PENDULUM--a guideline-based approach to the interpretation of STR mixtures

Several years ago, a theory to interpret mixed DNA profiles was proposed that included a consideration of peak area using the method of least squares. This method of mixture interpretation has not been widely adopted because of the complexity of the associated calculations. Most reporting officers (RO) employ an experience and judgement based approach to the interpretation of mixed DNA profiles. Here we present an approach that has formalised the thinking behind this experience and judgement. This has been written into a computer program package called PENDULUM. The program uses a least squares method to estimate the pre-amplification mixture proportion for two potential contributors. It then calculates the heterozygous balance for all of the potential sets of genotypes. A list of "possible" genotypes is generated using a set of heuristic rules. External to the programme the candidate genotypes may then be used to formulate likelihood ratios (LR) that are based on alternative casework propositions. The system does not represent a black box approach; rather it has been integrated into the method currently used by the reporting officers at the Forensic Science Service (FSS). The time saved in automating routine calculations associated with mixtures analysis is significant. In addition, the computer program assists in unifying reporting processes, thereby improving the consistency of reporting.     

Validation of a 21-locus autosomal SNP multiplex for forensic identification purposes

A single nucleotide polymorphism (SNP) multiplex has been developed to analyse highly degraded and low copy number (LCN) DNA template, i.e. <100 pg, for scenarios including mass disaster identification. The multiplex consists of 20 autosomal non-coding loci plus Amelogenin for sex determination, amplified in a single tube PCR reaction and visualised on the Applied Biosystems 3100 capillary electrophoresis (CE) system. Allele-specific primers tailed with shared universal tag sequences were designed to speed multiplex design and balance the amplification efficiencies of all loci through the use of a single reverse and two differentially labelled allele denoting forward universal primers. As the multiplex is intended for use with samples too degraded for conventional profiling, a computer program was specifically developed to aid interpretation. Critical factors taken into account by the software include empirically determined extremes of heterozygous imbalance (Hb) and the drop-out threshold (Ht) defined as the maximum peak height of a surviving heterozygous allele, where its partner may have dropped out. The discrimination power of the system is estimated at 1 in 4.5 million, using a White Caucasian population database. Comparisons using artificially degraded samples profiled with both the SNP multiplex and AMPFISTR SGM plus (Applied Biosystems) demonstrated a greater likelihood of obtaining a profile using SNPs for certain sample types. Saliva stains degraded for 147 days generated an 81% complete SNP profile whilst short tandem repeats (STRs) were only 18% complete; similarly blood degraded for 243 days produced full SNP profiles but only 9% with STRs. Reproducibility studies showed concordance between SNP profiles for different sample types, such as blood, saliva, semen and hairs, for the same individual, both within and between different DNA extracts.     

A re-examination of the MMPI-2 aggressiveness and immaturity indices in law enforcement screening

This study reports an analysis of Bartol's (1991) Immaturity Index and Hargrave and associates' (1988) Aggressiveness Index as a measure of police conduct. The correlations between the supervisory ratings and the Immaturity and Aggressiveness indices were examined for 1020 law enforcement officers. The results showed that Immaturity Index was related to termination for failure to complete training and insubordination. The Aggressiveness Index was related to a termination for failure to complete training and several other problematic police behaviors, but was not found to be specifically linked with acts of aggression. Implications for using these two indices in law enforcement selection are discussed. Authors' Note: Cary Rostow, Ph.D. is president of Matrix, Inc., Baton Rouge, Louisiana, and is in private practice in Baton Rouge. Robert Davis, Ph.D., is executive vice-president and director of science, research, and development for Matrix, Inc., and has a private practice in Baton Rouge. James B. Pinston, Ph.D., is a clinical neuropsychologist within the department of neurology at the Louisiana State University Health Sciences Center and School of Medicine in Shreveport, Louisiana. Dennis R. Combs, Ph.D., is an assistant professor of psychology at the University of Tulsa. Dennis R. Dixon, M.A., is currently a doctoral student at Louisiana State University.     

Development of a finger printing device for use on a mobile robot

In this paper, we describe the development of a device for fuming fingerprints with cyanoacrylate (Super Glue) to enable police tactical units to obtain fingerprint evidence from suspicious packages using a remote-controlled robot. Through a series of initial experiments and preliminary designs, we show that effective cyanoacylate fuming requires sufficient heat, humidity, and airflow. This work led to the development of a final working prototype, called robot accessory for fuming fingerprint evidence (RAFFE), which is currently being field tested by the Calgary Police Service.     

The Benefit Equity Principle and Willingness to Pay for City Services

In 1991 and 1992, the City of Eugene, Oregon engaged in a citizen participation process to determine public support for a variety of spending and budget balancing alternatives. This process, called Eugene Decisions, employed an innovative combination of public forums, budget balancing exercises and representative surveys. Two of the surveys, which included questions about individual service use, are analyzed here in order to test whether the use of city services is related to willingness to pay taxes and fees. The concept of benefit equity is supported if service use is positively associated with willingness to pay.