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

Evaluation of the microbial wet-vacuum system (M-Vac®) for DNA sampling from rough, porous substrates, and its compatibility with fully automated platforms

DNA retrieval methods traditionally used during forensic evidence recovery including swabbing and tape lifting, can have limited effectiveness when used on porous, rough substrates such as bricks and carpet. This is possibly due to the DNA material being dispersed and unreachable for surface sampling techniques. In this evaluation we investigated the effectiveness of the Microbial Wet-Vacuum System (M-Vac®; M-Vac® Systems, Inc., Sandy, UT), as it has been reported to retrieve greater amounts of DNA material from challenging exhibits. A four-stage evaluation was conducted, starting with seeding carpet and brick substrates with a known donor's saliva in two dilutions and comparing the DNA recovery of tape lifting, swabbing, and the M-Vac®. A victim struggle scenario on carpet was then mimicked to compare trace DNA recovery by each method. Two mock scenarios were also conducted; a shirt was submerged in a creek bed for a period of five days to sample for the wearer's DNA, and a car boot was sampled to assess the possibility of recovering a victim's DNA amongst background DNA from the usual car occupants. Finally, the compatibility of the M-Vac® sampling process was optimised for the fully automated DNA lysis and extraction platforms used in the NSW (Australia) jurisdiction by comparing filter subsampling methods. The results from the study were mixed. For bricks, none of the collection methods were effective in retrieving DNA. On carpet, the M-Vac® retrieved the greatest quantities of DNA from the saliva-seeded samples, however, tape lifts outperformed all methods for 'touch' DNA recovery. The M-Vac® retrieved the greatest amount of DNA from the t-shirt recovered from a creek bed as it was able to retrieve the embedded DNA. The final mock case car boot scenario resulted in greater victim DNA recovery from tape lifts, with the M-Vac® more likely to recover mixtures too weak and/or complex to be interpreted. Finally, operational considerations regarding the compatibility of the M-Vac® system with fully automated DNA lysis and extraction are discussed. Considering the substantial time and cost to deploy the M-Vac®, it is recommended to be utilised in casework only after swabbing and tape lifting methods have failed to yield sufficient DNA material, where the substrate properties would likely benefit from the M-Vac's® niche capabilities for retrieving embedded DNA, and low levels of background DNA may be anticipated.

A comparison of six adhesive tapes as tape lifts for efficient trace DNA recovery without the transfer of PCR inhibitors

Tape-lifting is a non-destructive method employed in the laboratory to recover and collect trace DNA evidence from crime scene exhibits with porous surfaces. The success of tape-lifting is a balance between capturing the biological material and compatibility with downstream DNA extraction processes to ensure efficient release of the tape-lifted material during DNA extraction. In this study, six commercially available low-, regular- and high-tack adhesive tapes were evaluated. The low-tack S183 tape and the highly adhesive S-Hold tape were compared for DNA recovery efficiency from different materials commonly encountered in casework. All tape-lifts were processed using PrepFiler Express™ BTA and AutoMate Express™ Forensic DNA extraction systems, DNA samples quantitated by Quantifiler TRIO, amplified using Powerplex® 21 and VeriFiler™ PLUS (VFP), and analysed on a 3500xl genetic analyser to evaluate the quality of the resultant STR profiles obtained. The more adhesive S-Hold tape recovered comparable or more DNA than the low-tack S183 tape from the majority of materials tested. However, STR profiles obtained from S183 tape-lifts were of markedly higher quality compared to S-Hold tape-lifts. This was most evident for towel, denim and printed chiffon, where S-Hold samples exhibited severe PCR inhibition, with VFP internal quality markers confirming the presence of inhibitors. The findings suggest that strong adhesion is not necessarily beneficial for tape-lifting, as the low tack S183 tape was able to efficiently recover cellular material from the surface of porous substrates commonly encountered in casework, while avoiding the co-transfer of PCR-inhibitory substances from the sampled material.

Comparison of swabbing and cutting-out DNA collection methods from cotton, paper, and cardboard surfaces

Choosing an inappropriate method of sample collection can often have a detrimental impact on DNA recovery. Multiple studies highlight the importance of selecting the recovery method based on the type of surface the DNA sample is located on. This study aimed to investigate the efficacy of sample collection via the single cotton swabbing method in comparison to recovery directly from the material cut from the surface. The three types of surfaces included cotton, paper, and cardboard. DNA sources comprised cell-free and cellular DNA, as well as blood and saliva as examples of body fluids commonly encountered at crime scenes. The data analysis revealed that the cutting-out method resulted in higher DNA recovery from all but cardboard surfaces, making it the more efficient collection method. Despite its limitations, the cutting-out method should be considered as the DNA recovery method of choice when suitable.

Effects of solvent-based adhesive removal on the subsequent dual analysis of fingerprint and DNA

The combined approach of classical fingerprinting and DNA profiling is a powerful tool in forensic investigations of latent "touch" traces. However, little attention has been paid to the organic solvents frequently used in dactyloscopic laboratories to facilitate the separation of adhesive evidence prior to fingerprint development and downstream effects on subsequent DNA profiling. In the present study, we tested a selection of adhesive removers (n = 9) and assessed their potential impact on DNA recovery and amplification by PCR. Thereby, we identified and characterized novel PCR inhibitors. All investigated chemicals contain volatile organic compounds that evaporate under normal indoor atmospheric conditions. Exposure to certain solvents resulted in increased DNA degradation, but only if evaporation was prevented. A series of adhesive-removal experiments were conducted with prepared mock evidence (self-adhesive postage stamps affixed to paper envelope) to investigate the impact of treatment time and the location of applied traces on DNA recovery and dactyloscopy, respectively. Due to the early onset of print decomposition, we found that only a short treatment time was compatible with the development of fingerprints on the adhesive side of a stamp. Solvents also removed DNA from the adhesive surface, thus resulting in a marked shift in the substrate distribution of recovered DNA from the stamp to the envelope, but not in the reverse direction. Furthermore, we observed that treatment with conventional fingerprint reagents lead to a significant reduction in the amounts of DNA recovered from stamps, while the additional use of adhesive removers did not significantly enhance this effect.

Effect of swabbing technique and duration on forensic DNA recovery

Various factors have been shown to affect performance of the conventional wet-dry double and single wet swabbing techniques to recover DNA, such as pressure and angle of application, volume and type of wetting agent, and swab type. However, casework laboratories in some jurisdictions have recently adopted different swabbing techniques that include wet-moist double swabbing and moist-dry single swabbing. Factors affecting the effectiveness of these recent techniques in maximising DNA recovery therefore need to be investigated. Here, the performance of traditional and recent swabbing techniques was compared and the impact of swabbing duration on DNA recovery was investigated. Ten µl aliquots of a known concentration of DNA extracted from human blood were deposited on pre-cleaned DNA-free cotton swatches (porous) and porcelain tiles (non-porous). Five swabbing techniques were used, of which three were double swabbing techniques: wet-moist, wet-wet and wet-dry, and two were single swabbing techniques: wet and moist-dry. For a 'wet' or 'moist' swab, 100 or 50 µL water was added, respectively. For a moist-dry swab, water was applied to one side of the swab, leaving the other side drier. Each swabbing technique was applied for two durations, 15 and 30 s per swab, with 5 reps of each combination (n = 100 plus controls). All samples were extracted and quantified, and a sub-set was profiled. The results showed that the wet-moist double swabbing technique with a swabbing duration of 30 s maximised DNA recovery from cotton. From tile, a single wet or moist-dry swab maximised DNA recovery, but increasing swabbing duration from 15 to 30 s had no impact. These data can be used to inform standardisation of DNA collection protocols across casework laboratories.

Recovery techniques for contact DNA traces

Donor DNA profiling can serve at least two purposes: 1) to enhance the evidential value of DNA deposited on garments/ items and 2) to provide valuable tactical information during crime scene investigation. In this review, different types of methods for the recovery of the contact DNA traces have been summarized. Additionally, with the available techniques, the unique characteristics and limitations thereof have been overviewed. The aim of this paper is to review the techniques of touch traces collection. Techniki odzyskiwania śladów kontaktowych DNA Profilowanie DNA dawcy może służyć co najmniej dwóm celom: 1) zwiększeniu wartości dowodowej DNA zdeponowanego na odzieży/przedmiotach oraz 2) dostarczeniu cennych informacji taktycznych podczas badania miejsca przestępstwa. W niniejszym przeglądzie podsumowano różne rodzaje metod odzyskiwania śladów kontaktowych DNA. Dodatkowo, w odniesieniu do dostępnych technik, dokonano przeglądu ich unikalnych cech i ograniczeń. Celem niniejszej pracy jest przegląd technik pozyskiwania śladów dotykowych.

An evaluation of two adhesive media for the recovery of DNA from latent fingermarks: A preliminary study

Dual recovery of forensic evidence is beneficial for crime scene and evidence processing as it can potentially double the evidential value of a single source, even more so in instances of DNA fingermarks. The use of adhesive liftering media has shown comparable results to swabbing when dealing with trace DNA recovery. Gelatine lifters have displayed the potential to recover DNA from latent fingermarks with minimal alteration to friction ridge detail post application, yet their ability to recover DNA has not fully been explored. The aim of this research was to compare the use of gelatine lifters with more readily available masking tape in their ability to recover cellular material from latent fingermarks. Natural (n = 120) and sebaceous (n = 120) fingermarks were deposited and aged in time frames from fresh, 1-day, 2-day, 1-week, 2-weeks, and 1 month. DiamondTM Nucleic Acid Dye was used as a visualisation method for any DNA containing cellular material. Images of the fingermarks pre and post lifting, and on the lifting media were imaged using the DSC®5 system. The media's ability to recover cellular material was assessed using fluorescent particle analysis by the employment of the free software ImageJ. Fluorescent particles could be observed on the lifting media post lifting with the use of DiamondTM Dye. Time was not seen to influence the variation in the number of fluorescent particles observed. The use of gelatine lifters was found to have a higher amount of recovered DNA containing cellular material than masking tape. Visualisation of particles on masking tape were inhibited by its porosity and absorption of the dye. Some fingermark detail could be observed in the gelatine lifters. The DSC®5 system was suitable for imaging fingermarks stained with DiamondTM Dye.

The DNA-Buster: The evaluation of an alternative DNA recovery approach

Touch DNA recovery techniques can have limitations, as their effectiveness depends on the substrate on which the DNA of a person of interest can be found. In this study, an in-house dry-vacuuming device, the DNA-Buster, was compared to traditional methods for its DNA recovery performance from items typically examined in forensic casework. The aim was to evaluate whether this dry-vacuuming approach can recover DNA efficiently, potentially complementing the well-established recovery strategies. For this, the performances of swabbing, taping, wet- (M-Vac®) and dry-vacuuming (DNA-Buster) were investigated quantitatively and qualitatively for touch DNA deposited on carpet, cotton sweater, stone, tile and wood. For the sweater, both vacuuming methods outperformed the other collection tools quantitatively. While the highest DNA amounts for the carpet were yielded by swabbing and taping, dry-vacuuming was equally good in reaching full DNA profiles, whereas less complete profiles were observed for the M-Vac®. For stone and tile, swabbing was optimal, whereas dry-vacuuming clearly underperformed for these substrates. Taping was the best recovery method for wood. Despite applying single donor DNA after thoroughly cleaning the items, undesired DNA mixtures were detected for all recovery techniques and all substrates. The overall research findings show first that the novel dry-vacuuming method is suited for DNA recovery from textiles. Secondly, they indicate that more attention should be paid to the substrate-collection dependency to ensure best practices in recovering genetic material in a precise, confident and targeted manner from the variety of forensic casework material.

Touch DNA Sampling Methods: Efficacy Evaluation and Systematic Review

Collection and interpretation of "touch DNA" from crime scenes represent crucial steps during criminal investigations, with clear consequences in courtrooms. Although the main aspects of this type of evidence have been extensively studied, some controversial issues remain. For instance, there is no conclusive evidence indicating which sampling method results in the highest rate of biological material recovery. Thus, this study aimed to describe the actual considerations on touch DNA and to compare three different sampling procedures, which were "single-swab", "double-swab", and "other methods" (i.e., cutting out, adhesive tape, FTA® paper scraping), based on the experimental results published in the recent literature. The data analysis performed shows the higher efficiency of the single-swab method in DNA recovery in a wide variety of experimental settings. On the contrary, the double-swab technique and other methods do not seem to improve recovery rates. Despite the apparent discrepancy with previous research, these results underline certain limitations inherent to the sampling procedures investigated. The application of this information to forensic investigations and laboratories could improve operative standard procedures and enhance this almost fundamental investigative tool's probative value.

An Advanced Tape-Stripping Approach for High-Efficiency Sampling on Non-Absorbent Surfaces

Surface sampling is a frequent task in laboratory work and field studies. Simple methods usually have low efficiency in collecting target substances from surfaces. This study developed an advanced tape-stripping approach for efficient sampling on non-absorbent surfaces. A film-forming solution, prepared using polyvinyl alcohol, is applied to the target surface, where it covers and engulfs the surface deposits and then solidifies into an elastic membrane as it is exposed to air. The deposits are collected by stripping off the membrane and re-dissolving it in water. This new approach exhibited an efficiency of 100% in collecting uniform-size microspheres from glass surfaces and extremely high efficiencies (>96.6%) in detecting selected target DNA materials from glass and stainless steel surfaces. In comparison, the common swab-rinse method exhibited an efficiency of 72.6% under similar measuring conditions. The viability of S. aureus during sampling using the new approach decreased as the ethanol concentration in the applied solution increased. Using a solution with a mass ratio of ethanol of 17.6% balanced the effects of multiplication and degradation of the S. aureus on glass surfaces during sampling. Overall, the proposed approach exhibits high efficiency in collecting living and abiotic matter from non-absorbent surfaces, complementing existing sampling methods.

Sampling touch DNA from human skin following skin-to-skin contact in mock assault scenarios-A comparison of nine collection methods

Collection of touch DNA from an offender on the victim's skin can provide relevant evidence for investigations of criminal cases. Therefore, the choice of the optimal sample collection method is crucial. In this study, we investigated the recovery of STR profiles from touch DNA on human skin by comparing nine different collection methods: the dry and wet cotton swabs in three different movements, the double-swab (wet-dry) method, the wet and dry Copan FLOQSwabs™, and the Scene Safe FAST™ minitapes. Mock assault scenarios were conducted with a male offender grasping the forearms of a female victim. Samples were collected from the assaulted area of the victim's skin, and the recovery of the offender's STR profile was evaluated. Our results indicate that the different swabs and swabbing techniques did not have a distinct impact on the STR recovery; however, the lowest STR recovery was achieved with Scene Safe FAST™ minitapes. In addition, we compared the double-swab method to the single-swab method by analyzing the DNA quantity of the wet and dry swabs separately. We found on average 13.7% more offender DNA using the double-swab method, but this did not translate into higher STR recovery. Our findings indicate that several methods perform equally well when collecting touch DNA from human skin, although SceneSafe FAST™ minitapes seem to be the least adequate for this purpose.

Micromanipulation of single cells and fingerprints for forensic identification

Crime scene samples often include biological stains, handled items, or worn clothes and may contain cells from various donors. Applying routine sample collection methods by using a portion of a biological stain or swabbing the entire suspected touched area of the evidence followed by DNA extraction often leads to DNA mixtures. Some mixtures can be addressed with sophisticated interpretation protocols and probabilistic genotyping software resulting in DNA profiles of their contributors. However, many samples remain unresolved, providing no investigative information. Samples with many contributors are often the most challenging samples in forensic biology. Examples include gang rape situations or where the perpetrator's DNA is present in traces among the overwhelming amounts of the victim's DNA. If this is the only available evidence in a case, it is of paramount importance to generate usable information. An alternative approach, to address biological mixtures, could be the collection of individual cells directly from the evidence and testing them separately. This method could prevent cells from being inadvertently blended during the extraction process, thus resulting in DNA mixtures. In this study, multiple tools coupled with adhesive microcarriers to collect single cells were evaluated. These were tested on epithelial (buccal) and sperm cells, as well as on touched items. Single cells were successfully collected but fingerprints were swabbed in their entirety to account for the extracellular DNA of these samples and the poor DNA quality of shed skin flakes. Furthermore, micromanipulation devices, such as the P.A.L.M.® and the Axio Zoom.V16 operated manually or with a robotic arm aureka®, were compared for their effectiveness in collecting cells. The P.A.L.M.® was suitable for single cell isolation when smeared on membrane slides. Manual or robotic manipulations, by utilizing the Axio Zoom.V16, have wider applications as they can be used to isolate cells from various substrates such as glass or membrane slides, tapes, or directly from the evidence. Manipulations using the Axio Zoom.V16, either with the robotic arm aureka® or manually, generated similar outcomes which were significantly better than the outcomes by using the P.A.L.M.®. Robotic manipulations using the aureka® produced more consistent results, but operating the aureka® required training and often needed re-calibrations. This made the process of cell manipulations slower than when manually operated. Our preferred method was the manual manipulations as it was fast, cost effective, required little training, but relied on a steady hand of the technician.

DNA recovery from unfired and fired cartridge cases: A comparison of swabbing, tape lifting, vacuum filtration, and direct PCR

The ability to recover trace DNA from fired cartridge cases can help establish important leads regarding the handler of the ammunition. Over recent years, several DNA recovery techniques for fired ammunition have been published. Three techniques of significant interest include tape lifting, direct PCR, and vacuum filtration. This study aimed to compare these to the swabbing method currently employed in our jurisdiction. Brass and nickel cartridges of five different calibres were spiked with 20ng of saliva and subject to DNA collection using all four DNA recovery methods. Unfired and fired cartridges were tested to examine the effects of firing. Swabbing recovered a greater quantity of DNA than vacuum filtration while no significant differences were found between swabbing and tape-lifting. The calibre of ammunition had no effect on DNA recovery. Firing significantly reduced DNA yield from nickel cartridges, while unfired brass cartridges returned less DNA than unfired nickel cartridges. PCR inhibition was not observed in any samples, although degradation indices suggested that most samples were slightly or moderately degraded. Analysis of profiles showed that swabbing and tape lifting resulted in greater numbers of alleles from fired nickel and brass cartridges compared to direct PCR. Samples from nickel cartridges were found to have a greater number of uploadable profiles than samples from brass cartridges. In addition, three mixed profiles were obtained from the single source spiked cartridges as well as evidence of pre-existing DNA on uncleaned cartridges and contaminating alleles on cleaned cartridges. Our results suggest that tape-lifting can be a suitable alternative to swabbing, but that caution must be taken when interpreting profiles from fired cartridge cases as small amounts of DNA not associated with the handling of the cartridges may be present.

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.

Touch DNA: impact of handling time on touch deposit and evaluation of different recovery techniques: An experimental study

"Touch DNA" is DNA obtained from biological material transferred from a donor to an object or a person during physical contact. This particular kind of evidence could play an essential role in forensic laboratory work and is considered an important tool for investigators. Even though the principal aspects of "Touch DNA" have been extensively studied, to date, there are few reports in the research field of DNA retrieval from garments that have been worn. This study aimed to investigate the "handling time", analyzing particularly the minimum contact time required to deposit a sufficient amount of DNA on a garment to produce an interpretable profile of the "handler". Moreover, three different sampling techniques were compared ("dry swab", "cutting out", and "adhesive tape") with the aim of defining the technique that guarantees the best recovery of the three methods tested. Analyzing the data of this experimental model, a "handling time" of two seconds is enough to release sufficient DNA on to a garment to obtain a complete profile. Moreover, this study demonstrated that when targeting for foreign DNA, the sample area should be narrowed down as much as possible to the smallest area possible to maximize target DNA recovery.

DNA recovery from gelatin fingerprint lifters by direct proteolytic digestion

Fingerprints are a valuable source for DNA profiling in forensic investigations. In practice, the fingerprints are routinely visualized first by powder staining and then often transferred to tapes or gelatin lifters for storage or examination. If at all, fingerprints are usually sampled for DNA in a second step. To target the DNA sampling in an optimal way, it is essential to know how much of the DNA in the sample remains in place and how much is transferred to the lifter. In the present study we addressed this question analyzing 16 pairs of thumb prints and revealed that more than 80% of the DNA from a fingerprint is transferred to the gelatin lifter. Therefore, subsequent DNA sampling of the stored gelatin lifters appears more promising than recovery of the residual DNA from the original fingerprint. Furthermore, as a proof of principle, we developed a protocol for the direct extraction of DNA from gelatin fingerprint lifters by proteolytic digestion of the gelatin matrix followed by organic extraction. We show that DNA recovery from gelatin lifters by this direct extraction protocol is more efficient compared to swabbing the lifter followed by standard magnetic bead extraction of swabs. However, given the more elaborate protocol for direct extraction, we would still recommend the swab technique as the method of choice for forensic routine work.

DNA testing in homicide investigations

Objectives With the widespread use of DNA testing, police, death investigators, and attorneys need to be aware of the capabilities of this technology. This review provides an overview of scenarios where DNA evidence has played a major role in homicide investigations in order to highlight important educational issues for police, death investigators, forensic pathologists, and attorneys. Methods This was a nonrandom, observational, retrospective study. Data were obtained from the collective files of the authors from casework during a 15-year period, from 2000 through 2014. Results A series of nine scenarios, encompassing 11 deaths, is presented from the standpoint of the police and death investigation, the forensic pathology autopsy performance, the subsequent DNA testing of evidence, and, ultimately, the final adjudication of cases. Details of each case are presented, along with a discussion that focuses on important aspects of sample collection for potential DNA testing, especially at the crime scene and the autopsy. The presentation highlights the diversity of case and evidence types in which DNA testing played a valuable role in the successful prosecution of the case. Conclusions By highlighting homicides where DNA testing contributed to the successful adjudication of cases, police, death investigators, forensic pathologists, and attorneys will be better informed regarding the types of evidence and situations where such testing is of potential value.

Laundry in a washing machine as a mediator of secondary and tertiary DNA transfer

The aim of this work was to investigate the possibility of secondary and tertiary DNA transfer during laundry. The modes of transfer tested were mixed and separate laundry of worn and unworn garments in household and public washing machines. In addition, the possibility of a background DNA carry-over from a washing machine's drum was investigated. In the mixed (worn and unworn garments washed together) laundry experiment, 22% of samples from new unworn socks with no traceable DNA prior to experiment produced DNA profiles post-laundry. In the tertiary DNA transfer experiment performed in a public washing machine (unworn garments only), no detectable DNA profiles were observed. Samples collected from the internal drum of 25 washing and drying machines did not produce detectable STR profiles. The implications of these results are discussed in the context of forensic DNA casework analysis. Graphical Abstract ᅟA real-life scenario of secondary DNA transfer between worn and unworn garments during machine washing has been evaluated. Experiments demonstrated this scenario is possible (22% of samples) and may in fact result in high quality DNA profiles. On the contrary, testing washing machine's interior for deposition of biological material between separate washing cycles to serve as a mediator of tertiary DNA transfer resulted in no DNA profiles.

Comparison of preprocessing methods and storage times for touch DNA samples

Aim

To select appropriate preprocessing methods for different substrates by comparing the effects of four different preprocessing methods on touch DNA samples and to determine the effect of various storage times on the results of touch DNA sample analysis.

Method

Hand touch DNA samples were used to investigate the detection and inspection results of DNA on different substrates. Four preprocessing methods, including the direct cutting method, stubbing procedure, double swab technique, and vacuum cleaner method, were used in this study. DNA was extracted from mock samples with four different preprocessing methods. The best preprocess protocol determined from the study was further used to compare performance after various storage times. DNA extracted from all samples was quantified and amplified using standard procedures.

Results

The amounts of DNA and the number of alleles detected on the porous substrates were greater than those on the non-porous substrates. The performances of the four preprocessing methods varied with different substrates. The direct cutting method displayed advantages for porous substrates, and the vacuum cleaner method was advantageous for non-porous substrates. No significant degradation trend was observed as the storage times increased.

Conclusion

Different substrates require the use of different preprocessing method in order to obtain the highest DNA amount and allele number from touch DNA samples. This study provides a theoretical basis for explorations of touch DNA samples and may be used as a reference when dealing with touch DNA samples in case work.

Noninvasive sample collection for the genotyping of neonatal rats using adhesive tape

To develop a noninvasive sample collection method for genotyping, we compared PCR products from samples collected from neonates using five different brands of adhesive tape. Next, the youngest application age to distinguish genotypes was established. The tapes were applied on the backs of rats on postnatal day (PND) 10. DNA extracts from two brands provided clear PCR products that enabled genotype identification. The youngest age for distinguishing genotypes was PND 5; however, the youngest age that provided accurate results was PND 7. Thus, the present method allows for genotyping during the neonatal period without invasive burden and may improve animal welfare by refining.

Combined recovery of biological and fibre traces

We present a method in which DNA and fibre traces are jointly recovered by taping. The DNA traces are isolated by standard laboratory procedures. Fibre traces are isolated afterwards in order to improve efficiency. Two tests have been carried out to evaluate the suitability of the presented method. In the first test, possible changes in appearance of fibres due to the DNA isolation procedures are investigated. In the second test, the recovery of fibres from a contaminated surface and their possible loss due to the DNA isolation procedure are investigated. It is concluded that polyester fibres are hardly affected by the DNA isolation procedure. In contrast, a relatively large number of the investigated cotton fibres were altered. The observed differences do not indicate a structural damage to the fibre or the dyes, but rather the washing-out of some components. The observed changes may require that fibres from a known source are also exposed to the DNA isolation procedures to assess the induced changes, but do not prevent a meaningful comparison. The recovery of fibres is slightly lower than the routine procedures for fibre recovery. Therefore, it was decided to perform extra taping of the recipient in cases where fibre investigation is requested. During DNA-isolation, some of the fibres present are released from the tapes. These fibres are not lost however, as they can be found on the filter in the used DNA isolation vials.

RNA/DNA co-analysis on aged bloodstains from adhesive tapes used for gunshot residue collection from hands

In cases of firearm related fatalities a systematic investigation at the scene of death is indispensable to differentiate between self-inflicted and homicidal gunshot injuries. A common method to preserve gunshot residues (GSR) is their collection using adhesive tapes. However, the biological material gathered at the same time by the tapes would be of special interest if backspatter, ejected from the entrance wound against the direction of fire, could be detected. In the present study we examined the success rate of co-analysis of RNA and DNA recovered from biological traces sampled with adhesive tapes. The material originated from eight cases of fatal gunshots, taken from the hands of suspects or victims, examined 5 to 19 years ago for GSR. For all types of adhesive tapes tested, quantity and quality of the co-extracted nucleic acids was insufficient for successful DNA profiling, but was sufficient for the detection of blood-specific micro RNA (miRNA). In summary, sampling trace evidence from the hands of persons involved in fatal gunshots with adhesive tapes has a long-term detrimental effect on biological traces.

Clinical application of a molecular assay for the detection of dermatophytosis and a novel non-invasive sampling technique

The dermatophytoses are the most common superficial fungal infections worldwide. Clinical diagnosis is not reliable as there are many differentials, and laboratory diagnosis is required to gain access to treatment in more severe disease. Traditional diagnostic methods are limited by suboptimal sensitivity, specificity and prolonged turnaround times. Molecular methods are being used increasingly in the diagnostic algorithm in the clinical microbiology laboratory. The aim of this study was to evaluate a real-time polymerase chain reaction (RT-PCR) targeting the chitin synthase 1 gene (CHS1) of dermatophytes for analytical specificity, and to assess its clinical application by comparing it to the current methods of microscopy and culture. We also assessed a novel non-invasive sample collection technique involving adhesive tape impressions of suspected lesions. The PCR was highly specific, being able to discern between cultures of dermatophytes and other microorganisms. It also proved to be more sensitive than traditional methods at detecting dermatophytes in clinical samples. Similar sensitivities were seen on the samples assessed by the adhesive tape technique. An internal control system allowed for the detection of inhibition in certain culture and clinical specimens. This rapid and cost-effective technique could be incorporated into the initial diagnostic algorithm for dermatophytosis in Australian laboratories.

A novel cell culture model as a tool for forensic biology experiments and validations

To improve and advance DNA forensic casework investigation outcomes, extensive field and laboratory experiments are carried out in a broad range of relevant branches, such as touch and trace DNA, secondary DNA transfer and contamination confinement. Moreover, the development of new forensic tools, for example new sampling appliances, by commercial companies requires ongoing validation and assessment by forensic scientists. A frequent challenge in these kinds of experiments and validations is the lack of a stable, reproducible and flexible biological reference material. As a possible solution, we present here a cell culture model based on skin-derived human dermal fibroblasts. Cultured cells were harvested, quantified and dried on glass slides. These slides were used in adhesive tape-lifting experiments and tests of DNA crossover confinement by UV irradiation. The use of this model enabled a simple and concise comparison between four adhesive tapes, as well as a straightforward demonstration of the effect of UV irradiation intensities on DNA quantity and degradation. In conclusion, we believe this model has great potential to serve as an efficient research tool in forensic biology.

Preliminary investigation of differential tapelifting for sampling forensically relevant layered deposits

The analysis of DNA mixtures can be problematic, especially when in trace quantities such as when a biological sample is deposited onto a substrate which contains background DNA (for example, in the case of touch DNA deposited onto a garment containing the wearer's DNA). We conducted a preliminary investigation into the possibility of removing such multi-donor deposits layer by layer using a differential tape-lifting method. Two types of tape were tested using two different numbers of applications for sampling layered deposits of touch DNA/touch DNA and touch DNA/saliva, both on the same polyester-cotton plain woven material. The data showed that there was no significant increase in the ratio of secondary to primary deposit when sampled in this manner, compared to direct extraction from cuttings of the touched fabric. A similar result was also obtained even when the deposits were on opposing surfaces of the fabric and the sampling was carried out on the secondary deposit side. These findings indicate that biological material, whether touch DNA or saliva, does not predominantly remain on the side of the fabric on which it is deposited (at least for plain-woven polyester-cotton). They also highlight the importance of considering substrate properties when making assumptions as to the resulting location of biological materials from a deposition event, and the necessity to conduct further research on the interactions between substrates and deposits.

Pre-PCR processing in bioterrorism preparedness: improved diagnostic capabilities for laboratory response networks

Diagnostic DNA analysis using polymerase chain reaction (PCR) has become a valuable tool for rapid detection of biothreat agents. However, analysis is often challenging because of the limited size, quality, and purity of the biological target. Pre-PCR processing is an integrated concept in which the issues of analytical limit of detection and simplicity for automation are addressed in all steps leading up to PCR amplification--that is, sampling, sample treatment, and the chemical composition of PCR. The sampling method should maximize target uptake and minimize uptake of extraneous substances that could impair the analysis--so-called PCR inhibitors. In sample treatment, there is a trade-off between yield and purity, as extensive purification leads to DNA loss. A cornerstone of pre-PCR processing is to apply DNA polymerase-buffer systems that are tolerant to specific sample impurities, thereby lowering the need for expensive purification steps and maximizing DNA recovery. Improved awareness among Laboratory Response Networks (LRNs) regarding pre-PCR processing is important, as ineffective sample processing leads to increased cost and possibly false-negative or ambiguous results, hindering the decision-making process in a bioterrorism crisis. This article covers the nature and mechanisms of PCR-inhibitory substances relevant for agroterrorism and bioterrorism preparedness, methods for quality control of PCR reactions, and applications of pre-PCR processing to optimize and simplify the analysis of various biothreat agents. Knowledge about pre-PCR processing will improve diagnostic capabilities of LRNs involved in the response to bioterrorism incidents.

The importance of scientific evaluation of biological evidence--data from eight years of case review

In 2009, the National Research Council published a report stating that the addition of more science and technology into the field of forensic science in the United States would be of great benefit to the judicial system. As a starting point to address this NRC report, one needs to make an assessment of the system. One factor that is continuously requested is an estimate of an error rate. In any given scientific area of forensics that is difficult to quantitate except by external review and audits. After eight years of requested defense review of cases with biological and DNA evidence, most cases appear to be scientifically sound in test methods and procedures. However, there were some cases where errors in the forensic science process did occur. This article takes information compiled from those eight years of defense review and summarizes the cases where errors have been discovered and discusses the scientific implications of these errors. The scope of this article is limited to crime scene collection and forensic science laboratory testing of biological materials for body fluid identification and DNA individualization to a source. The greatest value of defense review comes from (a) providing effective balance and independent oversight to the judicial process and (b) collecting data into a format that can be useful as a guide in training programs.