Comparison of Decision Tree and Logistic Regression Models for Utilization in Sexual Assault Kit Processing.

To combat the influx of sexual assault kits (SAKs) that need to be tested, an exploration of data from Ohio's SAK Testing Initiative was carried out to identify variables that impact whether a SAK contains a probative DNA profile that is eligible for the Combined DNA Index System (CODIS) database. A validation study was completed to confirm the existence of variable relationships from the initial examination of data; new and modified statistical models were introduced to improve the predictive accuracy to determine if a SAK will contain at least one CODIS eligible DNA profile. Descriptive statistics from the validation data set confirmed conclusions about the effects of days between the assault and kit collection, the age of the victim, and consensual sex around the time of the kit collection for obtaining CODIS eligibility of DNA. The decision tree was selected as the best model.

Statistical Modeling of the Case Information From the Ohio Attorney General's Sexual Assault Kit Testing Initiative.

The Ohio Attorney General's Sexual Assault Kit (SAK) Testing Initiative has resulted in nearly 14,000 kits being processed since the initiation of the project in 2012. A logistic regression model was fit to the data from 2500 SAKs in order to determine the probability of obtaining at least one Combined DNA Index System (CODIS) eligible DNA profile based on a number of predictor variables. The probability of obtaining at least one CODIS eligible DNA profile from an SAK varied as a function of (i) days to kit collection following a sexual assault; (ii) years to kit submission to the laboratory for testing following kit collection; (iii) the age of the victim; and (iv) the occurrence of victim-reported consensual sex around the time of the assault and/or kit collection. These findings demonstrate the utility of the statistical modeling of data obtained from the "forklift" testing approach of sexual assault kits.

Development of a human-specific real-time PCR assay for the simultaneous quantitation of total genomic and male DNA.

A duplex real-time quantitative PCR assay was developed for forensic DNA analysis, which provides simultaneous quantitation of total genomic human DNA and human male DNA. The assay utilizes two spectrally resolved fluorogenic probes in a 5' nuclease (TaqMantrade mark) assay. Within the range of organisms empirically tested and based upon theoretical specificity using National Center for Biotechnology Information GenBank sequences, primer and probe sequences were shown to be human specific, and the Y-chromosome probe, male-specific. A mixture-challenge study resulted in accurate quantitation of 25 pg male DNA in a mixture of up to 1:5000 (male:female DNA). Additional experimental results include comparisons with the slot blot method and commercial real-time PCR kits. The assay developed addresses the shortcomings of the traditional slot blot method as well as the commercial real-time PCR kits. This method is shown to be specific, relatively simple, rapid, has low limits of detection, and consumes limited sample in addition to reporting both the male and total genomic DNA concentrations present.