Bounding the number of contributors to mixed DNA stains

We derive a simple inequality for the probability of observing a given DNA profile when assuming a fixed number of unknown persons have contributed to the mixed stain. We then show how this inequality can be used to obtain an upper bound for the number of unknown contributors needed to be considered.     

Bounding the number of contributors to mixed DNA stains

We derive a simple inequality for the probability of observing a given DNA profile when assuming a fixed number of unknown persons have contributed to the mixed stain. We then show how this inequality can be used to obtain an upper bound for the number of unknown contributors needed to be considered.     

About the authors

In recent years, afterschool programs have received support for their potential to reduce juvenile delinquency and victimization. This support stems largely from reports based on police incident data indicating that juvenile crime and victimization peak during the afterschool hours. However, prior studies of victimization surveys and self‐reports of crime suggest that delinquency is more elevated during school hours. Utilizing self‐report data from a sample of juveniles participating in an evaluation of afterschool programs in Maryland, this study shows that juvenile victimization and delinquency peak during the school hours, while substance use peaks during the weekend. Disaggregating by offense reveals, however, that the more serious violent offenses are elevated during the afterschool hours, while simple assault offenses are most elevated during school hours. Implications for research and practice are discussed.     

About the authors

We have reached what may be an important turning point in the development of criminological thought and of social policy toward crime. The “conservative revolution” in criminology has lost considerable credibility, along with the entire set of minimalist strategies toward the disadvantaged that dominated social policy throughout much of the recent past. A space has opened for the development of a “social environmental” or “human-ecological” approach to crime, which combines a variety of interventions on the individual and family level with an array of broader policies aimed at controlling the social and economic forces that place individuals, families, and communities at risk in the first place.     

About the authors

The present research evaluates the hypothesis that dimensions of police organizational structure germane to police reformers may be affected by the dynamics of organizational size and urbanism, thus constraining the ability of reformers to invoke desired structural changes. Using data gathered from police departments in Illinois, we examined the impact of urbanism and size on four dimensions of agency structure of interest to advocates of police reform: concentration, height or segmentation, civilianization, and supervisory ratio. Size revealed both linear and nonlinear influences on two dimensions of structure. This finding suggests that research on factors affecting organizational structure, typically conducted in large departments, may not generalize to smaller agencies. The authors concluded that the influence of size, though affecting dimensions of organizational structure, was generally too modest to substantially constrain structural variation.