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 application of signal detection theory to decision-making in forensic science

Signal Detection Theory (SDT) has come to be used in a wide variety of fields where noise and imperfect signals present challenges to the task of separating hits and correct rejections from misses and false alarms. The application of SDT helps illuminate and improve the quality of decision-making in those fields in a number of ways. The present article is designed to make SDT more accessible to forensic scientists by: (a) explaining what SDT is and how it works, (b) explicating the potential usefulness of SDT to forensic science, (c) illustrating SDT analysis using forensic science data, and (d) suggesting ways to gain the benefits of SDT analyses in the course of carrying out existing programs of quality assessment and other research on forensic science examinations.     

‘new wars’ and gendered economies

Feminist Review - This paper draws on the ‘new wars’ literature and global political economy research to explore how feminists and other critical analysts might investigate linkages...     

Duverger's Laws: Between social and institutional determinism

Abstract. The purpose of this article is to relocate Duverger's Laws within the debate about the effects of electoral systems on the number of parties. Although Duverger's theory has always been seen as the best example of a purely institutionalist approach to the issue, it is possible to argue that this is only true if one overemphasises the meaning of the laws without considering Duverger's justification and explanations for them. However, if one takes into consideration not only the laws, but also Duverger's theories about the effects of electoral systems on the number of parties as a whole, one can argue that his theses do not have a purely institutionalist character and can therefore coexist with theories that try to take into account variables other than electoral rules.