The blended mixture proved a more effective technique, in that the contrast was remarkably enhanced, there was less background discoloration than with using detergent alone, and the suspension tended to take hold of the latent deposit much better. It worked consistently for all five tapes, and it successfully developed fresh and aged fingermarks of strong, medium, and weak nature.

• Silver Powder Suspension

The results for the development of a silver powder suspension were similar to those for the white powder suspension. The detergent-only mixture stained the background of all tapes excessively, after only one coat, and the Photo-Flo-only mixture developed nil or very faint fingermarks. The blended mixture allowed for better contrast than the detergent formulation and greater development than for Photo-Flo alone. The silver powder bonded to the adhesive background to a greater extent than did the white powder, markedly decreasing the quality of development.

Staining Cyanoacrylate-Developed Prints

Latent fingermarks on the adhesive side of the tapes were subject to cyanoacrylate fuming. Two stains were then investigated for treating marks developed by this technique: BY40/BR28 combined stain and rhodamine 6G. BY40/BR28-treated marks were found to fluoresce much brighter than those treated with rhodamine, thereby increasing sharpness and contrast (Figure 1). Rhodamine not only was faint in its fluorescence but also was less selective toward the deposit, staining the background and making visualization very difficult. For this reason, the combined BY40/BR28 stain was used in the subsequent comparisons.

Evaluation of Techniques

• Cyanoacrylate plus BY40/BR28 stain: Cyanoacrylate fuming proved successful on both fresh and aged marks for all the tapes tested. Fuming times of 5, 10, 15, 20, 25, and 30 minutes were tested. The difference in development was obvious up to 20 minutes, but could not be detected between 20 and 25 minutes. Thirty minutes of fuming, however, proved too long, and some ridge fusing (overdevelopment) was evident after staining. For this reason, all the tapes holding both fresh and aged fingermarks were fumed for 25 minutes. Most of the time only minimal differences could be observed between the strong marks and the depleted marks for each tape (Figure 2).
  
  Cyanoacrylate is known to be more effective on fresh latent marks. However, it successfully developed marks that were 35 days old on all five tape samples. Overall, cyanoacrylate was found to be one of the most successful techniques for developing fresh and aged prints on the adhesive side of all five tapes and gave results comparable with those obtained using white powder suspension.
  
  
• White powder suspension: The white powder suspension that was developed performed well for strong and depleted fingermarks, both in the detail and intensity of the processed deposit (Figure 3). It occasionally caused some minimal background staining that decreased the contrast, making visualization difficult. This could be reduced by rinsing the suspension off immediately and by only applying the mixture two to three times. When the contrast was good, it was often possible to see not only ridge endings and dots, but also finer detail such as pores and creases. Overall, the detail developed by the white powder suspension method for fresh and aged latent marks was repeatedly comparable to, if not better than, cyanoacrylate, but was far superior to the silver powder suspension and Ardrox.
  
  
• Silver powder suspension: The silver powder suspension was not successful because of the background staining that occurred. Had the silver powder been more selective toward the latent det, the method would have been improved because the powder was able to develop ridge detail. As mentioned above, in comparison to the white powder suspension, the method was inferior even though the formulations were identical (Figure 4). The method was clearly unable to develop aged marks on any of the tapes and showed little or no detail for depleted deposits. Similarly, the method was mediocre compared to cyanoacrylate fuming and staining, and was comparable to, if not worse than, the faint marks developed by Ardrox. By applying more coats of the suspension or allowing more time to pass before rin, the tape only became more discolored, without any improvement in the fingermark development.
  
  
• Ardrox: As previously mentioned, Ardrox had several drawbacks that made visualization and photography difficult. These included very bright staining of the background and complete vanishing of the image after 12 hours (significant fading was noticed after only 15 minutes). Because the treated deposits produced only weak fluorescence, these complications made the technique even less useful for this type of fingermark processing. Ardrox was not suitable for aged marks, but it developed faint ridge detail for fresh deposits. For depleted latent marks, the detail was usually very faint and difficult to photograph.
  
  
• Transfers: Of the four methods that were transferred onto photographic paper, gentian violet and black powder were superior to sticky-side powder and SPR. The black powder suspension was compared to sticky-side powder and SPR and was found to develop darker, more intense marks (Figure 5). The quality of the ridge detail, however, was comparable for all three techniques, producing grey or black ridges. The drawback for the sticky-side powder and SPR method was that the ridges were too faint for adequate examination once they were transferred, but too dark on the tape to allow for sufficient contrast.
  
  Once it was established that the black powder suspension was superior to the other techniques, this was then compared to gentian violet that produced dark purple ridges. The intensity and detail of the transferred fingermarks were comparable for both methods on all five tapes. Gentian violet-treated marks were dark purple on a light purple background after transfer, and the development was uniform for the entire deposit. The obvious drawback is that the reagent is highly toxic, adequate safety equipment needs to be worn at all times, and all work must be carried out in a fume hood.

Sequencing

It was decided that any possible sequence should begin with either cyanoacrylate or white powder suspension, because these techniques were found to be superior to all others and were comparable to each other. If cyanoacrylate was to be first, then it needed to be investigated whether white powder suspension should be applied before or after a stain. The results showed that cyanoacrylate could successfully be applied before the white powder suspension without destroying the latent residue necessary for the subsequent application of the white powder (Figure 6).

Similarly, the adhesive side was fumed with cyanoacrylate after the application of white powder to determine whether white powder prevented the cyanoacrylate from bonding to the deposit. The BY40/BR28 stain was applied after each of the two situations indicated above. The stain did not work after either of the combinations on all five tapes. This suggests that, in the first instance (cyanoacrylate then suspension), the stain could not dye the superglue ridges because the white powder was covering the ridges and, in the second instance (suspension then cyanoacrylate), the cyanoacrylate was not able to react with any fingermark residue because the white powder was “shielding” the deposit.

The stain, therefore, needed to be applied after cyanoacrylate fuming and before the white powder. For all five tapes tested, this order of application was successful (Figure 7). It was therefore inferred that applying both cyanoacrylate and a stain did not have a negative effect on the subsequent application of the white powder suspension. The white powder sometimes helped to hide some of the background discoloration caused by the staining, thereby increasing the contrast and making the details easier to see.

As mentioned above, a transfer was considered appropriate in the sequence if poor results and low contrast were evident from the first sequence of techniques. Since both gentian violet and black powder were found to be the best techniques to use for transfers, these were tested as the final stage of the complete sequence. No fingermarks were visible on photographic paper after black powder treatment and transfer for any of the five tapes. The paper simply turned grey and smudgy. Gentian violet, however, produced dark purple marks of good detail and contrast after transfers from all five tapes. This suggests that the cyanoacrylate, fluorescent stain, and white powder suspension do not prevent the subsequent application of gentian violet to further enhance the latent deposits (Figure 8).

Incorporating the Backing into the Sequence

The nonadhesive backing is obviously less complicated to treat than the adhesive side. In fact, cyanoacrylate is the standard method of choice for developing fingermarks on the backing of most adhesive tapes, black electrical tape included. The fact that the optimized sequence includes cyanoacrylate as its first treatment made it easier to incorporate the backing into the sequence because it was not affected or did not have to be protected by any other method before it could be considered. Cyanoacrylate plus BY40/BR28 stain was found to be successful for treating the backing of all tapes tested. Both the fresh and aged latent marks that were treated were developed to a high standard, showing good contrast, detail, and sharpness. An attempt was made to apply the white powder suspension to the backing after it had been fumed and stained, but this resulted in a smudged discolored pattern. The results obtained by cyanoacrylate fuming and stain alone were of high quality and not in need of further enhancement by the other treatments in the sequence (Figure 9).

Overall

Table 1 outlines the techniques that were investigated in this study and shows some of their characteristics that should be considered when approaching latent fingermark development on the adhesive side of black electrical tape.

The recommended sequence for use as a standard operating procedure is cyanoacrylate fuming and application of BY40/BR28 combined fluorescent stain, followed by the white powder suspension prepared and applied using the suggested formulation. The final stage is the application of gentian violet solution, containing phenol and ethanol, followed by transfer to photographic paper.

Conclusions

The formulated white powder suspension developed latent fingermarks on the adhesive side of the tapes that were comparable to those obtained using the traditional method of cyanoacrylate fuming and staining. These two methods were found to be far superior to the silver powder suspension and the Ardrox formulation. The quality of the detail, contrast, and sharpness in developed marks was consistently of a higher standard for cyanoacrylate and the white powder suspension. This held true for both fresh marks and marks that were 35 days old. The evaluation of techniques requiring a transfer to photographic paper showed that gentian violet was superior to the black powder suspension, sticky-side powder, and small were easily transferred and showed detail and contrast of high quality.

Table 1

The most effective formulation for the white powder suspension was established and found to be suitable for developing latent marks on the adhesive side of black electrical tape. This suspension contained both Photo-Flo and Citron detergent, and was superior to using detergent or Photo-Flo alone in the formulation. This suspension consistently developed latent marks on the adhesive side of all five tapes, showing detail, contrast, and sharpness superior to the characteristics observed in the marks treated with the other formulations tested. It is the recommended formulation for a white powder suspension to treat the adhesive side of black electrical tape.

A practical sequence was developed to allow for maximum development and the greatest enhancement of any latent marks, without causing the destruction of the deposits for subsequent methods. This sequence included three stages: cyanoacrylate fuming plus staining, followed by treatment with the white powder suspension, and, if necessary, processing with gentian violet and transferring to photographic paper. The entire sequence could be applied to the adhesive side if required, and the first stage (cyanoacrylate fuming plus staining) can also be used on the backing (Figure 10).

For further information, please contact:


Claude Roux, Ph.D.
Center for Forensic Science
University of Technology Sydney
PO Box 123
Broadway NSW
2007 Australia
+61 2 9514 1718
claude.roux@uts.edu.au
www.forensics.edu.au

References

1. Burns, D. S. Sticky-side Powder: The Japanese Solution. J. For. Ident. 1994, 44 (2), 133-138.
   
   
2. Sneddon, N. Black Powder Method to Process Duct Tape. J.For. Ident. 1999, 49 (4) 347-356.
   
   
3. Martin, B. L. Developing Latent Prints on the Adhesive Surface of Black Electrical Tape. J. For. Ident. 1999, 49 (2), 127-129.
   
   
4. Parisi, K. M. Getting the Most from Fingerprint Powders. J. For. Ident. 1999, 49 (5), 494-498.
   
   
5. Wade, D. C. Development of Latent Prints with Titanium Dioxide (TiO). J. For. Ident. 2002, 52 (5), 551-559.
   
   
6. Rees, A. S.; Schwartz, R. L. The Effectiveness of Liqui-Drox and a Comparison to Other Adhesive-Side Processes on a Variety of Tapes. For. Sci. Comm. 2003, 5 (1).
   
   
7. Stoilovic, M.; Lennard, C. The Application of Light in Forensic Science and A Modern Approach to Fingerprint Detection and Enhancement, Australian Federal Police Workshop Manual. October 2000.
   
   
8. Bratton, R.; Gregus, J. Development of a Black Powder Method to Process Adhesive Tapes. Fingerprint Whorld 1996, 12 (2), 6.

Figure 1
"PVC" tape showing cyanoacrylate-developed marks, followed
by rhodamine 6G stain (a) and BY40/BR28 stain (b). Images are
inversed and photographed in the fluorescence mode.

Figure 2
Strong (a), medium (b), and weak (c) marks on "PVC" tape
developed by cyanoacrylate fuming and stained with BY40/BR28,
visualized in the fluorescence mode. Images are inversed.

Figure 3
White powder suspension for fresh marks (a) and aged marks (b)
on "PVC" tape. Images are inversed.

Figure 4
"Huskeytape" showing fresh marks treated with white powder
suspension (left) and silver powder suspension (right). Image is inversed.

Figure 5
Comparison of sticky-side powder (left) with black powder
suspension (right) on fresh marks after transfer from "Nitto" tape.

6a

6b

Figure 6
Latent marks on "PVC" tape treated with cyanoacrylate followed by white
powder (a), compared to white powder alone (b). Images are inversed.

7a

7b

Figure 7
BY40/BR28 staining after cyanoacrylate on "PVC" tape (a)
followed by white powder suspension (b). Images are inversed.

8a

8b

8b

Figure 8
Sequence applied to fresh prints on "Huskeytape",
showing cyanoacrylate plus stain (a), white powder (b),
and gentian violet transfer (c).

Figure 9
Week-old latent marks on the backing of "PVC" tape developed
by cyanoacrylate and stained with BY40/BR28.

Figure 10
Recommended sequence for latent fingermark detection
on black electrical tape.

*From the Journal of Forensic Identification Vol. 55, No. 2, March/April 2005
The Official Publication of the International Association for Identification
"Reproduction of the Journal of Forensic Identification, in whole or in part, for noncommercial, educational use is permitted provided proper citation of the source is noted. Reproduction for any other use is prohibited without prior written permission. Requests for permission may be addressed to the editor (of the Journal of Forensic Identification -- jfieditor@theiai.org)."