The Experts below are selected from a list of 8901 Experts worldwide ranked by ideXlab platform
James P Landers - One of the best experts on this subject based on the ideXlab platform.
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acoustic differential extraction for Forensic Analysis of sexual assault evidence
Analytical Chemistry, 2009Co-Authors: Jessica V Norris, Mikael Evander, Katie M Horsmanhall, Johan Nilsson, Thomas Laurell, James P LandersAbstract:Forensic DNA Analysis of samples obtained from sexual assault evidence relies on separation of male and female components of the recovered genetic material. The conventional separation method used by crime laboratories, differential extraction (DE), is one of the most time-consuming sample preparation steps, requires extensive sample handling, is difficult to automate, and often results in inefficient separation of female DNA from the male sample components. To circumvent conventional DE, acoustic differential extraction (ADE) Analysis was developed on a microfluidic device. The ADE method relies on acoustic trapping of sperm cells in the presence of epithelial cell lysate (which is unretained), and laminar flow valving to direct the male and female fractions to separate outlets. Following the separation of sperm from epithelial cell lysate, DNA extraction, quantitation, amplification, and separation were performed using conventional laboratory methods. The results show that highly purified male and female fractions can be obtained with the ADE microdevice from mock sexual assault samples in 14 min. ADE Analysis provides the potential to significantly alter the means by which sexual assault evidence is processed in crime laboratories.
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acoustic differential extraction for Forensic Analysis of sexual assault evidence
Analytical Chemistry, 2009Co-Authors: Jessica V Norris, Mikael Evander, Katie M Horsmanhall, Johan Nilsson, Thomas Laurell, James P LandersAbstract:Forensic DNA Analysis of samples obtained from sexual assault evidence relies on separation of male and female components of the recovered genetic material. The conventional separation method used by crime laboratories, differential extraction (DE), is one of the most time-consuming sample preparation steps, requires extensive sample handling, is difficult to automate, and often results in inefficient separation of female DNA from the male sample components. To circumvent conventional DE, acoustic differential extraction (ADE) Analysis was developed on a microfluidic device. The ADE method relies on acoustic trapping of sperm cells in the presence of epithelial cell lysate (which is unretained), and laminar flow valving to direct the male and female fractions to separate outlets. Following the separation of sperm from epithelial cell lysate, DNA extraction, quantitation, amplification, and separation were performed using conventional laboratory methods. The results show that highly purified male and femal...
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Forensic DNA Analysis on microfluidic devices a review
Journal of Forensic Sciences, 2007Co-Authors: Katie M Horsman, Joan M Bienvenue, R Kiev B S Blasier, James P LandersAbstract:The advent of microfluidic technology for genetic Analysis has begun to impact Forensic science. Recent advances in microfluidic separation of short-tandem-repeat (STR) fragments has provided unprecedented potential for improving speed and efficiency of DNA typing. In addi- tion, the analytical processes associated with sample preparation--which include cell sorting, DNA extraction, DNA quantitation, and DNA amplifica- tion--can all be integrated with the STR separation in a seamless manner. The current state of these microfluidic methods as well as their advantages and potential shortcomings are detailed. Recent advances in microfluidic device technology, as they pertain to Forensic DNA typing, are discussed with a focus on the Forensic community.
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separation of sperm and epithelial cells in a microfabricated device potential application to Forensic Analysis of sexual assault evidence
Analytical Chemistry, 2005Co-Authors: Katie M Horsman, Susan L R Barker, Jerome P Ferrance, Kymberly A Forrest, Katherine A Koen, James P LandersAbstract:Forensic DNA Analysis of sexual assault evidence requires separation of DNA from epithelial (victim) and sperm (perpetrator) cells. The conventional method used by crime laboratories, which is termed “differential extraction”, is a time-consuming process. To supplant the conventional process, separation of sperm from a biological mixture containing epithelial cells has been demonstrated on a microfluidic device. This separation utilizes the differential physical properties of the cells that result in settling of the epithelial cells to the bottom of the inlet reservoir and subsequent adherence to the glass substrate. As a result, low flow rates can be used to separate the sperm cells from the epithelial cell-containing biological mixture. Following cell separation on the microdevice, DNA extraction, amplification, and separation were performed using conventional laboratory methods, showing that the cell separation product in the outlet reservoir was of male origin. The reported cell separation has the pot...
Peter Gill - One of the best experts on this subject based on the ideXlab platform.
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Characterization of degradation and heterozygote balance by simulation of the Forensic DNA Analysis process
International Journal of Legal Medicine, 2017Co-Authors: Oskar Hansson, Thore Egeland, Peter GillAbstract:Simulation experiments were used to show the impact of varying extraction efficiency, aliquot proportion, and PCR efficiency on the heterozygote balance of a range of diploid and haploid cells. Reducing either parameters introduces variance. It is well-known that the variance in heterozygote balance increases as the amount of DNA is reduced. Surprisingly the distribution is in fact diamond shaped — the variance start to decrease at very low amounts of DNA. Simulations suggest that pristine diluted DNA is an acceptable approximation in validations to infer heterozygote balance. However, the difference in distribution of the variance between diploid and haploid cell types may, under some circumstances, need to be considered in statistical models. Finally, we exemplify how simulations can be used to predict the outcome of PCR for degraded samples. Visualizing the predicted DNA profile as an electropherogram can help to identify the best approach for sample processing.
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secondary and subsequent DNA transfer during criminal investigation
Forensic Science International-genetics, 2015Co-Authors: Peter Gill, Thore Egeland, Ane Elida FonnelopAbstract:Abstract With the introduction of new multiplex PCR kits and instrumentation such as the Applied Biosystems 3500xl, there has recently been a rapid change in technology that has greatly increased sensitivity of detection so that a DNA profile can routinely be obtained from only a few cells. Research to evaluate the risks of passive transfer has not kept pace with this development; hence the risk of innocent DNA transfer at the crime-scene is currently not properly understood. The purpose of this study was to investigate the possibility of investigator-mediated transfer of DNA traces with disposable nitrile-gloves used during crime-scene examinations. We investigated the primary transfer of freshly deposited DNA from touched plastic, wood or metal substrates and secondary and tertiary transfer by a person wearing disposable nitrile-gloves and onto a third object. We show that with use of the new highly sensitive technologies available in Forensic DNA Analysis there is an enhanced probability to obtain a DNA-profile which has not been directly deposited on the object but is an outcome of one or more transfer events. The nitrile-gloves used by investigators during exhibit examination can act as a vector for DNA transfer from one item to another. We have shown that the amount of DNA deposited on an object affects the probability of transfer. Secondly, the type of substrate material that DNA is deposited onto has an impact on transfer rates.
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a comparison of stochastic variation in mixed and unmixed casework and synthetic samples
Forensic Science International-genetics, 2012Co-Authors: Joanne Bright, Kurt Mcmanus, Peter Gill, Sally Ann Harbison, John BuckletonAbstract:Understanding the behaviour of mixed DNA profiles is of paramount importance in Forensic DNA Analysis. Key parameters are those of heterozygote balance and mixture proportion and its variability. These parameters have been previously explored as a function of the average peak height of the active alleles in single source and mixed samples derived from pristine DNA. Here we report a comparison of this data with data obtained from casework samples. This allows an assessment of the difference in the distribution of heterozygote balance between mixed and single source stains and between casework mixtures and synthetic mixtures constructed from pristine DNA.
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encoded evidence DNA in Forensic Analysis
Nature Reviews Genetics, 2004Co-Authors: Mark A Jobling, Peter GillAbstract:Sherlock Holmes said "it has long been an axiom of mine that the little things are infinitely the most important", but never imagined that such a little thing, the DNA molecule, could become perhaps the most powerful single tool in the multifaceted fight against crime. Twenty years after the development of DNA fingerprinting, Forensic DNA Analysis is key to the conviction or exoneration of suspects and the identification of victims of crimes, accidents and disasters, driving the development of innovative methods in molecular genetics, statistics and the use of massive intelligence databases.
Jessica V Norris - One of the best experts on this subject based on the ideXlab platform.
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acoustic differential extraction for Forensic Analysis of sexual assault evidence
Analytical Chemistry, 2009Co-Authors: Jessica V Norris, Mikael Evander, Katie M Horsmanhall, Johan Nilsson, Thomas Laurell, James P LandersAbstract:Forensic DNA Analysis of samples obtained from sexual assault evidence relies on separation of male and female components of the recovered genetic material. The conventional separation method used by crime laboratories, differential extraction (DE), is one of the most time-consuming sample preparation steps, requires extensive sample handling, is difficult to automate, and often results in inefficient separation of female DNA from the male sample components. To circumvent conventional DE, acoustic differential extraction (ADE) Analysis was developed on a microfluidic device. The ADE method relies on acoustic trapping of sperm cells in the presence of epithelial cell lysate (which is unretained), and laminar flow valving to direct the male and female fractions to separate outlets. Following the separation of sperm from epithelial cell lysate, DNA extraction, quantitation, amplification, and separation were performed using conventional laboratory methods. The results show that highly purified male and femal...
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acoustic differential extraction for Forensic Analysis of sexual assault evidence
Analytical Chemistry, 2009Co-Authors: Jessica V Norris, Mikael Evander, Katie M Horsmanhall, Johan Nilsson, Thomas Laurell, James P LandersAbstract:Forensic DNA Analysis of samples obtained from sexual assault evidence relies on separation of male and female components of the recovered genetic material. The conventional separation method used by crime laboratories, differential extraction (DE), is one of the most time-consuming sample preparation steps, requires extensive sample handling, is difficult to automate, and often results in inefficient separation of female DNA from the male sample components. To circumvent conventional DE, acoustic differential extraction (ADE) Analysis was developed on a microfluidic device. The ADE method relies on acoustic trapping of sperm cells in the presence of epithelial cell lysate (which is unretained), and laminar flow valving to direct the male and female fractions to separate outlets. Following the separation of sperm from epithelial cell lysate, DNA extraction, quantitation, amplification, and separation were performed using conventional laboratory methods. The results show that highly purified male and female fractions can be obtained with the ADE microdevice from mock sexual assault samples in 14 min. ADE Analysis provides the potential to significantly alter the means by which sexual assault evidence is processed in crime laboratories.
Peter Rådström - One of the best experts on this subject based on the ideXlab platform.
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validation guidelines for pcr workflows in bioterrorism preparedness food safety and Forensics
Accreditation and Quality Assurance, 2018Co-Authors: Johannes Hedman, Moa Lavander, Emelie Näslund Salomonsson, Tomas Jinnerot, Lina Boiso, Bertil Magnusson, Peter RådströmAbstract:The polymerase chain reaction (PCR) is the backbone of contemporary DNA/RNA Analysis, ideally enabling detection of one or just a few target molecules. However, when analysing food or Forensic samples the analytical procedure is often challenged by low amounts of poor quality template molecules and complex matrices. Applying optimised and validated methods in all steps of the Analysis workflow, i.e. sampling, sample treatment, DNA/RNA extraction and PCR (including reverse transcription for RNA Analysis), is thus necessary to ensure the reliability of Analysis. In this paper, we describe how in-house validation can be performed for the different modules of the diagnostic PCR process, providing practical examples as tools for laboratories in their planning of validation studies. The focus is Analysis of heterogeneous samples with interfering matrices, with relevance in food testing, Forensic DNA Analysis, bioterrorism preparedness and veterinary medicine. Our objective is to enable rational in-house validation for reliable and swift quality assurance when results are urgent, for example in the event of a crisis such as a foodborne outbreak or a crime requiring the Analysis of a large number of diverse samples. To that end, we explain the performance characteristics associated with method validation from a PCR and biological sample matrix perspective and suggest which characteristics to investigate depending on the type of method to be validated. Also, we include a modular approach to validation within the PCR workflow, aiming at efficient validation and a flexible use of methods. (Less)
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a panel of pcr inhibitory reference materials for quality evaluation of multiplex str Analysis kits
Forensic Science International: Genetics Supplement Series, 2015Co-Authors: Malin Sanga, Lina Boiso, Peter Rådström, Ricky Ansell, Harwati Lindsten, Johannes HedmanAbstract:PCR inhibition is a critical parameter in Forensic DNA Analysis. Substances interfering with amplification of short tandem repeats (STRs) may generate partial and/or ambiguous DNA profiles. We present a strategy for developing a broad panel of PCR-inhibitory reference materials (RMs), representing common casework samples. Our panel, including solutions prepared from for example cigarettes, chewing gum and soil, is a tool for in-house validation and lot testing of STR systems. PowerPlex ESX 16 Fast System tolerated high levels of some RMs, but several substances caused amplification problems. Humic acid had a negative effect on amelogenin, moist snuff hindered amplification of longer fragments, and chewing gum caused generally lowered allele peak heights. Applying a broad panel of RMs ensures that a wide range of inhibitory substances are tested, giving an improved understanding of inhibitor tolerance and effects.
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synergy between DNA polymerases increases polymerase chain reaction inhibitor tolerance in Forensic DNA Analysis
Analytical Biochemistry, 2010Co-Authors: Johannes Hedman, Anders Nordgaard, Birgitta Rasmusson, Ricky Ansell, Charlotte Dufva, Peter RådströmAbstract:The success rate of diagnostic polymerase chain reaction (PCR) Analysis is lowered by inhibitory substances present in the samples. Recently, we showed that tolerance to PCR inhibitors in crime scene saliva stains can be improved by replacing the standard DNA polymerase AmpliTaq Gold with alternative DNA polymerase-buffer systems (Hedman et al., BioTechniques 47 (2009) 951-958). Here we show that blending inhibitor-resistant DNA polymerase-buffer systems further increases the success rate of PCR for various types of real crime scene samples showing inhibition. For 34 of 42 "inhibited" crime scene stains, the DNA profile quality was significantly improved using a DNA polymerase blend of ExTaq Hot Start and PicoMaxx High Fidelity compared with AmpliTaq Gold. The significance of the results was confirmed by Analysis of variance. The blend performed as well as, or better than, the alternative DNA polymerases used separately for all tested sample types. When used separately, the performance of the DNA polymerases varied depending on the nature of the sample. The superiority of the blend is discussed in terms of complementary effects and synergy between the DNA polymerase-buffer systems.
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improved Forensic DNA Analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles
BioTechniques, 2009Co-Authors: Johannes Hedman, Anders Nordgaard, Birgitta Rasmusson, Ricky Ansell, Peter RådströmAbstract:DNA evidence, linking perpetrators to crime scenes, is central to many legal proceedings. However, DNA samples from crime scenes often contain PCR-inhibitory substances, which may generate blank or incomplete DNA profiles. Extensive DNA purification can be required to rid the sample of these inhibitors, although these procedures increase the risk of DNA loss. Most Forensic laboratories use commercial DNA amplification kits (e.g., AmpFlSTR SGM Plus) with the DNA polymerase AmpliTaq Gold as the gold standard. Here, we show that alternative DNA polymerase-buffer systems can improve the quality of Forensic DNA Analysis and efficiently circumvent PCR inhibition in crime scene samples, without additional sample preparation. DNA profiles from 20 of 32 totally or partially inhibited crime scene saliva samples were significantly improved using Bio-X-Act Short, ExTaq Hot Start, or PicoMaxx High Fidelity instead of AmpliTaq Gold. A statistical model for unbiased quality control of Forensic DNA profiles was developed to quantify the results. Our study demonstrates the importance of adjusting the chemistry of the PCR to enhance Forensic DNA Analysis and diagnostic PCR, providing an alternative to laborious sample preparation protocols.
Johannes Hedman - One of the best experts on this subject based on the ideXlab platform.
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Determining the optimal Forensic DNA Analysis procedure following investigation of sample quality
International Journal of Legal Medicine, 2018Co-Authors: Ronny Hedell, Johannes Hedman, Petter MostadAbstract:Crime scene traces of various types are routinely sent to Forensic laboratories for Analysis, generally with the aim of addressing questions about the source of the trace. The laboratory may choose to analyse the samples in different ways depending on the type and quality of the sample, the importance of the case and the cost and performance of the available Analysis methods. Theoretically well-founded guidelines for the choice of Analysis method are, however, lacking in most situations. In this paper, it is shown how such guidelines can be created using Bayesian decision theory. The theory is applied to Forensic DNA Analysis, showing how the information from the initial qPCR Analysis can be utilized. It is assumed the alternatives for Analysis are using a standard short tandem repeat (STR) DNA Analysis assay, using the standard assay and a complementary assay, or the Analysis may be cancelled following quantification. The decision is based on information about the DNA amount and level of DNA degradation of the Forensic sample, as well as case circumstances and the cost for Analysis. Semi-continuous electropherogram models are used for simulation of DNA profiles and for computation of likelihood ratios. It is shown how tables and graphs, prepared beforehand, can be used to quickly find the optimal decision in Forensic casework.
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validation guidelines for pcr workflows in bioterrorism preparedness food safety and Forensics
Accreditation and Quality Assurance, 2018Co-Authors: Johannes Hedman, Moa Lavander, Emelie Näslund Salomonsson, Tomas Jinnerot, Lina Boiso, Bertil Magnusson, Peter RådströmAbstract:The polymerase chain reaction (PCR) is the backbone of contemporary DNA/RNA Analysis, ideally enabling detection of one or just a few target molecules. However, when analysing food or Forensic samples the analytical procedure is often challenged by low amounts of poor quality template molecules and complex matrices. Applying optimised and validated methods in all steps of the Analysis workflow, i.e. sampling, sample treatment, DNA/RNA extraction and PCR (including reverse transcription for RNA Analysis), is thus necessary to ensure the reliability of Analysis. In this paper, we describe how in-house validation can be performed for the different modules of the diagnostic PCR process, providing practical examples as tools for laboratories in their planning of validation studies. The focus is Analysis of heterogeneous samples with interfering matrices, with relevance in food testing, Forensic DNA Analysis, bioterrorism preparedness and veterinary medicine. Our objective is to enable rational in-house validation for reliable and swift quality assurance when results are urgent, for example in the event of a crisis such as a foodborne outbreak or a crime requiring the Analysis of a large number of diverse samples. To that end, we explain the performance characteristics associated with method validation from a PCR and biological sample matrix perspective and suggest which characteristics to investigate depending on the type of method to be validated. Also, we include a modular approach to validation within the PCR workflow, aiming at efficient validation and a flexible use of methods. (Less)
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a panel of pcr inhibitory reference materials for quality evaluation of multiplex str Analysis kits
Forensic Science International: Genetics Supplement Series, 2015Co-Authors: Malin Sanga, Lina Boiso, Peter Rådström, Ricky Ansell, Harwati Lindsten, Johannes HedmanAbstract:PCR inhibition is a critical parameter in Forensic DNA Analysis. Substances interfering with amplification of short tandem repeats (STRs) may generate partial and/or ambiguous DNA profiles. We present a strategy for developing a broad panel of PCR-inhibitory reference materials (RMs), representing common casework samples. Our panel, including solutions prepared from for example cigarettes, chewing gum and soil, is a tool for in-house validation and lot testing of STR systems. PowerPlex ESX 16 Fast System tolerated high levels of some RMs, but several substances caused amplification problems. Humic acid had a negative effect on amelogenin, moist snuff hindered amplification of longer fragments, and chewing gum caused generally lowered allele peak heights. Applying a broad panel of RMs ensures that a wide range of inhibitory substances are tested, giving an improved understanding of inhibitor tolerance and effects.
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synergy between DNA polymerases increases polymerase chain reaction inhibitor tolerance in Forensic DNA Analysis
Analytical Biochemistry, 2010Co-Authors: Johannes Hedman, Anders Nordgaard, Birgitta Rasmusson, Ricky Ansell, Charlotte Dufva, Peter RådströmAbstract:The success rate of diagnostic polymerase chain reaction (PCR) Analysis is lowered by inhibitory substances present in the samples. Recently, we showed that tolerance to PCR inhibitors in crime scene saliva stains can be improved by replacing the standard DNA polymerase AmpliTaq Gold with alternative DNA polymerase-buffer systems (Hedman et al., BioTechniques 47 (2009) 951-958). Here we show that blending inhibitor-resistant DNA polymerase-buffer systems further increases the success rate of PCR for various types of real crime scene samples showing inhibition. For 34 of 42 "inhibited" crime scene stains, the DNA profile quality was significantly improved using a DNA polymerase blend of ExTaq Hot Start and PicoMaxx High Fidelity compared with AmpliTaq Gold. The significance of the results was confirmed by Analysis of variance. The blend performed as well as, or better than, the alternative DNA polymerases used separately for all tested sample types. When used separately, the performance of the DNA polymerases varied depending on the nature of the sample. The superiority of the blend is discussed in terms of complementary effects and synergy between the DNA polymerase-buffer systems.
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improved Forensic DNA Analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles
BioTechniques, 2009Co-Authors: Johannes Hedman, Anders Nordgaard, Birgitta Rasmusson, Ricky Ansell, Peter RådströmAbstract:DNA evidence, linking perpetrators to crime scenes, is central to many legal proceedings. However, DNA samples from crime scenes often contain PCR-inhibitory substances, which may generate blank or incomplete DNA profiles. Extensive DNA purification can be required to rid the sample of these inhibitors, although these procedures increase the risk of DNA loss. Most Forensic laboratories use commercial DNA amplification kits (e.g., AmpFlSTR SGM Plus) with the DNA polymerase AmpliTaq Gold as the gold standard. Here, we show that alternative DNA polymerase-buffer systems can improve the quality of Forensic DNA Analysis and efficiently circumvent PCR inhibition in crime scene samples, without additional sample preparation. DNA profiles from 20 of 32 totally or partially inhibited crime scene saliva samples were significantly improved using Bio-X-Act Short, ExTaq Hot Start, or PicoMaxx High Fidelity instead of AmpliTaq Gold. A statistical model for unbiased quality control of Forensic DNA profiles was developed to quantify the results. Our study demonstrates the importance of adjusting the chemistry of the PCR to enhance Forensic DNA Analysis and diagnostic PCR, providing an alternative to laborious sample preparation protocols.