Browsing by Subject "forensic science"
Now showing 1 - 7 of 7
- Results Per Page
- Sort Options
Item Evaluating Noise and the Implications of Methodology in the Analytical Threshold Designation for Forensic Genetic Analysis(2015-08-01) Malone, Ashley N.; Joseph E. Warren; John V. Planz; Raghu R. KrishnamoorthyIt is common in the forensic science community to have standardization and uniformity in all laboratory processes. The method for the determination of a minimum detection threshold or synonymously an analytical threshold for genetic analysis is not uniform across forensic labs. Variation amongst the methods in DNA testing by forensic laboratories leads to variations in the results of the DNA testing. The results of this study show a method using DNA sample types versus non-DNA sample types will better reflect the effects of baseline noise that may be encountered in forensic casework samples. In addition, there is a need for a calculation method to be designated as an appropriate tool in determining analytical thresholds. More studies on baseline noise and methods in distinguishing analytical thresholds will help in the determination of the most appropriate calculation method to be used across all forensic laboratories.Item Internal Validation of the AmpFlSTR® Identifiler™ PCR Amplification Kit at The Forensic Testing Laboratory, Inc.(2009-08-01) Lowe, Cheryl M.; Warren, Joseph E.Prior to being implemented into forensic casework at a laboratory, a new method or product used in forensic DNA analysis must be validated internally within that laboratory. An internal validation of the AmpFlSTR® Identifiler™ PCR Amplification Kit at The Forensic Testing Laboratory was conducted, and it consisted of a sensitivity study, mixture study, non-probative case sample study, precision study, and a contamination study. The sensitivity study served to determine the target amount of input DNA to be added to each reaction, and the mixture study demonstrated how sensitive this kit is in detecting mixed source samples. The non-probative case sample study simulated various types of samples that may occur in casework. The results of each study are satisfactory for an internal validation, and the AmpFlSTR® Identifiler™ PCR Amplification Kit may now be used in forensic casework, since the kit was proven to be reliable, robust, and reproducible.Item Internal Validation Study of Promega's Powerplex Y System(2004-08-01) Donovan, Erin W.; Joseph Warren; John Planz; Arthur EisenbergThe expectations of this validation study and results obtained are similar. For the sensitivity study, Promega documents the optimal amount of DNA to be added to the PCR reaction 500pg to lng, (11) which is consistent with the results of this validation study. For the mixture study of male and female DNA Promega claims up to a concentration [greater than] 100X female DNA compared to male DNA is acceptable with no effects. This was the case in the validation study, which had a proportion of 1:50 with no effect. The substrate study showed leather to inhibit the PowerPlex Y System which has been see to happen in other DNA testing (11). The environmental study test showed humidity effects the results of the PowerPlex Y system. Also this frequently has been in other DNA testing due to the humidity causing DNA degradation, which results in a partial profile or no results for that sample. The results obtained from this internal validation study can be compared to other validation studies for Y chromosome specific STR multiplex systems. For example the paper “Validation and casework application a Y Chromosome specific STR multiple” written by Mechthild Prinz is comparable to that of this validation study performed (3). The Y-STR multiplex tested only four loci versus the PowerPlex Y System which tests twelve. The studies addressed in each of the validation studies consist of mixture, sensitivity, environmental, and substrate. For the male-female mixture study, the female DNA had no effect on the results up to 1:4000 ratios. These results are similar to the Powerplex Y System because no effect on the ability to obtain a full profile with a mixed sample of female and male DNA was observed. The sensitivity for the multiplex system showed allelic drop out at 125ph of DNA and optimal amount of DNA at 1-2ng. The PowerPlex Y System showed allelic drop out at 250ph and optimal amount of DNA to be 500pg-1ng. The environmental studies were similar because both showed allelic drop out for the humidity conditions. The multiplex with four loci did not use leather as a substrate, the other substrates were similar in both validation studies and reported similar results. Validation studies are frequently needed in order to validate a technique to be used in a forensic laboratory. Forensic cases are frequently under scrutiny by the judicial system. The questions due not lie in the science behind DNA testing but rather the process by which a laboratory performs the DNA test. In order to reduce the amount of questions validation studies are performed and interpretation guidelines are developed from those validation studies. Interpretation guidelines are written to direct and assist an analyst in making a final interpretation of each individual sample. The guidelines consist of the control, which must be run alongside each sample with the excepted results of each of the controls. The guidelines include types of identification for a sample such as no result, inconclusive, exclusive, and not excluded. Also DNA quantification information is included along with internal lane standard and allelic ladder guidelines. Interpretations of mixtures are included, which explains peak height ratios and how to determine a mixed sample. A calculation section is included to address the appropriate calculations to be used with the system to analyze the results. Interpretation guidelines will be pronounced based on this validation study for the University of North Texas Health Science DNA Identity laboratory.Item Optimization of Filter Metrics for Mitochondrial DNA Sequence Analysis.(2009-08-01) Musslewhite, Pamela; Planz, John V.Quality metrics translate sequence information into numerical values which allows a software program to filter through data without human intervention. Primer specific settings for the trace score and contiguous read length in Sequence Scanner Software v1.0 (Applied Biosystems, Foster City, CA) were established using a calibration dataset of 2,817 sequence traces and validated using a second dataset of 5,617 sequence traces. Prior to optimization 51.7% of the samples required manual intervention while 28.4% require review after optimization. An evaluation of signal intensity and signal to noise ratio variables was performed and no trend was recognized for predictive modeling. Use of quality values per peak to ascertain confidence in the base call was evaluated and found to be a feasible parameter for sample quality assessment and confident base calling.Item The Validation of Applied Biosystems Quantifiler Human DNA Quantification Kit and Quantifiler Y Human Male DNA Quantification Kit for the Armed Forces DNA Identification Laboratory(2004-08-01) Levandowsky, Elizabeth C.; Arthur Eisenberg; Joseph Warren; John PlanzLevandowsky, Elizabeth C., The Validation of Applied Biosystems Quantifiler™ Human DNA Quantification Kit and Quantifier™ Y Human Male DNA Identification Kit for the Armed Forces DNA Identification Laboratory. Master of Science (Forensic Genetics), July 2004. 14 tables, 6 figures, references, 12 titles. To produce the most accurate and reliable results, forensic laboratories, such as AFDIL, must examine new technologies in the field of DNA analysis. The present study is the beginning of an internal validation of the most recent development in DNA quantitation, RT-PCR. The Quantifiler Human DNA Quantification Kit and Quantifiler Y Human Male DNA Identification Kit are RT-PCR assays that quantitate human and male DNA, and detect PCR inhibitors which may hinder the ability to produce a reliable STR profile. Sensitivity and non-probative case sample studies were performed according to the DAB guidelines. The Quantifiler kits were not as sensitive as had been previously reported by Applied Biosystems. The non-probative case sample study demonstrated results two fold greater than results from the Taqman® Alu-PCR Quantitation System, a RT-PCR assay developed and validated at AFDIL. At this time, it appears it may be in the best interest of AFDIL to continue its use of the Taqman® Alu-PCR Quantitation System.Item Validation of Genemapper ID Human Identification Software for Forensic STR DNA Analysis(2005-12-01) Capt, Christina L.; John Planz; Arthur Eisenberg; Joseph WarrenCapt, Christina L., Validation of GeneMapper ID Human Identification Software for Forensic STR DNA Analysis. Master of Science (Forensic Genetics), December, 2005, 73 pp., 5 tables, 12 figures, references, 6 titles. ABI GeneMapper ID analysis software replaces and combines both GeneScan and Genotyper data analysis programs. Fragment sizing and allele typing functions are performed in a single analysis, and the software includes data quality assessment features not available with previous software packages. The software was directly compared to the current laboratory STR data analysis software, GeneScan and Genotyper. All peaks evaluated with GeneMapper ID exhibited lower peak heights that their GeneScan/Genotyper analysis counterparts. A mean percent decrease in peak height of 3.8% ± 0.9% was observed for all peaks greater than 500rfu. Observed stutter ratios were comparable to the default stutter filter settings of GeneMapper ID. Parallel analyses of 388 sample files resulted in absolute concordance for all reference samples and most evidentiary samples. The software performed better than GeneScan/Genotyper in labeling microvariants, baselining data, disregarding –A peaks, aligning below threshold data, and defining size standard peaks despite artifact interference. The Off Scale and Spectral Pull-up PQV did not function as expected for sizing and genotyping STR fragments for forensic human identification analysis.Item Validation of HemaSpotTM devices for the collection and long-term, room temperature storage of biological fluids from forensic reference samples(2019-05) Gonzalez, Kimberly A.; Warren, Joseph E.; Planz, John V.; Gaydosh-Combs, Laura; Maddux, Scott D.As forensic DNA samples spend more time in storage, collection devices capable of long-term, room temperature preservation provide cost-effective solutions. This project evaluated two different HemaSpot(TM) cartridges for collecting and storing human bodily fluids. Sensitivity was assessed by spotting five different volumes of blood and saliva from two individuals. Stability was examined by storing the sample collection membranes at 100 degrees C to simulate long-term storage. After 24 hours, DNA was extracted from eight 1.2-mm punches, quantified, amplified, and categorized by STR locus. Exposure to elevated temperature resulted in degradation based on quantification quality indicators and electropherogram results. Despite these observations, full STR profiles were obtained for the majority of sensitivity and stability samples. HemaSpotTM devices demonstrate potential in forensic applications for stabilizing reference DNA samples.