Analytical Science and Technology (분석과학)

The Korean Society of Analytical Sciences (한국분석과학회)
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Development of latent fingerprints contaminated with ethanol on paper surfaces

  • Park, Eun-Jung (Graduate School of Forensic Science, Soonchunhyang University) ;
  • Hong, Sungwook (Graduate School of Forensic Science, Soonchunhyang University)
  • Received : 2019.04.23
  • Accepted : 2019.05.31
  • Published : 2019.06.25
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Abstract

Fingerprints may be contaminated with ethanol solutions. In order to solve the case, the law enforcement agency may need to visualize the fingerprint from these samples, but the development method has not been studied. The paper with latent fingerprint was contaminated with ethanol solution and then the blurring of ridge detail was observed. As a result, when the copy paper was contaminated with ethanol solutions of less than 75 % (v/v), the amino acid components of latent fingerprint residue blurred but lipid components of latent fingerprint residue didn't blurred. On the other hand, when the paper was contaminated with ethanol solution of more than 80 % (v/v), the amino acid components of latent fingerprint didn't blurred but the lipid components of latent fingerprint blurred. Therefore, it is found that the paper contaminated with ethanol solutions of less than 75 % (v/v) should be treated by oil red O (ORO) enhancing lipid components, and the paper contaminated with ethanol solutions of 80 % (v/v) or more should be treated by 1,2-indandione/zinc (1,2-IND/Zn) enhancing amino acid components. The blurring of ridge detail was not observed when the fingerprints were deposited with fingers contaminated with ethanol solution. This fingerprints were treated with 1,2-IND/Zn or ORO to compare the latent fingerprint development ability, and using 1,2-IND/Zn was able to visualize the latent fingerprint more clearly than using ORO.

Keywords

1. Introduction

Fingerprints play a crucial role in solving crimes.1However, most fingerprints left at a crime scene arelatent fingerprints that are not visible to the nakedeye without a fingerprint developing process.2 Thus, latent fingerprints must be appropriately developed to be visible to the naked eye in order to use them to identify a victim or suspect, or to compare with otherfingerprints. 1 For this reason, developing latent fingerprints is a critical process in forensic science, and numerous forensic scientists have researched optical, 3,4 physical,5,6 and chemical7,8 methods fordeveloping latent fingerprints. As a result, it has been found that different methods of development must be used depending on the components of the fingerprint residue and the surface upon which the fingerprint is deposited.9

Considering fingerprints residue components on a porous surface such as paper, moisture evaporates over time, leaving amino acids, lipids, salts, andurea. Depending on the state of the item (e.g., wet, burned) and fingerprint residue components, aminoacid sensitive reagents and lipid sensitive reagents must be used for selective treatment.10 Latent fingerprints on a porous surface that has never been wet can be developed using ninhydrin,7,11 whichreacts with amino acids, or its analogue 1,2-indandione/zinc (1,2-IND/Zn)12-14 or 1,8-diazafluoren-9-one (DFO).15,16,17 However, if a item with fingerprints is wet with water, the fingerprint cannot be developed with amino acid sensitive reagents because the aminoacid components of the fingerprint are dissolved in water. 9,18,19 In such cases, the latent fingerprint can be developed using a lipid sensitive reagent, becauselipids do not dissolve in water.15 Common reagents for this purpose include oil red O (ORO)8,20,21 and Nile red.19,22

Items upon which latent fingerprints have beendeposited can be contaminated by various liquid sencountered in daily life (e.g., alcoholic drinks, juice, milk, carbonated drinks).23 Among them, ethanol-contaminated fingerprints are likely to be found at crime scenes because ethanol is included in a variety of products, such as alcohol, cleansers, and s anitizers. Contamination of objects with fingerprints by ethanolsolution or touching of an object with ethanol-contaminated hands are such cases. In a study ondeveloping fingerprints deposited on an object and contaminated with ethanol, Cohen et al. (2012), after touching a face and hair, deposited fingerprints on the surface of a polyvinyl chloride (PVC) window shutter and a white powder-coated aluminum window frame. Then, they contaminated the fingerprints with three types of cleaning agents with ethanol content < 5 % (v/v), and treated them with black magnetic powder. They found that fingerprints from the PVC window shutter and aluminum window frame werenot developed, depending on the type of cleaning agent used.23 After touching a face, then depositing a fingerprint on the surface of aluminum foil, conta-minating it with beer and wine, and treating it with black magnetic powder or small particle reagent (SPR), Maslanka (2016) reported that a fingerprinttreated with black magnetic powder was similarly ormore clearly developed than a fingerprint treated with SPR.24 In a study on developing fingerprints deposited by a hand contaminated with ethanolsolution, Chadwick et al. (2017) applied an al cohol-based hand sanitizer on the hands, dried it for 20-30 seconds, deposited fingerprints on copy paper, and developed the fingerprints using 1,2-IND/Zn, ninhydrin, and physical developer (PD). The results showed that fingerprints were most clearly developed with 1,2-IND/Zn.25 However, there has been no report on whether targeting amino acid or lipid components would better develop fingerprints when paper with fingerprints is contaminated with ethanol or is touched with an ethanol-contaminated hand.

Because ethanol consists of both polar and n on polar functional groups, it can dissolve water-solublesubstances such as amino acids26 as well as insolublesubstances such as lipids.27 Fingerprints can becontaminated by alcoholic drinks, mouthwash, and hand sanitizers, as opposed to pure ethanol solution, and in such cases, the properties of dissolving aminoacids or lipids included in the fingerprint residue components would vary due to the water content in the ethanol-containing product. Thus, fingerprints residue components would be washed away differently, and different methods need to be used to develop the fingerprints. However, to the best of our knowledge, there has been no relevant study.

 

2. Materials and Methods

 

2.1. Materials

ORO powder from Alfa Aesar (USA), 1,2-IND powder from 1,2-IND Sirchie (USA), and zincchloride from Merck (Germany) were used. Cass beer (Oriental Brewery, Korea), Chamisul Fresh soju(Hite Jinro, Korea), Garglin Original mouthwash(Dong a Pharmaceuticals, Korea), and Dettol Original hand sanitizer (Dettol, Thailand) were used.

The LS301 scale from Libra (Korea) and SSP-2308 digital steam press from Sienna (USA) were used. A 505-nm light source (Polilight Flare Plus 2 from Rofin, Australia) and orange filter from R of in(Australia) were used. A D3400 camera from Nikon (Japan) was used with a 60 mm f/2.8 2X UltraMacro lens from Laowa (China).

 

2.2. Fingerprint

Latent fingerprints were deposited by men and women in their 20s by pressing down their right thumbs for 5 seconds such that the needle of the scale pointed to 500 ± 100 g. Three types of latent fingerprints were prepared: eccrine gland secretionfingerprints, sebaceous gland secretion fingerprints, and natural fingerprints. The eccrine gland secretionfingerprints were prepared by having fingerprintdonors wash hands with soap and water and wearplastic gloves for 30 minutes to secrete sweat beforedepositing a fingerprint with the right thumb. These baceous gland secretion fingerprints were prepared by having donors wash hands with soap and waterand rub their noses with their right thumbs threetimes before depositing a fingerprint. The natural fingerprints were prepared by having donors depositfingerprints after 30 minutes of free activity without washing hands.

2.3. Methods

Zinc chloride stock solution was prepared by dissolving 0.4 g of zinc chloride in 10 mL of ethanoland adding 1 mL of ethyl acetate and 190 mL of petroleum ether. The 1,2-IND/Zn solution was prepared by adding 80 mL of zinc chloride stock solution to asolution containing 0.8 g of completely dissolved 1,2-IND in 90 mL of ethyl acetate and 20 mL ofacetic acid; then adding 820 mL of petroleum ether.28 Fingerprints were developed by dipping them in the 1,2-IND/Zn solution for 5 seconds, completely drying them, and then applying heat for 10 seconds at 180 ℃ using a digital steam press.

The ORO solution was prepared by mixing asolution containing 9.2 g of sodium hydroxide dissolved in 230 mL of deionized water, with a solution containing 1.54 g of ORO powder dissolved in 770 mL of methanol, and then filtering the mixture. The washing buffer solution was prepared by dissolving 26.5 g of sodium carbonate in 2000 mL of deionized water, adding 18.3 mL of concentrated nitric acid, and then adding deionized water to the 2500 mL mark.28 When staining with ORO, the fingerprint was dipped in the ORO solution for 5 minutes, taken out, and washed with the buffer solution. Allexperiments were performed in a laboratory with temperature and relative humidity maintained at 21 ± 10 °C and 50 ± 20%, respectively.

 

3. Results and Discussion

There are two ways by which paper at a crimescene could be contaminated with ethanol solution. The fingerprint could be contaminated with ethanolsolution after being deposited, or the fingerprint could be deposited by a hand already contaminated with ethanol. Therefore, both cases were examined in this study.

 

3.1. Development of latent fingerprint conta-minated with ethanol solution after deposition on paper

After depositing an eccrine gland secretion fingerprintor sebaceous gland secretion fingerprint on copy paper, it was contaminated with ethanol solution by submerging it in 0-100 % (v/v) ethanol solution for 5 seconds and then taken out and dired for 1 day. The eccrine gland secretion fingerprints were developed with 1,2-IND/Zn and sebaceous gland secretionfingerprints were developed with ORO. The results are shown in Fig. 1. The eccrine gland secretionfingerprint in Fig. 1 shows that the ridges are severely blurred when exposed to a low-concentration ethanolsolution, but the ridge blurring decreased withexposure to more concentrated ethanol solutions. A fingerprint with good ridge detail is shown when it was exposed to a high-concentration of ethanolsolution (≥ 80 % v/v). On the other hand, for these baceous gland secretion fingerprints, the ridges werenot blurred and developed well when contaminated with ethanol solution of ≤ 75 % (v/v), but the ridges blurred and fingerprints could not be developed when the sample was contaminated with an ethanol concentration of ≥ 80 % (v/v). These results seem to have resulted from the fact that, as the ethanol concentration decreases, the fraction of water contentin the solution increases, thereby washing away moreamino acid components and less lipid components, and vice versa.

 

BGHHBN_2019_v32n3_105_f0001.png 이미지

Fig. 1. The blurring of the eccrine and sebaceous gland secretion fingerprints contaminated with ethanol solutions (The numbers shown in the figure are the % (v/v) concentration of the ethanol solution that contaminated the fingerprint). Top: Eccrine gland secretion fingerprint treated with 1,2-IND/Zn. Bottom: Sebaceous gland secretion fingerprint treated with ORO.

These results show that ORO should be used whencopy paper with fingerprints is contaminated withe thanol solution of ≤ 75 % (v/v) and 1,2-IND Znshould be used when contaminated with ethanolsolution of ≥ 80 % (v/v) in order to develop latent fingerprints with good ridge detail. To confirm this, natural fingerprints contaminated with ethanol solution with a concentration of 0-100 % (v/v) were split into two fragments. One fragment was treated with 1,2-IND/Zn while the other was treated with ORO. Theresults are shown in Fig. 2. As predicted, using ORO for latent fingerprints contaminated with ethanolsolution with a concentration of ≤ 75 % (v/v) and using 1,2-IND/Zn for those contaminated with ethanolsolution with a concentration of ≥ 80 % (v/v) best developed the fingerprints and provided good ridge detail.

 

BGHHBN_2019_v32n3_105_f0002.png 이미지

Fig. 2. The blurring of the natural fingerprints contaminated with ethanol solutions. Left: Fingerprint treated with 1,2-IND/ Zn. Right: Fingerprint treated with ORO.

The above results were obtained using pure ethanolsolutions. However, ethanol-containing products on the market, such as beer, soju, mouthwash, and handsanitizers, are not pure ethanol solutions. Therefore, actual items contaminated with such products should be tested in order for our results to be applied to real cases. Fig. 3 shows the results of contaminatingnatural fingerprints using products with varying ethanol concentrations (≤ 75 % v/v), including beer (4.5 % v/v), soju (17.2 % v/v), mouthwash (8 % v/v), and handsanitizer (60-75 % v/v). Each of these was split into two fragments, one of which was treated with 1,2-IND/Zn and the other with ORO. As predicted, natural fingerprints contaminated with beer, soju, mouthwash, and hand sanitizer developed well without ridge blurring when treated with ORO, but the fingerprints were not developed well when treated with 1,2-IND/Zn. This shows that ORO can be used to developfingerprints even when contaminated with solutionsother than pure ethanol. Most market products withe thanol (e.g., alcoholic drinks, mouthwash, handsanitizer) have ethanol content < 80 % (v/v). Therefore, when developing latent fingerprints exposed to market products with ethanol, reagents that enhance lipid components, such as ORO, should be used.

 

BGHHBN_2019_v32n3_105_f0003.png 이미지

Fig. 3. The blurring of the natural fingerprints contaminated with beer, soju, mouthwash and hand sanitizer. Left: Fingerprint treated with 1,2-IND/Zn. Right: Fingerprint treated with ORO.

The 1,2-IND/Zn working solution consists of ethanol, ethyl acetate, petroleum ether, and acetic acid, whereasthe ORO working solution consists of water and methanol. Water in the working solution can dissolveamino acids while organic solvents can dissolve lipid components. This means that it is impossible to re-treat with ORO after first treating with 1,2-IND/Zn or viceversa. Thus, when attempting to develop fingerprints from ethanol-contaminated paper, they need to choose between 1,2-IND/Zn and ORO. Investigators do not know whether the ethanol-contaminated item they are investigating has been exposed to an ethanolsolution with a concentration of < 80 % (v/v) or ≥ 80 % (v/v). Nearly all ethanol solutions on the market have a concentration of < 80 % (v/v), andethanol solutions with concentration of ≥ 80 % (v/v) areavailable only in special environments, such aschemical laboratories or chemical plants. Thus, ORO is recommended when treating fingerprints contaminated with ethanol at a general crime scene outside achemical laboratory or chemical plant.

 

3.2. Development of latent fingerprints deposited on paper with finger contaminated with ethanol solution

Immediately prior to depositing an eccrine gland secretion fingerprint or sebaceous gland secretionfingerprint, 1 mL of ethanol solution of varying concentrations (0-100 % v/v) was dripped onto the thumb, and the donors were asked to rub their thumbwith their index and middle fingers to apply the ethanol solution evenly over the finger surfaces. Then the thumb was used to deposit a fingerprint oncopy paper. Next, eccrine gland secretion fingerprints were treated with 1,2-IND/Zn, and sebaceous gland secretion fingerprints were treated with ORO. Theresults are shown in Fig. 4, in which good ridge details are achieved for both eccrine gland secretionfingerprints and sebaceous gland secretion fingerprints when the fingerprints were deposited by a fingercontaminated with ethanol solution with a concentration of 0-100 % (v/v).

 

BGHHBN_2019_v32n3_105_f0004.png 이미지

Fig. 4. Blurring of the fingerprints deposited with fingers contaminated with 0 % (v/v) and 100 % (v/v) ethanol. Top: Eccrine gland secretion fingerprint treated with 1,2-IND/Zn. Bottom: Sebaceous gland secretion fingerprint treated with ORO.

These results show that ethanol concentration does not affect fingerprint ridges when depositing fingerprints with ethanol-contaminated fingers. To confirm this, the thumb was contaminated with ethanol solution (0-100 % v/v) immediately prior to depositing anatural fingerprint on copy paper, and the deposited fingerprint was split into two fragments to treat one fragment with 1,2-IND/Zn and the other with ORO.

As shown in Fig. 5, there was no ridge blurring in eithercase despite the fact that the fingerprints were deposited using fingers contaminated with ethanolsolution of 0-100 % (v/v). Treatment with 1,2-IND/Zn led to more developed fingerprints than did treatment with ORO. These results seem to be due to the fact that sweat contains an abundance of aminoacids,29 and that 1,2-IND/Zn reacts with amino acids to generate strong fluorescence.30

 

BGHHBN_2019_v32n3_105_f0005.png 이미지

Fig. 5. Blurring of the fingerprints deposited with fingers contaminated with 0 % (v/v) and 100 % (v/v) ethanol. Left: Fingerprint treated with 1,2-IND/Zn. Right: Fingerprint treated with ORO.

These results were obtained by contaminating the finger with pure ethanol solution. However, ethanol-containing products on the market, such as beer, soju, mouthwash, and hand sanitizers, are not pureethanol solutions, so actual items contaminated with such products should be tested in order for our results to be applied to actual crime cases. Fig. 6 shows the results of splitting natural fingerprints contaminated with varying ethanol concentrations (≤ 75 % v/v)using beer (4.5 % v/v), soju (17.2 % v/v), mouthwash(8 % v/v), and hand sanitizer (60-75 % v/v) into twof ragments. One fragment of each pair was treated with 1,2-IND/Zn and the other with ORO. The figureshows that ridge blurring was not observed in any of the natural fingerprints deposited with fingerscontaminated with beer, soju, mouthwash, and handsanitizer. Moreover, 1,2-IND/Zn was more sensitive than ORO to develop latent fingerprints deposited with fingers contaminated with ethanol-containing solutions. Chadwick et al. (2017) reported that 1,2-IND/Zn can be used to develop clear fingerprints leftwith fingers after applying an alcohol-based handsanitizer,25 which is in line with our findings. Ourresults show that 1,2-IND/Zn should be used todevelop latent fingerprints deposited with fingerscontaminated with ethanol-containing solution.

 

BGHHBN_2019_v32n3_105_f0006.png 이미지

Fig. 6. The blurring of the natural fingerprints contaminated with beer, soju, mouthwash and hand sanitizer. Left: Fingerprint treated with 1,2-IND/Zn. Right: Fingerprint treated with ORO.

 

4. Conclusions

In this study, the development of latent fingerprints on copy paper contaminated with 0-100 % (v/v) ethanol solution was attempted with 1,2-indandione/zinc (1,2-IND/Zn) or oil red O (ORO). The results showed that fingerprints were successfully developed using ORO for those contaminated with a concentration of of ≤ 75 % (v/v) ethanol and better developed using1,2-IND/Zn for those contaminated with a concentration ≥ 80 % (v/v). Latent fingerprints deposited on copy paper that were contaminated with ethanol of ≤ 75 % (v/v) from commercial products such as beer, soju, mouthwash, and hand sanitizer were developed with better ridge detail when treated with ORO ratherthan 1,2-IND/Zn.

We also treated fingerprints deposited on copy paper by fingers contaminated with 0-100 % (v/v) ethanol with 1,2-IND/Zn or ORO and found that these fingerprints should be developed with 1,2-IND/Zn. Latent fingerprints deposited on copy paperwith fingers contaminated with beer, soju, mouthwash, or hand sanitizer were developed with bettersensitivity when treated with 1,2-IND/Zn compared to ORO.

 

Acknowledgements

This research was supported by Projects for Researchand Development of Police science and Technology under Center for Research and Development of Police science and Technology and Korean National Police Agency (PA-B000001).

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