Interdisciplinary cooperation of forensic sciences--results of a simulation exercise

In a workshop held on the occasion of the foundation of the INFW, the Interdisciplinary Network of Forensic Sciences (www.infw.org), 14 scientists from 10 fields of expertise were allotted to 3 teams. Each team had to independently solve the same fictitious forensic case. In this, several corpses or skeletons in varying degrees of decomposition were found in the remains of an old bunker during a large building project. After a set time limit of 45 minutes, the approaches to the task were noted on individual flipcharts by each team. A comparison of the solutions suggested by the three very heterogeneously composed teams revealed a high degree of similarity. However, particularly the "exotic" disciplines developed surprising approaches. The experiment was an interesting and instructive experience for all participants and underscores the necessity of interdisciplinary cooperation in solving complex forensic questions.     

Incestuous paternity detected by STR-typing of chorionic villi isolated from archival formalin-fixed paraffin-embedded abortion material using laser microdissection

Microscopic examination of a blood clot expelled by a physically and mentally disabled woman taken to the emergency room because of genital bleeding revealed the presence of chorionic villi encircled by decidua, hemorrhage, and necrosis. In order to identify the father of the product of conception, sections of formalin-fixed, paraffin-embedded abortion material were subjected to laser microdissection: DNA extraction from chorionic villi selectively isolated from the surrounding tissues allowed successful STR-typing of fetal cells, which was otherwise prevented by excess maternal DNA. The large number of homozygous genotypes in the fetal profile suggested incestuous paternity. Analysis of reference DNA samples from male relatives excluded the woman's father, paternal grandfather, and maternal grandfather, whereas the obligate paternal alleles of the fetus were constantly present in the genotypes of the woman's brother, clearly demonstrating brother-sister incest (probability of paternity > 99.99999%).     

Forensic analysis of bicomponent fibers using infrared chemical imaging

The application of infrared chemical imaging to the analysis of bicomponent fibers was evaluated. Eleven nominally bicomponent fibers were examined either side-on or in cross-section. In six of the 11 samples, infrared chemical imaging was able to spatially resolve two spectroscopically distinct regions when the fibers were examined side-on. As well as yielding characteristic infrared spectra of each component, the technique also provided images that clearly illustrated the side-by-side configuration of these components in the fiber. In one case it was possible to prepare and image a cross-section of the fiber, but in general the preparation of fiber cross-sections proved very difficult. In five of the 11 samples, the infrared spectra could be used to identify the overall chemical composition of the fibers, according to a published classification scheme, but the fiber components could not be spatially resolved. Difficulties that are inherent to conventional "single-point" infrared spectroscopy, such as interference fringing and sloping baselines, particularly when analyzing acrylic type fibers, were also encountered in the infrared chemical image analysis of bicomponent fibers. A number of infrared sampling techniques were investigated to overcome these problems, and recommendations for the best sampling technique are given. Chemical imaging results were compared with those obtained using conventional fiber microscopy techniques.     

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.     

Alpha-amylase kinetic test in bodily single and mixed stains

Recently, in Italy, a murder and a putative sexual violence was accomplished on a child. A bodily fluids mixture on the child's underwear between the victim (female) and the suspect (male) was ascertained by short tandem repeat (STR) DNA typing and, due to the absence of seminal fluid, saliva from the suspect and urine from the child was hypothesized. In order to investigate the possibility of specifically and rapidly detecting saliva stains both alone and mixed with other bodily fluids, we used a quantitative spectrophotometric technique, named Amylase test, for the detection of alpha-amylases. We determined alpha-amylase activity and reaction kinetic curves in several samples collected from the child's underwear. In order to confirm our intuition, we first tested saliva, perspiration, and urine, singularly and in mixtures; second, several forensic stains including saliva, perspiration, urine stains, saliva/perspiration, and saliva/urine mixture stains were tested. Evaluating alpha-amylase activity values and time-course curves' behavior of alpha-amylase reactions we were able to recognize successfully, in all cases, the presence of saliva and to distinguish it specifically from other bodily fluids containing alpha-amylase. A further confirmation of our result was provided by STR DNA typing on several areas of the underwear: a clear correlation between alpha-amylases activity and male DNA was detected on all the samples evaluated.     

Violent Sex Offenses: How are They Best Measured from Official Records?

In the United States, sexually violent predator (SVP) commitment statutes generally require assessment of an offender's risk of subsequent sexual violence. Current actuarial methods for predicting sexual reoffending were actually designed to predict something else—charges or convictions for offenses deemed sexual based on information obtained from police “rapsheets” alone. This study examined the referral and past offenses of 177 sex offenders. Results showed that police rapsheets (and data based on them) underestimated the number and severity of sexually motivated violent offenses for which sex offenders were actually apprehended. Rapsheet violent offenses seemed a more accurate index of the conduct addressed by SVP legislation than were rapsheet sex offenses. We suggest that, when evaluating sex offenders for SVP status, actuarial instruments designed to predict violent recidivism (as measured by rapsheet violent reoffenses) might be preferable to those designed to predict sexual recidivism (as measured by rapsheet sexual reoffenses).

Further evidence of the validity of the Suicide Risk Assessment Scale for prisoners

The Suicide Risk Assessment Scale (SRAS; nine items) is useful in correctional settings but needed further validation. First, 44 inmates originally screened as suicidal with the SRAS were evaluated by institutional psychologists according to five criteria: suicidal urgency, risk, appropriateness of referral, need for short- or long-term watch. On the whole, the SRAS was judged to be as effective as a more elaborate test. Second, 242 suicidal and non-suicidal inmates were tested with the SRAS. Their results correlated better with suicidal risk (.71) than with urgency (.50). Receiver operating characteristic (ROC) analysis even showed that the SRAS performed better than a more elaborate test in predicting risk.