Touch Samples Research Articles

Limit Detection of Short Tandem Repeats (STR) Analysis on Touch DNA Samples

Forensic short tandem repeats (STR) profiling on touch DNA samples has emerged as a primary method for human identification. The stability and uniqueness of STR combination from the targeted locus in each individual make it a precision marker for human identification. Touch DNA samples can be found in traces of biological material shed from a person. This work aimed to identify the lowest concentration limit required for generating an interpretable DNA profile and the sensitivity of the STR loci applied. Touch DNA samples were collected from donors who were asked to hold a rope for 5 min. A double swab technique was used to lift the touch samples from the rope. These samples are subjected to DNA extraction and quantification. Two STR amplification cycles, 29 and 34 cycles, were used. DNA concentration greatly influences the success of amplifying the target allele at each STR locus to be interpreted into a complete DNA profile, shown by its allele peak. Touch DNA concentration >0.25 ng can produce a complete DNA profile. LCN method successfully amplified touch DNA with a concentration 0.0625–0.25 ng/µL. Limit detection of touch DNA analysis is 0.25 ng/µL. Low-copy DNA can still be analyzed within 0.0625–0.25 ng/µL.

A Dynamic Selection Method for Touch-Based Continuous Authentication On Mobile Devices

Touch biometric is one of the promising modalities to realise continuous authentication (CA) on mobile devices by distinguishing between touch strokes performed by the legitimate and illegitimate users. While the benefit of the scheme is promising, the effectiveness of different classification methods is not thoroughly understood. Little consideration has been given to dynamic selection of classifiers. In this paper, we proposed a dynamic selection method to deal with the security and usability needs of touch-based CA. Instead of classifying all touch samples using the same classifier, the method classifies each touch sample using the most promising classifier(s) from a pool of classifiers based on a certain measure of competence. The classifiers that achieve the highest level of competence will be selected to perform the classification task. We compared the proposed method with other dynamic selection methods, well-known single classifiers, as well as static ensemble methods. The experimental results show the potential and feasibility of the proposed method to improve the authentication performance of touch-based CA against the benchmark methods. We found that the proposed method can produce promising results with relatively low equal error rate in many scenarios of the datasets, with relatively high consistency.

Tactile Perception in Aesthetic Evaluation: A Systematic Review

Abstract The haptic sense is an essential component of aesthetic evaluation that is often overlooked in today's mobile internet age. Unlike hearing and vision, the sense of touch is less widely transmitted. Unfortunately, most aesthetic theories and explanations have focused solely on the visual and auditory senses, with minimal attention given to tactile evaluation. To address this gap in knowledge, we have collected studies on tactile aesthetics within the framework of experimental aesthetics from 2000 to 2022. After statistical generalization, our findings suggest the following: The criteria for evaluating tactile aesthetics were mostly dichotomous, that is, positive (like/appreciation/pleasure) and negative (dislike/disgust/unpleasant). Tactile aesthetics predominantly involved the toucher dimension (synesthesia/need for touch/touch pattern) and the touch sample dimension (shape/type/texture), with the commonly overlooked factors of “need for touch” and “touch pattern.” Some studies did not restrict the shape and material of the touch samples. Based on our findings, we have systematically summarized and concluded what tactile factors influence aesthetic evaluation and have analyzed future research trends.

Rapid and Sensitive Human-Specific DNA Quantitation Using a Microfluidic Amplification Module at the Point-of-Care.

A rapid microfluidic human-specific DNA quantitation assay module was developed for chip-based amplification of the human TH01 and Alu loci in the presence of PicoGreen. The method makes use of the thermal cycler and 488 nm Solid State laser-based optical train that are components of the fully-integrated, sample-in to results out, ANDE Rapid Nucleic Acid Analysis system. The assay was effective in quantitating human DNA from a variety of sample types, including blood, buccal, and forensic touch samples mixed with varying amounts of non-human DNA. The 28-cycle TH01 and 10-cycle Alu reactions were completed in 18 minutes and 7 minutes, respectively. The observed limit of detection (LOD) of the assay is approximately 0.3 ng, and the flexibility of assay design allows an LOD of as little as 0.005 femtograms.Clinical Relevance-We have developed a fully-integrated, sample-in to results-out, Rapid Nucleic Acid Analysis system that characterizes nucleic acid fragments (whether generated by PCR, rt-PCR, sequencing, or SNP reactions) by electrophoresis in plastic microfluidic channels. Here we describe the development, characterization, and validation of the microfluidic quantitation module. The quantitation module is the first that can be incorporated into integrated microfluidic workflows for the analysis of highly-multiplexed clinical diagnostic assays interrogating hundreds of genomic targets in a single sample. In particular, the use of a microfluidic quantitation module allows reaction volumes, thermal cycling conditions, and electrophoretic injection protocols to be determined based on nucleic acid content during and throughout fully-automated processing-dramatically enhancing the power of the fully-automated diagnostic system.

From clean spaces to crime scenes: Exploring trace DNA recovery from titania-coated self-cleaning substrates

Titanium dioxide (titania, TiO2) is frequently used as a coating for a variety of self-cleaning products, such as antifogging vehicle mirrors, ceramic tiles, and glass windows because of its distinct physiochemical features. When exposed to light TiO2 causes photocatalytic decomposition of organic contaminants, potentially compromising DNA integrity. The impact of TiO2-coated commercial glasses, Bioclean® and SaniTise™, on trace DNA persistence, recovery, and profiling was investigated. DNA in saliva and touch samples deposited on self-cleaning glass slides exposed to indoor fluorescent light for up to seven days was more degraded than control samples indicating some degree of fluorescent light-induced photocatalytic activity of the self-cleaning surfaces. When exposed to sunlight, DNA yields from saliva and touch samples deposited on the titania-coated substrates decreased rapidly, with a corresponding increase in DNA degradation. After three days no DNA samples applied to self-cleaning glass and exposed to natural sunlight yielded STR profiles. These results suggest that the photocatalytic activation of TiO2 is the likely mechanism of action underlying the extreme DNA degradation on the Bioclean® and SaniTise™ glasses. Consequently, rapid sample collection and use may be warranted in casework scenarios involving TiO2-coated materials.

MASS: A Multisource Domain Adaptation Network for Cross-Subject Touch Gesture Recognition

Touch gesture recognition (TGR) plays a pivotal role in many applications, such as socially assistive robots and embodied telecommunication. However, one obstacle to practicality of existing TGR methods is the individual disparities across subjects. Moreover, a deep neural network trained with multiple existing subjects can easily lead to overfitting for a new subject. Hence, how to mitigate the discrepancies between the new and existing subjects and establish a generalized network for TGR is a significant task to realize reliable human–robot tactile interaction. In this article, a novel framework for Multisource domain Adaptation via Shared-Specific feature projection (MASS) is proposed, which incorporates intradomain discriminant, multidomain discriminant, and cross-domain consistency into a deep learning network for cross-subject TGR. Specifically, the MASS method first extracts the shared features in the common feature space of training subjects, with which a domain-general classifier is built. Then, the specific features of each pair of training and testing subjects are mapped and aligned in their common feature space, and multiple domain-specific classifiers are trained with the specific features. Finally, the domain-general classifier and domain-specific classifiers are ensembled to predict the label for the touch samples of a new subject. Experimental results performed on two datasets show that our proposed MASS method achieves remarkable results for cross-subject TGR. The code of MASS is available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://github.com/AI-touch/MASS</uri> .

Quantifying DNA loss in laboratory-created latent prints due to fingerprint processing

Fingerprints, which are associated with touch samples, typically contain a limited amount of DNA. The amount of available DNA can be further reduced when the same touch samples undergo fingerprint processing [1]. The fingerprint development process consists of high-powered lighting (inherent luminescence and UV light) and chemical compounds (ninhydrin, black powder, cyanoacrylate, and rhodamine 6 G) which could reduce DNA quality and quantity. Therefore, forensic scientists often must select one type of analysis over the other due to the destructive nature of processing. DNA and latent fingerprinting are both useful sources for identification, although both can produce partial results. A partial DNA profile may only contain a few alleles, limiting the ability to identify a potential suspect to perform comparisons. A partial fingerprint generally means that only a very small part of the fingerprint is present, which makes comparisons difficult. Because partial results are common, combining data from both fingerprinting and DNA analysis would increase the confidence of an identification of a person. Significant research has been performed to determine if a DNA profile can be obtained from latent processed fingerprints; however, there has yet to be research done in a standardized manner. In this study, we used standardized mock “fingerprints” in order to reduce fingerprint DNA variability and specifically focused on DNA quantitation after each step in the fingerprinting process. Results suggest that latent print processing techniques used on non-porous surfaces (plastic, duct-tape, metal, and rubber) do not affect DNA quantity or quality. In contrast, ninhydrin, a chemical used for processing fingerprints present on porous surfaces (wood and paper), significantly reduced DNA recovery. Together these results suggest that DNA can still be performed on latent print processed items, unless ninhydrin has been used.

Zoom gesture analysis for age-inappropriate internet content filtering

The Internet contains large amounts of adult content. With only a few taps, or mis-taps, an under-aged user can be exposed to age-inappropriate content. Currently, this can be avoided by creating age-restricted profiles or restricting users to child-friendly applications (apps). However, these existing measures are time-consuming, laborious, and require a higher level of technical literacy than many parents can afford. We believe a better solution is to use a browser or an app that automatically detects the user’s age then applies any appropriate content filters. For such a browser/app to be developed, we must learn that age estimation can indeed be performed with an acceptable rate of error. To that end, we created an Android app that collects biometric touchscreen data from elementary school, middle school, high school, and university students. Touch samples were collected from participants aged 5 to 61 on both smartphones and tablets. We focused exclusively on zoom-in and zoom-out touchscreen data samples. We made this decision because we found the zoom gesture to be rich with data and highly used among the most popular applications. Furthermore, we identify a niche within the current research landscape: no other machine learning experiments have leveraged the benefits of the zoom gesture for age estimation. We collected a total of 41,911 zoom data samples. From each zoom sample, 90 features were extracted. Those features were then used to train and test on six regressors and six classifiers to build a method that can accurately estimate the user’s age from their touchscreen behavior. The regressors performed with the best mean absolute errors (MAEs) of 2.27 and 2.54 years for smartphones and tablets, respectively. The classifiers performed with the best accuracies of 90% and 91% for smartphones and tablets, respectively. Given these results, it is our belief that not only is touch-based age estimation viable, but developing a child-safe browser or a parental control app with this underlying technology is a worthwhile endeavor.

Optimization of proteomics sample preparation for forensic analysis of skin samples

We present an efficient protein extraction and in-solution enzymatic digestion protocol optimized for mass spectrometry-based proteomics studies of human skin samples. Human skin cells are a proteinaceous matrix that can enable forensic identification of individuals. We performed a systematic optimization of proteomic sample preparation for a protein-based human forensic identification application. Digestion parameters, including incubation duration, temperature, and the type and concentration of surfactant, were systematically varied to maximize digestion completeness. Through replicate digestions, parameter optimization was performed to maximize repeatability and increase the number of identified peptides and proteins. Final digestion conditions were selected based on the parameters that yielded the greatest percent of peptides with zero missed tryptic cleavages, which benefit the analysis of genetically variable peptides (GVPs). We evaluated the final digestion conditions for identification of GVPs by applying MS-based proteomics on a mixed-donor sample. The results were searched against a human proteome database appended with a database of GVPs constructed from known non-synonymous single nucleotide polymorphisms (SNPs) that occur at known population frequencies. The aim of this study was to demonstrate the potential of our proteomics sample preparation for future implementation of GVP analysis by forensic laboratories to facilitate human identification. SignificanceGenetically variable peptides (GVPs) can provide forensic evidence that is complementary to traditional DNA profiling and be potentially used for human identification. An efficient protein extraction and reproducible digestion method of skin proteins is a key contributor for downstream analysis of GVPs and further development of this technology in forensic application. In this study, we optimized the enzymatic digestion conditions, such as incubation time and temperature, for skin samples. Our study is among the first attempts towards optimization of proteomics sample preparation for protein-based skin identification in forensic applications such as touch samples. Our digestion method employs RapiGest (an acid-labile surfactant), trypsin enzymatic digestion, and an incubation time of 16 h at 37 °C.

How many cells are required for successful DNA profiling?

Through advances in fluorescent nucleic acid dye staining and visualisation, targeted collection of cellular material deposited, for example by touch or within a saliva deposit, is possible. In regard to the potential evidentiary value of the deposit the questions remain: ‘How many cells are required to generate an informative DNA profile?’; ‘How many visualised corneocytes within a touch deposit compared to typical nucleated cells are required in order to achieve successful DNA profiling?’.Diamond TM Nucleic Acid Dye (DD) staining of cellular material, and subsequent visualisation utilising portable fluorescence microscopy, was performed for touch and saliva samples to target defined numbers of cells for collection, by swab and tapelift, and subsequent processing via direct PCR and PCR post-extraction. The resulting DNA quantification data and alleles generated within subsequent DNA profiles could be correlated to the number of cells initially collected to determine cellular threshold requirements for DNA profile generation for each workflow.Full profiles were consistently generated using direct PCR when the template was ≥40 buccal cells collected by either a swab or tapelift. By contrast ≥800 corneocytes collected by swabbing or ≥4,000 corneocytes collected by a tapelift were required to generate same number of STR alleles from touch samples. When samples were processed through a DNA extraction workflow, ≥80 buccal cells were required to generate full profiles from both swab and tapelift, while touch samples required ≥4,000 corneocytes collected by a swab and >8,000 corneocytes collected by a tapelift. The data presented within this study allow for informative sample triage and workflow decisions to be made to optimise STR amplification based on the presence and visual quantification of stained cellular material.

Fractionation of DNA and protein from individual latent fingerprints for forensic analysis

Human touch samples represent a significant portion of forensic DNA casework. Yet, the generally low abundance of genetic material combined with the predominantly extracellular nature of DNA in these samples makes DNA-based forensic analysis exceptionally challenging. Human proteins present in these same touch samples offer an abundant and environmentally-robust alternative. Proteogenomic methods, using protein sequence variants arising from nonsynonymous DNA mutations, have recently been applied to forensic analysis and may represent a viable option looking forward. However, DNA analysis remains the gold standard and any proteomics-based methods would need to consider how DNA could be co-extracted from samples without significant loss. Herein, we describe a simple workflow for the collection, enrichment and fractionation of DNA and protein in latent fingerprint samples. This approach ensures that DNA collected from a latent fingerprint can be analyzed by traditional DNA casework methods, while protein can be proteolytically digested and analyzed via standard liquid chromatography-tandem mass spectrometry-based proteomics methods from the same touch sample. Sample collection from non-porous surfaces (i.e., glass) is performed through the application of an anionic surfactant over the fingermark. The sample is then split into separate DNA and protein fractions following centrifugation to enrich the protein fraction by pelleting skin cells. The results indicate that this workflow permits analysis of DNA within the sample, yet highlights the challenge posed by the trace nature of DNA in touch samples and the potential for DNA to degrade over time. Protein deposited in touch samples does not appear to share this limitation, with robust protein quantities collected across multiple human donors. The quantity and quality of protein remains robust regardless of fingerprint age. The proteomic content of these samples is consistent across individual donors and fingerprint age, supporting the future application of genetically variable peptide (GVP) analysis of touch samples for forensic identification.

Resolving human DNA mixtures with F-108 polymer and capillary electrophoresis single-strand conformational polymorphism analysis.

Current technologies have increased the sensitivity for analyzing forensic DNA samples, especially those considered "touch samples." Because of this, there has been an increase in the number of forensic mixtures-two or more contributors within a single sample-submitted to the crime laboratories. Therefore, the need to resolve these mixtures has increased as well. Several technologies are currently utilized, but many of them are time consuming and do not resolve the entire profile. Therefore, CE-Single-Strand Conformational Polymorphisms coupled with the Pluronic F-108 polymer was assessed for its ability to resolve human forensic mixtures. This technique has been able to detect sequence variation, such as single nucleotide polymorphism in short tandem repeat loci, such as D7S820 and vWA. Samples were first analyzed with the Performance Optimized Polymer-7, and mixtures created from samples that shared alleles. These samples were sequenced to detect single base-pair mutations and evaluated with the F-108 and CE-Single Strand Conformational Polymorphism analysis. Results from this study indicated the method would serve as a valuable screening tool to detect base sequence variation between individuals when they share alleles in a mixture and before using Massive Parallel Sequencing technology to distinguish which bases differ.

Active stylus‐touch discrimination scheme based on anomaly detection algorithm

AbstractThis paper proposes an anomaly detection (AD) algorithm that can discriminate stylus‐touch based on capacitive touch screen panel. The digital value acquired from an analog‐to‐digital converter (ADC) are transferred to an autoencoder including an encoder and a decoder. While the encoder classifies only two classes of a no‐touch and a finger‐touch, the decoder reconstructs the similar sequence to the input one according to the encoder's decision. Because the touch sequences caused by the stylus are not trained, the large difference between input and output sequences is used to discriminate the stylus‐touch from finger‐touch and no‐touch. The proposed method is evaluated by means of an 8‐inch capacitive touch panel, an AD touch detection board, and a stylus board. At the sequence length of 16 touch samples, the measured bit error rate (BER) of less than 10−6 for each touch case is equivalent to the previous support vector machine (SVM) scheme whereas the number of multipliers is dramatically reduced to 16, compared with 400 of the previous SVM method.

Analysis of complex DNA mixtures using massively parallel sequencing of SNPs with low minor allele frequencies

DNA mixtures from 3 or more contributors have proven difficult to analyze using the current state-of-the-art method of short-tandem repeat (STR) amplification followed by capillary electrophoresis (CE). Here we analyze samples from both laboratory-defined mixtures and complex multi-contributor touch samples using a single nucleotide polymorphism (SNP) panel comprised of 2311 low-minor-allele-frequency loci, combined with massively parallel sequencing (MPS). This approach demonstrates that as many as 10 people can be identified in touch samples using a threshold of -Log P(RMNE) of 6, and a detection rate of 18–94 % across 10 different materials using a threshold of -Log P(RMNE) of 2. Thirty-two false positives were observed in 100 touch samples.

Touch DNA in forensic science: The use of laboratory-created eccrine fingerprints to quantify DNA loss

Touch samples typically contain a limited quantity of DNA, which can be further reduced during collection and analysis. It is not clear, however, at which point(s) the majority of the DNA is lost because there is not a reliable positive control to track the quantity of DNA through the analysis procedures. To take the first step in bridging this gap, we established a set of laboratory-created eccrine, or mock, fingerprints containing known quantities of DNA. Next, we defined a set of process controls to quantify loss at key fail points in the collection/extraction procedures, analyzing a total of 1200 mock fingerprints deposited on four different surfaces. We quantified DNA loss to the surface, the swab and at extraction, completing the evaluation with ANOVA. With better understanding of DNA yields and the mechanisms of loss, targeted process improvements will bring touch DNA samples into even more routine use with standardized, optimized procedures.

Prediction of DNA concentration in fingermarks using autofluorescence properties

During criminal investigations trace DNA samples, including fingermarks, are submitted to laboratories for short tandem repeat (STR) analysis. For most common STR analysis systems a minimum amount of input DNA is required. Upon intake by the forensic laboratory the DNA concentration is estimated using quantitative polymerase chain reaction (qPCR) analysis after which most fingermarks are excluded. To tackle the problem of unnecessary processing in the lab, our study aimed to develop a method, which is able to predict the DNA content in fingermarks directly at the crime scene. Upon excitation with a UV Crime-lite, fingermark residues have autofluorescent properties. We hypothesize that the intensity of the autofluorescence signal of the fingermark content correlates to the DNA concentration in fingermarks. In this study, 164 fingermarks were examined on their autofluorescence intensity when excited at 365nm, the number of nucleated cells, their DNA concentration and the completeness of the STR profiles. No significant correlation was observed between the DNA concentration in fingermarks and the autofluorescence signal, indicating that a high amount of autofluorescence, thus a high amount of biomaterial, does not necessarily guarantee a higher amount of DNA. In addition, the completeness of the STR profiles did not correlate to the autofluorescence signal of fingermarks. A moderate correlation was found between the predicted DNA quantity, based on the number of nucleated cells and the DNA quantity. In summary, the autofluorescence signal of fingermarks cannot directly be used as a guide to select fingermarks for DNA analysis directly at the crime scene. However, predicting the amount of DNA using a sensitive and specific DNA staining method can probably be used to estimate the DNA concentration in touch samples.

Direct PCR amplification of DNA from human bloodstains, saliva, and touch samples collected with microFLOQ® swabs

Previous studies have shown that nylon flocked swabs outperform traditional fiber swabs in DNA recovery due to their innovative design and lack of internal absorbent core to entrap cellular materials. The microFLOQ® Direct swab, a miniaturized version of the 4N6 FLOQSwab®, has a small swab head that is treated with a lysing agent which allows for direct amplification and DNA profiling from sample collection to final result in less than two hours. Additionally, the microFLOQ® system subsamples only a minute portion of a stain and preserves the vast majority of the sample for subsequent testing or re-analysis, if desired. The efficacy of direct amplification of DNA from dilute bloodstains, saliva stains, and touch samples was evaluated using microFLOQ® Direct swabs and the GlobalFiler™ Express system. Comparisons were made to traditional methods to assess the robustness of this alternate workflow. Controlled studies with 1:19 and 1:99 dilutions of bloodstains and saliva stains consistently yielded higher STR peak heights than standard methods with 1ng input DNA from the same samples. Touch samples from common items yielded single source and mixed profiles that were consistent with primary users of the objects. With this novel methodology/workflow, no sample loss occurs and therefore more template DNA is available during amplification. This approach may have important implications for analysis of low quantity and/or degraded samples that plague forensic casework.

Improving recovery and stability of touch DNA

Touch samples by their nature do not contain large amounts of biological material, especially compared to biological fluids such as blood, semen or saliva. Consequently, more careful recovery and storage are desirable in order to maximise the amount of DNA available. The main aim of the work presented is to determine whether detergent-based wetting agents increased DNA yield from touch samples when compared to water as a wetting agent. The results show that the use of the detergent-based lysis buffer led to greater DNA recovery from the fingerprints than when distilled water was used. The use of the lysis buffer in the touch DNA sample collection improved DNA recovery and stability over 24h post-collection.

Nanoscale characterization of forensically relevant epithelial cells and surface associated extracellular DNA

Atomic force microscopy provides a novel morphological and physico-chemical perspective to analyze epithelial cell samples in forensic investigations. As a nanoscale, single cell tool, it allows the investigation of scarce samples in a non-destructive fashion. Using chemical force spectroscopy, it permits the identification of specific functional groups or surface molecules. Of specific interest is the presence of extracellular DNA (eDNA) on the surface of epithelial cells that line the exterior skin and interior cavities of human bodies, and can transfer onto surfaces through contact with skin and saliva. To date, this eDNA has only been measured a bulk level. Here, using nanoscale imaging, we first describe the unique differences between keratinized epithelial cells and non-keratinized buccal cells. Then via a force mapping technique, we show how eDNA can be spatially located and quantified on the cell surface. Our results suggest that presence and relative quantity of surface-associated, extracellular DNA signatures can be analyzed on individual epithelial cells from different tissue sources, providing a new tool in the forensic analysis of touch samples.

Analysis of cellular autofluorescence in touch samples by flow cytometry: implications for front end separation of trace mixture evidence

The goal of this study was to survey optical and biochemical variation in cell populations deposited onto a surface through touch or contact and identify specific features that may be used to distinguish and then sort cell populations from separate contributors in a trace biological mixture. Although we were not able to detect meaningful biochemical variation in touch samples deposited by different contributors through preliminary antibody surveys, we did observe distinct differences in red autofluorescence emissions (650–670 nm), with as much as a tenfold difference in mean fluorescence intensities observed between certain pairs of donors. Results indicate that the level of red autofluorescence in touch samples can be influenced by a donor’s contact with specific material prior to handling the substrate from which cells were collected. In particular, we observed increased red autofluorescence in cells deposited subsequent to handling laboratory gloves, plant material, and certain types of marker ink, which could be easily visualized microscopically or using flow cytometry, and persisted after hand washing. To test whether these observed optical differences could potentially be used as the basis for a cell separation workflow, a controlled two-person touch mixture was separated into two fractions via fluorescence-activated cell sorting (FACS) using gating criteria based on intensity of 650–670 nm emissions and then subjected to DNA analysis. Genetic analysis of the sorted fractions provided partial DNA profiles that were consistent with separation of individual contributors from the mixture suggesting that variation in autofluorescence signatures, even if driven by extrinsic factors, may nonetheless be a useful means of isolating contributors to some touch mixtures.Graphical Conceptual workflow diagram. Trace biological mixtures containing cells from multiple individuals are analyzed by flow cytometry. Cells are then physically separated into two populations based on intensity of red autofluorescence using Fluorescence Activated Cell Sorting. Each isolated cell fraction is subjected to DNA analysis resulting in a DNA profile for each contributor.