To assess the significance levels between the DNA yields

The data were log10 transformed in order to improve the normality of variables. AWilcoxon Signed Rank test was performed in order to assess the significance levels between the DNA yields

Fig. 1. Schematic of touch DNA collection techniques. This schematic illustrates the techniques (A) water-soluble tape lifting or double swabbing and (B) FTA paper scraping or double swabbing that were used to collect touch DNA from the surface of the steering wheels.

I.A. Kirgiz, C. Calloway / Journal of Forensic and Legal Medicine 47 (2017) 9e15 11

from the touch DNA collection techniques. Statistical analysis was performed using JMP software (SAS Institute, North Carolina).

3. Results

Detectable quantities of touch DNAwere recovered from each of the 70 steering wheels sampled, independent of collection method and randomized for collecting from the right or the left side for a total of 140 samples (Fig. 2A and B, Supplemental Tables 1A and 1B). However, the DNA yield was dependent on the DNA collection method. The mean DNA yield was two-fold higher for the double swabbing method compared to tape lifting (16.1 vs. 7.37 ng). The standard deviation was also higher for the double swabbing method, 27.6 vs. 16.5. However, the median DNA yield was only slightly higher for the double swabbing method than for the tape lifting (2.46 vs. 2.05 ng). DNA yields from 50% of the samples (samples in the interval between the 25% and 75%) collected using the double swabbing technique fell within the range of 0.87 nge26.6 ng; 50% of tape lifting samples fell within the range of 1.22 nge4.88 ng (Fig. 2A). AWilcoxon Signed Rank test was used on the log10 transformed data to determine if the differences in the DNA yield between swabbing versus tape lifting were statistically significant and no significant difference in the yield was observed (p ¼ 0.21) (Fig. 3A).

For the double swabbing versus FTA paper scraping comparison, touch DNA was collected from 35 steering wheels using either method, randomized for collecting from the right or the left side for a total of 70 samples (Fig. 2B). Samples collected from one steering wheel, which yielded 884 ng using the double swabbing method (26 fold higher than the next highest sample) and 114 ng DNA using FTA paper (7 fold higher than the next highest sample), was considered an outlier and was removed from the dataset. The mean DNA yields were similar using the FTA scraping method compared to the double swabbing (5.33 vs. 5.22). However, the median value was two-fold higher for the FTA scraping method (4.78) compared to double swabbing (2.26). DNA yields from 50% of the double swabbing samples (samples in the interval between the 25% and 75%) fell within 0.62 nge4.36 ng range; and 50% of FTA scraping samples fell within 1.89 nge7.89 ng range (Fig. 2B). A statistically significant difference in DNA yield between the FTA scraping and the double swabbing methods was observed using a Wilcoxon Signed Rank test on the log10 transformed data (p ¼ 0.0051) with

the FTA paper scraping method yielding higher amounts of touch DNA (Fig. 3B).

3.1. STR results

Based on the DNA concentration yield, a majority of the samples collected using double swabbing (55%) or tape (60%) would be expected to result in partial or no STR profile using standard STR kits which recommend 0.5 ngs of DNA (�0.05 ng/mL) compared to 35% of the samples collected using FTA paper (Fig. 2). Also, almost 50% of the samples collected using FTA paper (18 out of 34) yielded DNA concentrations high enough to allow for 1 ng DNA input for STR analysis compared to 30% for double swabbing and 23% for tape lifting. A subset of these higher yield samples were selected for STR analysis based on the DNA amount (>1 ng) to confirm that the DNA collected from the steering wheel was from the driver.

For the double swabbing versus tape lifting comparison, the mean % STR allele recovery of the driver was higher for double swabbing (91%) when compared to tape lifting (59%) (Fig. 4A). For the double swabbing versus FTA paper scraping comparison, the mean % STR allele recovery of the DNA was slightly higher for double swabbing (99%) than for FTA paper scraping (91%) (Fig. 4B). A full STR profile was observed for 21 out of the 32 samples (66%); four of the 21 full profiles were from a single source. No profile was generated for two of the 32 samples and both samples were collected using tape. The STR failure of these two samples is not likely due to PCR inhibition since the same tape brand was used for this study as a studywhich showed that the tape did not inhibit PCR even with increased lengths of tape.11

Nine samples (28%) yielded only partial profiles and five of these samples generated searchable partial profiles (containing STR al- leles at � ten CODIS Core Loci). A mixed STR profile containing two or more contributors was observed for 26 samples or 88%. For all cars sampled, the primary driver was the last driver and for 29 samples out of 32, the driver was also the major DNA contributor. For one car sampled, the last driver was not the major contributor (Supplementary Tables 2A and 2B).

4. Discussion

The results of the study show that each of the three DNA collection methods was able to recover detectable quantities of

Swab (N =35)

Tape (N =35)DNA Collection Methods

Swab N =34

FTA N =34 DNA Collection Methods

)gn( stnuo

m A

A N

Fig. 2. The amount of touch DNA collected. DNA was collected from one side of a steering wheel using (A) the double swabbing or tape lifting method or (B) double swabbing or FTA paper scrapping method and quantified in duplicate using qPCR. The total DNA amounts (ng) recovered from each steering wheel were plotted on a log scale. 50% of the data is located within the rectangles; the whiskers cover 90% of the data. The median is indicated by the solid line.

I.A. Kirgiz, C. Calloway / Journal of Forensic and Legal Medicine 47 (2017) 9e1512

P=0.21

P=0.0051

ecnereffi D

(L og

10 Ta

pe –

Lo g 1

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wS ecnereffi

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Fig. 3. Matched Pair Difference, Wilcoxon Signed Rank Test. The graph shows the difference of the log10 transformed amount of the touch DNA collected by (A) tape lifting method and double swabbing method; (B) FTA scraping method and by double swabbing method. Wilcoxon Signed Rank test was used to determine if there were significant differences in yield for paired samples collected from different sides of the same steering wheel (A) p ¼ 0.21; (B) p ¼ 0.0051. The dark solid line represents the overall mean difference across the 35 cars.

I.A. Kirgiz, C. Calloway / Journal of Forensic and Legal Medicine 47 (2017) 9e15 13

DNA. However, not all methods were equally effective in collecting touch DNA from the steering wheels. The FTA paper scraping method was shown to yield significantly more DNA from steering wheels compared to double swabbing while no significant differ- ence was observed between double swabbing and tape lifting. DNA yields obtained from the double swabbing collection method were most highly dispersed (10,000 fold difference from lowest to highest). This higher variability in DNA yield across steering wheels using the double swabbing method may result from less efficient collection of the DNA or loss of DNA during extraction from the cotton swab.

Touch DNA yields collected by tape lifting were not as widely dispersedwhen compared to double swabbing. One explanation for the smaller range could be that the tape becomes saturated with materials, therefore reducing its ability to collect touch DNA. Also, tape attachment properties (stickiness) decreased when used over

a large surface area, therefore it was important to start the tape lifting collection at the region with the highest expected DNA concentration. Since there is great variability for the hand position of the driver, it may not always be possible to correctly estimate areas where the steering wheel was primarily handled. Due to a large surface area, the tape was able to cover the entire steering wheel. During the collection process the tape needs to be handled with caution as it can stick to itself or to other surfaces. Further, when the water soluble tape was dissolved in water, it formed a viscous mass that had a hard time passing through the QIAamp silica membrane. Even though that obstacle was overcome by increasing the centrifugation time, the amount of tape that could be processed for a particular sample was limited.

The FTA paper scraping method yielded significantly more DNA collected from the surface of a steering wheel when compared to double swabbing. One possible explanation for the higher DNA

Fig. 4. % STR Allele Recovery of Last Driver’s Profile. The figure compares the percent of STR peaks recovered from the last driver’s profile for eight cars. Touch DNA collection methods are compared based on how well they recovered the last driver’s profile. (A) Recovery mean: double swabbing 91%; tape lifting 59%. Paired T-test: p ¼ 0.10. (B) Recovery mean: double swabbing 99%; FTA paper scraping 91%. Paired T-test: p ¼ 0.29. The results for both studies are not statistically significant.

I.A. Kirgiz, C. Calloway / Journal of Forensic and Legal Medicine 47 (2017) 9e1514

yields could be that the chemical composition of the FTA paper allows for greater preservation and release of the DNA20 in com- parison to the cotton swab which can trap DNA in the fibers.9 Also, FTA paper has a greater surface area when compared to swabs and could therefore cover a larger area, potentially resulting in higher collection yields.3 The cotton swab has a relatively small surface area compared to FTA paper and tape, and therefore, the collection process was longer for double swabbing in comparison. The FTA paper did not dry as fast as swabs and still appeared wet at the end of the collection process. One limitation of the FTA paper was that in some cases scraping the wet paper across a rough surface resulted in the loss of some of the paper fibers. In the future, less water could be applied to the paper. Alternatively, the filter paper could be replaced by a sturdier matrix to minimize tearing and potential DNA sample loss.

Our results demonstrate that in some cases there is enough touch DNA on the steeringwheel of vehicles to yield a complete STR

profile of the last driver. We observed that steering wheels retain DNA of the recent driver even if vehicles were driven for a short period of time (as short as 2min, data not shown). However, as may be expected, a majority of the samples collected from steering wheels resulted inmixed STR profiles. Based on DNA concentration, DNA collected from steering wheels using FTA paper was more likely to result in a more complete STR profile compared to swab- bing or tape lifting as ~50% of the samples yielded concentrations high enough to allow for 1 ng input using FTA paper compared to 20e30%.

Touch DNA collected from a steering wheel is a powerful tool for solving crimes. The FTA paper scraping method has the potential to be used to recover touch DNA from the steering wheels of vehicles and similar objects for increased DNA yields. This novel method could be particular useful in situations when the exact location of touch DNA is unknown or small quantities of touch DNA are dispersed over a large surface. Additional studies are needed to

I.A. Kirgiz, C. Calloway / Journal of Forensic and Legal Medicine 47 (2017) 9e15 15

further evaluate the use of FTA paper as alternative touch DNA collection method or use in combination with other standard methods such as double swabbing.

Conflict of interest

The authors Irina Kirgiz and Cassandra Calloway have no financial or other conflict of interest to report.

Acknowledgements

This researchwas supported and funded by a research fund from the University of California, Davis Forensic Science Graduate Pro- gram. We would like to thank Cecilia VonBeroldingen and Robert Rice for their critical review of the study proposal. We would also like to thank Cecilia VonBeroldingen and George Sensabaugh for their critical review of the manuscript.

Appendix A. Supplementary data

Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jflm.2017.01.007.

References

1. Motor Vehicle Theft. The Federal Bureau of Investigation. vol. 1. Jan. 2012. Web. 10 Jan. 2015 http://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2012/ crime-in-the-u.s.-2012/property-crime/motor-vehicle-theft/mvtheftmain.pdf.

2. Analytical report motor vehicle crime in global perspective. Interpol. Jan 2014;24.

3. Williamson AL. Touch DNA: forensic collection and application to in- vestigations. J Assoc Crime Scene Reconstr. 2012;18:1e5.

4. van Oorschot RAH, Jones MK. DNA fingerprints from fingerprints. Nature.

1997;387:767. 5. Minor Joe. Touch DNA: from the crime scene to the crime laboratory. Forensic

Mag. April/May 2013. 6. Van Oorschot RAH, Weston R, Jones MK. Retrieval of DNA from touched objects.

Proceedings of the 14th International Symposium on the Forensic Sciences of Australian and New Zealand Forensic Science Society, Oct 12-16, 1998.

7. Verdona Timothy J, John Mitchell R, van Oorschot Roland AH. Evaluation of tapelifting as a collection method for touch DNA. Forensic Sci Int Genet. 2014;8: 179e186.

8. Sweet D, Lorente M, Lorente JA, Valenzuela A, Villanueva E. An improved method to recover saliva from human skin: the double swab technique. J Forensic Sci. 1997 Mar;42:320e322.

9. Van Oorschot RAH, Phelan DG, Furlong S, Scarfo GM, Holding NL, Cummins MJ. Are you collecting all the available DNA from touched objects? Int Congr Ser. 2003;1239:803e807. http://dx.doi.org/10.1016/S0531-5131(02)00498-3.

10. Kobilinsky L, Liotti TF, Oeser-Sweat J. DNA: Forensic and Legal Applications. Hoboken (NJ): Wiley; 2004:45e148 (Chapter 3), Forensic DNA Analysis Methods.

11. Li Richard C, Harris Howard A. Using hydrophilic adhesive tape for collection of evidence for forensic DNA analysis. J Forensic Sci. November 2003;48.

12. Van Oorschot RA, Ballantyne KN, Mitchell RJ. Forensic trace DNA: a review. Investig Genet. 2010;1:14. http://dx.doi.org/10.1186/2041-2223-1-14.

13. FTA™ Cards. Collect, Archive, Transport, and Purify Nucleic Acids All at Room Temperature. vol. 1. GE Healthcare; Feb. 2010. Web. 17 Feb. 2014 https:// promo.gelifesciences.com/gl/RAPID-DNA/misc/Whatman-FTA-cards-data-file. pdf.

14. Pizzamiglio M, Mameli A, My D, Garofano L. Forensic identification of a murderer by LCN DNA collected from the inside of the victim’s car. Int Congr Ser. 2004;1261:437e439.

15. Hansson O, Finnebraaten M, Heitmann IK, Ramse M, Bouzga M. Trace DNA collection e performance of minitape and three different swabs. Forensic Sci Int Genet Suppl S. 2009;2(1):189e190.

16. Dutelle Aric W. Crime Scene Investigation: A Guide for Law Enforcement. third ed. Burlington, MA: Jones & Bartlett Learning; 2016:512.

17. Qiagen. QIAamp DNA Investigator Handbook. Hilden Germany: Qiagen; 2007. 18. Promega. Plexor® HY System Technical Manuals. Madison, WI: Promega; 2013. 19. Applied Biosystems. AmpFISTER® Identifiler® PCR Amplification Kit User Guide.

Foster City, CA: Applied Biosystems; 2012. 20. Milne E. Buccal DNA collection: comparison of buccal swabs with FTA cards.

Increased recovery of touch DNA evidence using FTA paper compared to conventional collection methods
- 1. Introduction
- 2. Materials and methods
  - 2.1. DNA collection
  - 2.2. DNA extraction and analysis
  - 2.3. Statistical analysis of data
- 3. Results
  - 3.1. STR results
- 4. Discussion
- Conflict of interest
- Acknowledgements
- Appendix A. Supplementary data
- References

To assess the significance levels between the DNA yields

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