Microchip-based cell lysis and DNA extraction from sperm cells for application to forensic analysis

The current backlog of casework is among the most significant challenges facing crime laboratories at this time. While the development of next-generation microchip-based technology for expedited forensic casework analysis offers one solution to this problem, this will require the adaptation of manual, large-volume, benchtop chemistry to small volume microfluidic devices. Analysis of evidentiary materials from rape kits where semen or sperm cells are commonly found represents a unique set of challenges for on-chip cell lysis and DNA extraction that must be addressed for successful application. The work presented here details the development of a microdevice capable of DNA extraction directly from sperm cells for application to the analysis of sexual assault evidence. A variety of chemical lysing agents are assessed for inclusion in the extraction protocol and a method for DNA purification from sperm cells is described. Suitability of the extracted DNA for short tandem repeat (STR) analysis is assessed and genetic profiles shown. Finally, on-chip cell lysis methods are evaluated, with results from fluorescence visualization of cell rupture and DNA extraction from an integrated cell lysis and purification with subsequent STR amplification presented. A method for on-chip cell lysis and DNA purification is described, with considerations toward inclusion in an integrated microdevice capable of both differential cell sorting and DNA extraction. The results of this work demonstrate the feasibility of incorporating microchip-based cell lysis and DNA extraction into forensic casework analysis.     

Probability of exclusion in paternity testing: time to reassess

The average exclusion probability is a measure of efficiency in paternity testing; it refers to the a priori ability of a battery of tests to detect paternity inconsistencies. This parameter measures the capacity of the system to detect a false accusation of paternity. Traditionally, this average exclusion probability has been estimated as the probability of excluding a man who is not the father by an inconsistency in at least one of the studied loci. We suggest that this criterion should be corrected, as currently the presumed father is excluded when at least three genetic inconsistencies are found with the child being tested, not just one. This change of criterion has occurred because of the use of microsatellite loci, whose mutation rates are much greater than those of the coding genes used previously in paternity studies. We propose the use of the average probability of exclusion for at least three loci (not only one), as an honest measure of the combined probability of exclusion of several loci, and we propose an algebraic expression to calculate it.     

Dietary health does affect histological age assessment: an evaluation of the Stout and Paine (1992) age estimation equation using secondary osteons from the rib

An age at death estimation equation that uses rib histological variables presented by Stout and Paine was used to evaluate a skeletal population of individuals with a known age at death and cause of death from either malnutrition or the niacin deficiency disease pellagra. The sample was comprised of 26 autopsied black South Africans. Histological analysis of mounted thin sections involved the microscopic measurement of cortical area and a count of the number of intact and fragmentary secondary osteons for the entire cross-section of the rib. Rib osteon population density values were then calculated for each case. It was found that this equation under-aged individuals on average by 29.2 years. Overall, secondary osteon size and Haversian canals tended to be larger than expected, while cortical bone area was less when compared with a control population. The implications of these findings are critical given that many of the skeletal remains examined by forensic anthropologists come from marginalized backgrounds, including malnutrition. This research suggests that measurements based on healthy cases may not be useful in an analysis of individuals with poor diet and health. It is argued that new standards for histological age assessment methods need to be created that account for variation in the health status of individuals examined by forensic anthropologists.     

Reduction of postmortem angiography-induced tissue edema by using polyethylene glycol as a contrast agent dissolver

Postmortem investigation is increasingly supported by computed tomography (CT) and magnetic resonance imaging, in which postmortem minimal invasive angiography has become important. The newly introduced approach using an aqueous contrast agent solution provided excellent vessel visualization but was suspected to possibly cause tissue edema artifacts in histological investigations. The aim of this study was to investigate on a porcine heart model whether it is possible to influence the contrast agent distribution within the soft tissue by changing its viscosity by dissolving the contrast agent in polyethylene glycol (PEG) as a matrix medium. High-resolution CT scans after injection showed that viscosities above c. 15 mPa s (65% PEG) prevented a contrast agent distribution within the capillary bed of the left ventricular myocardium. Thereby, the precondition of edema artifacts could be reduced. Its minimal invasive application on human corpses needs to be further adapted as the flow resistance is expected to differ between different tissues.     

Forensic medical differential diagnosis of craniocerebral trauma in children

It is emphasized that history, complaints, a comprehensive neurological examination, craniography are not often sufficient for differentiation between brain concussion and mild brain contusion in children because of specific characteristics of craniocerebral trauma (CCT) in such patients. To make an adequate forensic medical diagnosis of CCT in children, it is necessary to take into consideration anatomophysiological peculiarities of a child, biomechanical conditions of the brain injury, to apply modern methods of neurovisualization (ultrasonography, computed and MR imaging), to follow up brain function with quantitative electroencephalography. Improvement of differential forensic-medical assessment of CCT severity in childhood should be made according to the principles of evidence-based medicine.     

Strategy of multiplex analysis of STR-loci polymorphism of Y-chromosome on the basis of "minimal haplotype"

A molecular-genetic analysis of Y chromosome is a convenient tool of paternal affinity determination. This method is now widely introduced in expert practice. Previous experience in typing of Y chromosome is outlined. Strategy of development and experience in operating a multiplex system for a simultaneous analysis of seven STR loci of Y chromosome is discussed.     

Strategic Use of Evidence During Police Interviews: When Training to Detect Deception Works

Research on deception detection in legal contexts has neglected the question of how the use of evidence can affect deception detection accuracy. In this study, police trainees (N=82) either were or were not trained in strategically using the evidence when interviewing lying or truth telling mock suspects (N=82). The trainees’ strategies as well as liars’ and truth tellers’ counter-strategies were analyzed. Trained interviewers applied different strategies than did untrained. As a consequence of this, liars interviewed by trained interviewers were more inconsistent with the evidence compared to liars interviewed by untrained interviewers. Trained interviewers created and utilized the statement-evidence consistency cue, and obtained a considerably higher deception detection accuracy rate (85.4%) than untrained interviewers (56.1%).     

Pink teeth in a series of bodies recovered from a single shipwreck

Pink teeth have most often been observed in victims of drowning but have also been reported in subjects who died suddenly and unnaturally. There is general agreement that there is no obvious connection between the occurrence of pink teeth and the cause of death, but the condition of the surroundings (especially humidity) must certainly play an important role in the development of the pink-tooth phenomenon. The frequency and distribution of postmortem pink coloration of the teeth have been studied among a representative sample of 52 cadavers. All the bodies were victims of a single shipwreck that occurred on March 13, 1997, in the middle of the Otranto Canal (Mediterranean Sea). The bodies were recovered from the seawater after approximately 7 months. A distinct pink coloration of the teeth was found in only 18 cadavers (13 females and 5 males) of ages ranging between 13 and 60 years. The phenomenon was more pronounced in younger individuals due to age-related changes of the root canal, less penetrable by the pigment responsible for the postmortem pink staining. By histochemical methods and autofluorescence, hemoglobin and its derivatives have been identified as the most likely pigments responsible for this postmortem process that can be considered analogous to postmortem lividity. These data are consistent with previous reports on pink teeth, indicating that the diffusion of the blood in the pulp into the dentinal tubules causes the red discoloration of the teeth. Based on the results, the pigmentation is more prominent on the teeth with single roots rather than in the posterior teeth with multiple roots.