The Use of Adhesive Tape for Recovery of DNA from Crime Scene Items

Abstract: The selection of the appropriate method of collection of biological material from crime scene items can be crucial to obtaining a DNA profile. The three techniques commonly used for sampling items are: cutting, swabbing, and taping. The tape sampling technique offers an advantage, in that it enables the collection of a potentially highly informative source of DNA, shed epithelial cells, from selected areas on crime scene items (the inside fingers of a glove, for instance). Furthermore, surface collection of biological material by taping reduces co‐sampling of known PCR inhibitors such as clothing dyes. The correct choice of tape for crime scene item sampling is important. Not all tapes are suitable for biological trace evidence collection as well as DNA extraction. We report on one tape that met both these criteria. Three different cases are presented which demonstrate the usefulness of adhesive tape sampling of crime items. Finally, the advantages of the tape collection technique are discussed and guidelines for preferred areas of tape sampling on various casework items are presented.     

Collecting touch DNA from glass surfaces using different sampling solutions and volumes: Immediate and storage effects on genetic STR analysis

Touch DNA has become increasingly important evidence in todays' forensic casework. However, due to its invisible nature and typically minute amounts of DNA, the collection of biological material from touched objects remains a particular challenge that underscores the importance of the best collection methods for maximum recovery efficiency. So far, swabs moistened with water are often utilized in forensic crime scene investigations for touch DNA sampling, even though an aqueous solution provokes osmosis, endangering the cell's integrity. The aim of the research presented here was to systematically determine whether DNA recovery from touched glass items can be significantly increased by varying swabbing solutions and volumes compared with water-moistened swabs and dry swabbing. A second objective was to investigate the possible effects of storage of swab solutions prior to genetic analysis on DNA yield and profile quality when stored for 3 and 12 months, as is often the case with crime scene samples. Overall, the results indicate that adapting volumes of the sampling solutions had no significant effect on DNA yield, while the detergent-based solutions performed better than water and dry removal, with the SDS reagent yielding statistically significant results. Further, stored samples showed an increase in degradation indices for all solutions tested, but no deterioration in DNA content and profile quality, allowing for unrestricted processing of touch DNA samples stored for at least 12 months. One further finding was a strong intraindividual change in DNA amounts observed over the 23 deposition days which may be related to the donor's menstrual cycle.     

The Influence of Swabbing Solutions on DNA Recovery from Touch Samples,

There has been minimal research into how to best obtain DNA from touch samples. Many forensic laboratories simply moisten a swab with water and use it for collecting cells/DNA from evidentiary samples. However, this and other methods have not been objectively studied in order to maximize DNA yields. In this study, fingerprints were collected using swabs moistened with water or laboratory or commercially available detergents, including sodium dodecyl sulfate (SDS), Triton X‐100, Tween 20, Formula 409^®, and Simple Green^®. Prints were swabbed, DNA isolated using an organic extraction, yields quantified, and relative yields compared. In all cases, the detergent‐based swabbing solutions outperformed water, with SDS and Triton X‐100 producing significant increases in yield. Short tandem repeat profiles were consistent with the individuals that placed them. Subsequent analysis of SDS concentrations for collecting touch DNA demonstrated an increase in DNA yield with increasing SDS concentration, with an optimal concentration of approximately 2%.     

Firearms discharge residue sample collection techniques.

Critical comparisons of Ba and Sb in firearms discharge residue were made on samples collected by three independent collection technqiues. Collection materials studied were transparent adhesive tape, (Scotch Brand), a solution of cellulose acetate in acetone ("Film Lift"), and plastic-shafted cotton swabs wetted with dilute nitric acid. Flameless atomic absorption analyses were performed with a Jarrell-Ash Model 810 instrument equipped with a tantalum strip atomizer. Tape and cotton swabs gave comparable positive indications of residue, with frequencies of 90 and 80%, respectively. The plastic Film Lift gave fewer positives, with a frequency of 50%. With the transparent tape lift, gunshot residue particles are discernible, making nondestructive microscopic identification possible prior to destructive elemental analysis.     

The use of the M-Vac® wet-vacuum system as a method for DNA recovery

Collecting sufficient template DNA from a crime scene sample is often challenging, especially with low quantity samples such as touch DNA (tDNA). Traditional DNA collection methods such as double swabbing have limitations, in particular when used on certain substrates which can be found at crime scenes, thus a better collection method is advantageous. Here, the effectiveness of the M-Vac® Wet-Vacuum System is evaluated as a method for DNA recovery on tiles and bricks. It was found that the M-Vac® recovered 75% more DNA than double swabbing on bricks. However, double swabbing collected significantly more DNA than the M-Vac® on tiles. Additionally, it was found that cell-free DNA is lost in the filtration step of M-Vac® collection. In terms of peak height and number of true alleles detected, no significant difference was found between the DNA profiles obtained through M-Vac® collection versus double swabbing of tDNA depositions from 12 volunteers on bricks. The results demonstrate that the M-Vac® has potential for DNA collection from porous surfaces such as bricks, but that alterations to the filter apparatus would be beneficial to increase the amount of genetic material collected for subsequent DNA profiling. These results are anticipated to be a starting point to validate the M-Vac® as a DNA collection device, providing an alternative method when DNA is present on a difficult substrate, or if traditional DNA collection methods have failed.     

Recovery of Trace DNA on Clothing: A Comparison of Mini‐tape Lifting and Three Other Forensic Evidence Collection Techniques

Trace DNA is often found in forensic science investigations. Experience has shown that it is difficult to retrieve a DNA profile when trace DNA is collected from clothing. The aim of this study was to compare four different DNA collection techniques on six different types of clothing in order to determine the best trace DNA recovery method. The classical stain recovery technique using a wet cotton swab was tested against dry swabbing, scraping and a new method, referred to as the mini‐tape lifting technique. Physical contact was simulated with three different “perpetrators” on 18 machine‐washed garments. DNA was collected with the four different DNA recovery methods and subjected to standard PCR‐based DNA profiling. The comparison of STR results showed best results for the mini‐tape lifting and scraping methods independent of the type of clothing. The new mini‐tape lifting technique proved to be an easy and reliable DNA collection method for textiles.     

Combined DNA Typing and Protein Identification from Unfired Brass Cartridges,,,

Biological evidence analysis from contact traces is adversely affected by low quantity and quality of DNA. Proteins in these samples contain potentially individualizing information and may be particularly important for difficult surfaces such as brass, where DNA may yield incomplete profiles. In this study, touched unfired brass cartridges were sampled using dry tape or wet swabs and analyzed by separating DNA and protein from the same collected material, thus producing both genomic and proteomic information. DNA recovery was similar for both collection methods, with tape yielding an average of 1.36 ± 1.87 ng and swabs, 1.34 ± 3.04 ng. Analysis by mass spectrometry identified 95 proteins, with the two collection methods showing no significant difference (p = 0.76) in the average number of collected proteins: 44.5 ± 10.9, (tape) versus 47.9 ± 20.4 (swabs). Proteins can be collected from fingerprints at levels necessary to provide identifying information, thus expanding information obtained from challenging evidence.     

Swabs as DNA Collection Devices for Sampling Different Biological Materials from Different Substrates

Currently, there is a variety of swabs for collection of biological evidence from crime scenes, but their comparative efficiency is unknown. Here, we report the results of an investigation into the efficiency of different swab types to collect blood, saliva and touch DNA from a range of substrates. The efficiency of extracting blood and saliva from each swab type was also tested. Some swabs were significantly more effective than others for sampling biological materials from different substrates. Swabs with the highest sampling efficiency, however, often did not have the highest extraction efficiency. Observations were recorded regarding practicality of each swab in a variety of situations. Our study demonstrates that selection of sampling device impacts greatly upon successful collection and extraction of DNA. We present guidelines to assist in evaluation of swab choice.     

Evaluation of the use of freezer mill to improve DNA retrieval from dried cotton swabs

This investigation evaluated the use of a freezer mill to improve retrieval of DNA from dried cotton swabs (using 100 μl saliva) compared to uncrushed swabs and whole saliva by measuring DNA yield and profile average peak height. Three treatments were tested; short, medium (as for a bone sample) and extended. The samples subjected to the freezer mill had the powder that remained on the freezer mill components collected (using a water and agitation method). All freezer mill samples returned a lower average DNA yield than either uncrushed swabs or whole saliva. The powder from the crushed swabs comprised an average of 35% of the total DNA yield, whereas the powder from the components comprised 65%. Allele drop-out was observed in samples exposed to extended treatments. Both short and medium treatments provided significantly higher peak heights than uncrushed cotton swabs with equal quantities of DNA (P < 0.05). Using a freezer mill on dried cotton swabs does not increase the DNA yield. This investigation suggests collecting powder from the freezer mill components will increase DNA yield, especially from trace samples.     

Comparison of Different Swabs for Sampling Inorganic Gunshot Residue from Gunshot Wounds: Applicability and Reliability for the Determination of Firing Distance

This study concentrates on samples of bare pork skin, with and without bristles, and dried bovine ribs shot with a semi‐automatic pistol to find the best methodology and sampling surface in the search for inorganic gunshot residues (IGSR). Four quadrants of known surface areas were sampled at different distances from the bullet's hole with different swabs: tapes in graphite, Leukosilk® white tape, 3M® transparent tape, and a cotton swab to assess the technique able to collect the highest amounts of IGSR with the lowest contribution of the blank. The cotton swab wet in 10% HNO₃ gave the best results. The highest amounts of IGSR, measured by ICP‐OES and MS, were detected on a surface of 3‐cm radius from the bullet's edge. The amount of metals collected decreased with the firing distance between 20 and 60 cm. The procedure was efficient for sampling different tissues like skin and bones.     

Contribution to the Development of Guidelines in the Analysis of Biological Evidence in Sexual Assault Investigations

This investigation intends to study materials and techniques used for biological evidence collection in sexual assault cases and is divided into two stages: in stage one, methods for biological evidence collection (the single swab (including three variants) and the “double swab technique”) were compared; in stage two, swabs’ component material was compared. The sampling was composed of 42 heterosexual couples who provided mock samples. The collection methods in which the whole swab is covered by evidence presented significantly better outcomes (p < 0.001), such as the “double swab technique.” Additionally, nylon swabs proved to present significantly better features regarding the capacity of sample elution, providing significantly higher amounts of DNA (p ≤ 0.034). This study provides guidelines for better collection of biological evidence regarding the collection method using a swab and the proper swab material to utilize.     

An Optimized DNA Analysis Workflow for the Sampling,Extraction, and Concentration of DNA obtained from Archived Latent Fingerprints

DNA profiles have been obtained from fingerprints, but there is limited knowledge regarding DNA analysis from archived latent fingerprints—touch DNA “sandwiched” between adhesive and paper. Thus, this study sought to comparatively analyze a variety of collection and analytical methods in an effort to seek an optimized workflow for this specific sample type. Untreated and treated archived latent fingerprints were utilized to compare different biological sampling techniques, swab diluents, DNA extraction systems, DNA concentration practices, and post‐amplification purification methods. Archived latent fingerprints disassembled and sampled via direct cutting, followed by DNA extracted using the QIAamp® DNA Investigator Kit, and concentration with Centri‐Sep? columns increased the odds of obtaining an STR profile. Using the recommended DNA workflow, 9 of the 10 samples provided STR profiles, which included 7–100% of the expected STR alleles and two full profiles. Thus, with carefully selected procedures, archived latent fingerprints can be a viable DNA source for criminal investigations including cold/postconviction cases.     

A Comparison of the Effectiveness of Swabbing and Flossing as a Means of Recovering Spermatozoa from the Oral Cavity

This study examined whether flossing the teeth is a more effective collection method in recovering spermatozoa than conventional swabbing techniques. It was hypothesized that inclusion of flossing as a collection method would extend the recovery of spermatozoa to longer postcoital intervals (PCIs). Eighteen individuals provided 174 oral cavity samples. Successful recovery of spermatozoa was assessed with respect to the collection method and reported activity in the oral cavity during the PCI. Samples were subjected to a differential extraction procedure prior to microscopic evaluation of the extracted pellet. The results indicate that swabbing is more effective than flossing when the PCI falls within 1.5–12 h. However, spermatozoa were recovered from seven floss samples where the corresponding swabs gave negative results. When combining the results from the two collection methods, the percentage of subjects from whom spermatozoa are recovered increases for each PCI beyond the 0‐h interval.     

The utility of polyester and cotton as swabbing substrates for the removal of cellular material from surfaces

Various types of cotton and polyester fabrics were tested to ascertain the optimal physical and chemical characteristics of fabrics needed for the removal of cellular material from surfaces. DNA quantitation values obtained on dried saliva stains showed no difference between cotton and polyester across all constructions and solvent conditions. Fabrics used dry and with water yielded higher quantitation values than those used with isopropanol. Quantitation values were also higher for wovens and nonwovens than knits across all solvent conditions. Low thread count fabrics used with water yielded higher quantitation values, but no correlation between thread count and quantitation values was observed with dry fabrics. A low thread count woven fabric, however, outperformed other tested fabrics when swabbing object surfaces in a highly used room. Full DNA profiles from fingerprints on glass surfaces were obtained with low thread count woven and nonwoven fabrics but not with the knit fabric tested.     

Advantage of ForensiX Swabs in Retrieving and Preserving Biological Fluids

This study compares two novel swabs (forensiX) with a standard cotton swab (EUROTUBE) for the collection of saliva stains on glass slide for STR analysis. ForensiX collection tubes are a standard cotton swab in an “active drying” tube, where swab sample is soon dried by its innovative tube surface of the wall. The other is forensiX Nylon Flocked Swab. The study is two phases: The first “phase” assesses swab types regarding to retrieve ability of saliva. The second “phase” compares the drying ability of each swab to assess how crime samples would fare when left in storage. The main result showed that “active drying” is effective to store swabbed sample. The forensiX swabs generally are effective for higher (twofold to fourfold) DNA yield compared to delta lab swab (around 750 pg and 250 pg from 0.5 μL of saliva), respectively. These findings demonstrate the importance of drying performance in the preservation of DNA and swab selection.     

Comparison of the M-Vac® Wet-Vacuum-Based Collection Method to a Wet-Swabbing Method for DNA Recovery on Diluted Bloodstained Substrates*†‡

A wet-vacuum-based collection method with the M-Vac^® was compared to a wet-swabbing collection method by examining the recovery of diluted blood on 22 substrates of varying porosity. The wet-vacuum method yielded more total nuclear DNA than wet-swabbing on 18 porous substrates, recovering on average 12 times more DNA. However, both methods yielded comparable amounts of total DNA on two porous and two nonporous substrates. In no instance did wet-swabbing significantly recover more DNA. The wet-vacuum method also successfully collected additional DNA on previously swabbed substrates. Mitochondrial DNA yields were assessed, and outcomes were generally similar to the nuclear DNA outcomes described above. Results demonstrate that wet-vacuuming may serve as an alternative collection method to swabbing on difficult porous substrates and could potentially recover additional DNA on previously swabbed substrates. However, swabbing remains the preferred collection method on substrates with visible stains and/or nonporous surfaces for reasons of convenience, simplicity, and lower cost relative to the wet-vacuum method.     

Optimization of the collection and analysis of touch DNA traces

The aim of this work was to optimize a strategy for detection, collection, and analysis of touch DNA traces. 4N6FLOWSwabs™ and cotton swabs were compared by collecting touch DNA traces from glass slides and gun shell casings. Shed cells were visualized using Diamond™ nucleic acid dye and a digital fluorescent microscope. Different collection and extraction methods were tested. Collected samples were amplified with the AmpFlSTR® NGMSElect™ kit and the Precision ID mtDNA Whole Genome Panel.     

Evaluation of different sampling media for their potential use as a combined swab for the collection of both organic and inorganic explosive residues

Commercially available skin cleansing alcohol wipes and conventional swabs were investigated for their use as a universal sampling medium for the simultaneous collection of both organic and inorganic explosive residues. Six compounds with the potential to be encountered in casework [pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), triacetone triperoxide (TATP), ammonium nitrate, and sodium chlorate] were selected as representative target compounds. Quantities of these target compounds were deposited on four different substrates (glass, plastic, aluminium foil and laminate). Two chosen alcohol wipes demonstrated better overall performance in the recovery of both the organic and inorganic representative compounds from each of the test surfaces compared to the results obtained using conventional cotton and polyester swabs, pre-moistened with various solvents, and a direct methanol wash (used as a control). Results obtained using dry cotton swabs indicated that it was not an effective swabbing system for the collection of both organic and inorganic explosive residues on common substrates.     

Developmental Validation of the PrepFiler™ Forensic DNA Extraction Kit for Extraction of Genomic DNA from Biological Samples*

Abstract: The PrepFiler? Forensic DNA Extraction Kit enables isolation of genomic DNA from a variety of biological samples. The kit facilitates reversible binding of DNA with magnetic particles resulting in high DNA recovery from samples with very low and high quantities of biological materials: 0.1 and 40 μL of human blood (donor 2) provided 14 and 2883 ng of DNA, respectively. Following the revised SWGDAM guidelines, performance of the developed method was investigated using different sample types including saliva on swabs, semen stains on cotton fabric, samples exposed to environment, samples with polymerase chain reaction (PCR) inhibitors, blood stains (on denim, cotton cloth, and FTA^® paper), and touch evidence‐type samples. DNA yields for all samples tested were equal or better than those obtained by both phenol–chloroform extraction and commercial kits tested. DNA obtained from these samples was free of detectable PCR inhibitors. Short tandem repeat profiles were complete, conclusive, and devoid of PCR artifacts.     

Forensic approach to analyzing rape cases

With large number of criminal acts, such as rape and murder, identification of the perpetrator is very difficult to determine. The cause is the lack of sufficient quantity of biological traces provided as material evidence, or the biological material is decomposed and no result can be obtained by using other identification methods. Thus the case remains unsolved. The purpose of this research is to establish a reliable method for detecting semen presence in rape cases and to get DNA profile from the perpetrator of a crime. Vaginal swabs were taken using cotton swabs during gynecological examination or autopsy in 21 cases. The chemical detection of semen presence was performed using Phospathesmo Kits. The DNA extraction was performed using QIAAamp^® DNA Mini Kit. The amplification was performed using AmpFistrIdentifiler Kit and AmpFistrYfiler Kit. The electrophoresis was performed using 310 ABI squenator. Results indicate that DNA profile was obtained in 4 cases where chemical tests did not prove semen presence using Phospathesmo Kits. In one case, neither semen presence was chemically proven nor DNA profile was obtained for autosomal STRs, but a profile for Y-STRs was obtained. Our analyses indicate that when the victim's body is examined within the first few hours or the first day, a genetic profile of the perpetrator of the criminal act is obtained. Besides using autosomal STRs, we recommend Y-STRs to be used in all rape cases, too, thus separating the male from female profile, and also the male kinship relatedness in cases of incest could be followed, the rape performed by several blood-related men or similar.