Laser microdissection separation of pure spermatozoa from epithelial cells for short tandem repeat analysis

Short tandem repeat (STR) analysis is a valuable tool in identifying the source of biological stains, particularly from the investigation of sexual assault crimes. Difficulties in analysis arise primarily in the interpretation of mixed genotypes when cell separation of the sexual assailant's sperm from the victim's cells is incomplete. The forensic community continues to seek improvements in cell separation methods from mixtures for DNA typing. The feasibility of applying laser microdissection (LMD) technology to precisely separate sexual assault cell mixtures by visual inspection coupled with laser dissection was assessed through three experiments. First, various histological stains were evaluated for use with LMD and DNA analysis. Second, different DNA isolation methods were evaluated on LMD-collected cells. Finally, STR analysis was performed on LMD-separated sperm cells from mixtures of semen and female buccal epithelial cells. The results indicated (a) hematoxylin/eosin staining performed best in its ability to differentiate sperm and epithelial cells while exhibiting the least negative effect on further downstream analysis; (b) both QIAamp and Lyse-N-Go methods were useful for recovery of DNA from LMD-collected sperm cells; and (c) LMD separation provided clear STR profiles of the male donor with the absence of any additional alleles from the female donor. This report describes an efficient, low-manipulation LMD method for the efficient separation of spermatozoa from two-donor sperm/epithelial cell mixtures.     

The feasibility of external blind DNA proficiency testing. II. Experience with actual blind tests

The background and goals of a national study to determine the feasibility of blind proficiency testing in U.S. forensic DNA laboratories are discussed. Part of the project involved designing and executing a series of fifteen blind proficiency tests. Execution included biological specimen donor recruitment and case evidence manufacturing. Simulated cases were submitted to DNA laboratories by law enforcement agencies and in some cases by other forensic-science laboratories. Replicate-manufactured evidence was submitted to reference laboratories to simulate the workings of a larger-scale program. Ten tests were straightforward, and essentially tested analytical ability. Five tests involved selecting on the basis of case facts appropriate bloodstains for typing from a bloodstain pattern. We describe in detail our experience in designing and conducting these blind proficiency test trials, and relate those experiences to the overall issue of blind proficiency testing as a quality-assurance tool in forensic DNA laboratories. In this feasibility test series, one blind test was detected by a laboratory, a second one was shown to the lab by law enforcement, and a third was never completed because of lapses in communication. Turnaround times were relatively fast in the independent/commercial labs and relatively slow in the larger public laboratories. Two cross-state case-to-case CODIS "hits" were "planted" among the first series of ten blind tests. One pair was detected. One member of the second pair went to a lab that was not CODIS-ready.     

Congressional Response to Mandate Elections

Elections from time to time are widely believed to carry a mandate, to express a message about changed policy preferences of the electorate. Whatever the accuracy of such beliefs—a matter about which we are skeptical—perceptions of a mandate should affect the behavior of actors in government. Politicians lack the scholarly luxury of waiting for careful analyses. They must act in the months following elections. We postulate that many will act as if the mandate perceptions were true, veering away from their normal voting patterns. This is driven by election results and interpretations that undermine old calculations about what voters want. As the flow of information gradually changes these perceptions, and the election becomes more distant, members of Congress return to their normal position. We first ask, how would members observe an emerging consensus of mandate? And then we model the duration of the change in behavior in an event‐history framework. That permits a depiction of important movements of the median member and, from this, inferences about policy impact.     

European Union Decision Making: the Role of Sub-national Authorities

This article assesses how and to what extent sub-national authorities (SNAs) are represented in EU decision making. In particular, we compare the European goals and strategies of British sub-national authorities with those of their counterparts in Germany. Our central argument is that SNAs starting from very different positions face many of the same challenges and problems, even if their domestic constitutional positions remain the most important determinant of their influence at the EU level. Influence in EU decision making derives largely from effective coalition building, both with other like-minded actors but also, inevitably in the case of sub-national authorities, with central governments. Our case study highlights the enormous diversity of relationships between central governments and 'their' SNAs across the Union. It thus encourages scepticism about the feasibility of a 'Europe of the Regions'.