Mutation rates at 14 STR loci in the population from Pernambuco, Northeast Brazil

Definition about mutation rates of short tandem repeats (STRs) loci used in forensic analysis are useful for the correct interpretation of resulting genetic profiles and the definition of criterions for exclusion in paternity testing. Germline mutation of 14 STR loci was studied for 54,105 parent–child allelic transfers from 2575 paternity testing cases carried out during 2000–2007 from the Pernambuco State, Northeast Brazil. The parenthood in each of these cases was highly validated (probability > 99.99%). We identified 43 mutations at 12 loci. Locus-specific mutation rate estimates varied between 2 × 10⁻⁴ and 2 × 10⁻³, and the overall mutation rate estimate was 8 × 10⁻⁴. Mutation events in the male germline were more frequent than in the female germline. The majority of the mutations could be explained by losses or gains of one repeat unit and there was no evidence for selection between insertion or deletion changes. Our data were compared with those of Portuguese and North-American populations for CSF1PO, D18S51, D21S11, D7S820, TH01, TPOX and demonstrated, despite the great difference in the size of the sample, that mutation rates of STR loci in a mixed population do not differ from that encountered in different populations.     

Homicidal hanging

We report a case of homicide by hanging of a 29-year-old woman that was committed by her husband, who nearly escaped from justice. We offer some reflections on the rarity of this method of mechanical asphyxia in cases of homicide, and on the difficulties in the diagnosis of the medico-legal etiology of these situations. We also offer a short review of similar cases in the medico-legal literature.     

Demystifying "oxi" cocaine: Chemical profiling analysis of a "new Brazilian drug" from Acre State

Recent information from various sources suggests that a new illicit drug, called "oxi", is being spread across Brazil. It would be used in the smoked form and it would look like to crack cocaine: usually small yellowish or light brown stones. As fully released in the media, "oxi" would differ from crack cocaine in the sense that crack would contain carbonate or bicarbonate salts whereas "oxi" would include the addition of calcium oxide and kerosene (or gasoline). In this context, this work presents a chemical profiling comparative study between "oxi" street samples seized by the Civil Police of the State of Acre (CP/AC) and samples associated with both international and interstate drug trafficking seized by the Brazilian Federal Police in Acre (FP/AC). The outcome of this work assisted Brazilian authorities to stop inaccurate and alarmist releases on this issue. It may be of good use by the forensic community in order to better understand matters in their efforts to guide local law enforcement agencies in case such claims reach the international illicit market.     

Analytical method for the determination of strychnine in tissues by gas chromatography/mass spectrometry: two case reports

This paper describes an analytical method for strychnine determination in biological samples by gas chromatography/mass spectrometry and their application in the investigation of two cases involving strychnine ingestion: A fatal case and a clinical one. The strychnine is isolated from biological samples using a liquid-liquid extraction procedure. The clean-up procedure is performed using an acid solution. Papaverine is used as internal standard in the quantification of strychnine. In the analysed specimens, the limits of quantification were 0.1 microg/ml or 0.1 microg/g. The recovery rate ranged from 75.0% to 98.7% and the coefficients of variation ranged from 4.8% to 10.5%.     

Analytical approach to determine ticlopidine in post-mortem blood

A new and sensitive method to determine ticlopidine in whole human blood using proadifen as the internal standard (IS) is described. The analyte and IS were extracted by solid-phase extraction using Oasis HLB cartridges, and the extracts were analyzed by gas chromatography-electron impact ionisation-mass spectrometry (GC/EI-MS). Calibration curves were established daily in spiked blood samples using a non-linear calibration model, between 0.01 and 4.5 microg/mL. The correlation coefficients were higher than 0.995. Precision and accuracy fulfilled the internationally accepted criteria (coefficients of variation were less than 9%, and the measured concentrations were within +/-7% of the true value). Limits of detection and quantitation were respectively, 3 and 10 ng/mL. No interfering substances were detected by analysis of 10 blank blood samples of different origin. Mean recovery, calculated at three concentration levels, was 71%. Because of its simplicity and speed, the proposed method can be applied in the determination of this inhibitor of platelet aggregation in whole blood samples, and is suitable for application in toxicology routine analysis.     

Population study of HUMTH01, HUMVWA31/A, HUMF13A1, and HUMFES/FPS systems in Azores

The tetrameric short tandem repeat polymorphisms HUMTH01, HUMVWA31/A, HUMF13A1, and HUMFES/FPS were studied in blood stains obtained from a population of unrelated individuals from the Azores Archipelago (Portugal). Gene frequencies were determined and no deviation from the Hardy-Weinberg equilibrium was found. However, the allelic independence test between loci showed linkage disequilibrium between HUMVWA31/A and HUMFES/FPS. A combined discrimination power and chance of exclusion of, respectively, 0.9999 and 0.9534, reveal the high forensic interest of the four systems. No differences with other caucasoid populations were found, but comparison with some asiatic, eskimo, and amerindian populations showed significant statistical differences.     

The effectiveness of judicial instructions on eyewitness evidence in sensitizing jurors to suggestive identification procedures captured on video

Journal of Experimental Criminology - One of the legal safeguards designed to educate jurors about eyewitness evidence is judicial instructions. However, their effectiveness in sensitizing jurors...