Risk Aversion, Liability Rules, and Safety

This paper investigates the performance of liability rules in two-party stochastic externality problems where negotiations are feasible and side payments are based on the realized level of externalities. Results show that an increase in polluter liability does not necessarily increase safety or efficiency in cases where the polluter is risk neutral. Complete polluter liability is found to yield Pareto optimality. When either party is risk averse, an increase in polluter liability may sometimes reduce safety and efficiency. If the polluter is risk neutral and the victim is risk averse, Pareto optimality is only achieved by assigning full liability on the polluter, i.e. giving the victim complete property rights to a clean environment. If the polluter is risk averse and the victim is risk neutral, no level of polluter liability is optimal. In this case, optimality can only be achieved through a contract on abatement activities, such that the risk-averse polluter receives a guaranteed payment regardless of the stochastic outcome.     

Characterization of human DNA in environmental samples

Environmental samples from indoor surfaces can be confounded by dust, which is composed largely of human skin cells and has been documented to contain roughly tens of micrograms of total DNA per gram of dust. This study complements previous published work by providing estimates of the quantity of amplifiable human DNA found in environmental samples from a typical indoor environment, categorized by the intensity of human traffic and visible quantity of dust. Dust was collected by surface swabbing standard 576 cm² areas in eight locations, and evaluated for total DNA quantity, presence of human DNA (mitochondrial and nuclear loci using conventional PCR), quantity of human nuclear DNA using quantitative PCR, and STR analysis. The total DNA content of 36 dust samples ranged from 9 to 28 ng/cm², and contained 0.2–1.1 pg/cm² of human DNA. Overall, human DNA was detected in 97% of 36 dust samples and 61% of samples yielded allele distributions of varying degrees of complexity when subjected to STR analysis. The implications of this study are twofold. First, the presence of dust in evidence can be a significant contamination source in forensic investigations because the human DNA component is of sufficient quality and quantity to produce allele calls in STR analysis. This can be effectively managed by implementing stringent protocols for collection and analysis of potential biological samples. A second implication is the use of dust as a source of evidence for identification of inhabitants within a defined location. In the latter case, a number of additional studies would be necessary to identify relevant pretreatments for environmental dust samples and to develop the necessary deconvolution techniques to separate the composite genotypes obtained.     

DNA typing in populations of mule deer for forensic use in the Province of Alberta

The present study involves the development of forensic DNA typing tests and databases for mule deer in the Province of Alberta. Two multiplex PCR reactions interrogating 10 loci were used to analyze samples from three populations of mule deer. Additionally, an amelogenin based sex-typing marker was used to determine the gender of samples. Results show that the tests and databases are appropriate for use in forensic applications. Additionally, the results indicate that there is little population structure in mule deer in Alberta and that no changes to management of this game species are suggested.     

The Wanderers

Dr. Jeffreys writes to say that he would be interested to hearof any other tribe whose name is a sobriquet for "wanderer"or "stranger". He has not dealt with Southern Africa, and wewould therefore suggest Angoni. Any reader who can add to thelist may care to get into touch with the writer of this articleat Bamenda, British Cameroons.