Results of a proposed breath alcohol proficiency test program

Although proficiency test programs have long been used in both clinical and forensic laboratories, they have not found uniform application in forensic breath alcohol programs. An initial effort to develop a proficiency test program appropriate to forensic breath alcohol analysis is described herein. A total of 11 jurisdictions participated in which 27 modern instruments were evaluated. Five wet bath simulator solutions with ethanol vapor concentrations ranging from 0.0254 to 0.2659 g/210 L were sent to participating programs, instructing them to perform n = 10 measurements on each solution using the same instrument. Four of the solutions contained ethanol only and one contained ethanol mixed with acetone. The systematic errors for all instruments ranged from -11.3% to +11.4% while the coefficient of variations ranged from zero to 6.1%. A components-of-variance analysis revealed at least 79% of the total variance as being due to the between-instrument component for all concentrations. Improving proficiency test program development should consider: (1) clear protocol instructions, (2) frequency of proficiency testing, (3) use lower concentrations for determining limits-of-detection and -quantitation, etc. Despite the lack of a biological component, proficiency test participation should enhance the credibility of forensic breath test programs.     

A Grass Molecular Identification System for Forensic Botany: A Critical Evaluation of the Strengths and Limitations*

Abstract: Plant material is frequently encountered in criminal investigations but often overlooked as potential evidence. We designed a DNA‐based molecular identification system for 100 Australian grasses that consisted of a series of polymerase chain reaction assays that enabled the progressive identification of grasses to different taxonomic levels. The identification system was based on DNA sequence variation at four chloroplast and two mitochondrial loci. Seventeen informative indels and 68 single‐nucleotide polymorphisms were utilized as molecular markers for subfamily to species‐level identification. To identify an unknown sample to subfamily level required a minimum of four markers or nine markers for species identification. The accuracy of the system was confirmed by blind tests. We have demonstrated “proof of concept” of a molecular identification system for trace botanical samples. Our evaluation suggests that the adoption of a system that combines this approach with DNA sequencing could assist the morphological identification of grasses found as forensic evidence.     

A Cannabis sativa STR Genotype Database for Australian Seizures: Forensic Applications and Limitations*

Abstract: A genetic database was established with the aim of documenting the genetic diversity of Cannabis sativa in Australia for future utilization in forensic investigations. The database consisted of genotypes at 10 validated short tandem repeat loci for 510 plants representing drug seizures from across Australia and 57 fiber samples. A total of 106 alleles and 314 different genotypes were detected. All fiber samples exhibited unique genotypes while 55% of the drug samples shared a genotype with one or more samples. Shared genotypes were mostly found within seizures; however, some genotypes were found among seizures. Statistical analysis indicated that genotype sharing was a consequence of clonal propagation rather than a lack of genetic resolution. Thus, the finding of shared genotypes among seizures is likely due to either a common supplier, or direct links among seizures. Notwithstanding the potential intelligence information provided by genetic analysis of C. sativa, our database analysis also reveals some present limitations.     

Neighborhood Cultural Heterogeneity and Adolescent Violence

A small number of scholars have attempted to reorient current thinking about the way cultural effects operate in poor neighborhoods. Scholars argue that socioeconomic disadvantage fosters heterogeneity in cultural models. Moreover, cultural heterogeneity theoretically plays an important role in shaping adolescent decision-making in poor neighborhoods, including decisions related to violent behavior. We test these assumptions using multilevel data comprised of a sample of African-American adolescents. Our findings lend support to these arguments. In particular, the results suggested that neighborhood structural disadvantage increases the degree of disagreement or heterogeneity regarding the inappropriateness of violence. Further, exposure to cultural heterogeneity increased adolescents?? involvement in violent behavior and had a moderating influence on the link between individual frames and adolescent violent behavior.