Effects of different storage and measuring methods on larval length values for the blow flies (Diptera: Calliphoridae) Lucilia sericata and Calliphora vicina

In forensic entomology, the methods of sampling, killing, and storing entomological samples can affect larval age estimation, and, hence, the estimation of the minimum post-mortem interval. In the existing manuals, there is a certain amount of heterogeneity regarding methods and the recommendations for best practice in forensic entomology are insufficiently validated. This study evaluated three different length-measurement methods for larval stages and examined the influence of different killing and storing methods on the larval length of two forensically important blow flies, Lucilia sericata and Calliphora vicina. The three different measuring methods were a) a ruler with a 0.1 mm scale, b) a geometrical micrometer, and c) a computer-aided stereomicroscope. They were used to measure the length of L1 –L 3 C. vicina larvae and detect no significant differences. This supports the view that a simple tool like a geometrical micrometer can produce reliable results in forensic entomology. Newly hatched larvae of L. sericata and C. vicina were killed with hot water (HW) and divided into two equal subsamples. Lengths of all larvae were measured immediately after killing, then every 24 h until day 4, and once more after 7 days of storage in ≥70%-ethanol. L. sericata larvae only showed significant changes in length in the HW group stored at room temperature. After 4 and 7 days of storage, these 24-h- and 72-h-old larvae showed a significant decrease in length compared with those in a fridge at 6 °C. This decrease can, however, be considered a negligible natural variation without forensically relevant consequences for larval age estimation of L. sericata samples. For C. vicina, an increase in length was observed over time. This was significant only for younger larvae (24-48 h old) stored in 70%-ethanol. This variance in length can lead to a wrong estimation of age; however, only for larvae stored in 70%-ethanol, not for those stored in 96%-ethanol. Novelty statement: We examined the influence of different killing and storing methods on two forensically important blow flies, Lucilia sericata and Calliphora vicina. For the latter species we additionally were evaluating three different length measurement methods. The results of both experiments suggest that it is possible to kill and store fly larvae directly in (not hot) ≥70%-ethanol. This simplifies the sampling and storing of fly evidence at the crime scene. We also compared the influence of three different measuring methods for estimating the length of L1–L3 C. vicina larvae by using a) a ruler with a 0,1 mm scaling, b) a geometrical micrometer and c) a computer-aided stereomicroscope. No significant differences were detected, supporting the view, that a simple tool like a geometrical micrometer can produce reliable results. This study helps to simplify the sampling and evaluation of entomological evidence and to backup or questioning existing guidelines and best practice recommendations

Effects of different storage and measuring methods on larval length values for the blow flies (Diptera: calliphoridae) Lucilia sericata and Calliphora vicina

In forensic entomology, the methods of sampling, killing, and storing entomological samples can affect larval age estimation, and, hence, the estimation of the minimum post-mortem interval. In the existing manuals, there is a certain amount of heterogeneity regarding methods and the recommendations for best practice in forensic ento- mology are insufficiently validated. This study evaluated three different length-measurement methods for larval stages and examined the influence of different killing and storing methods on the larval length of two forensically important blow flies, Lucilia sericata and Calliphora vicina. The three different measuring methods were a) a ruler with a 0.1 mm scale, b) a geometrical micrometer, and c) a computer-aided stereomicroscope. They were used to measure the length of L1–L3 C. vicina larvae and detect no significant differences. This supports the view that a simple tool like a geometrical micrometer can produce reli- able results in forensic entomology. Newly hatched larvae of L. sericata and C. vicina were killed with hot water (HW) and divided into two equal sub- samples. Lengths of all larvae were measured immediately after killing, then every 24 h until day 4, and once more after 7 days of storage in ≥70%-ethanol. L. sericata larvae only showed significant changes in length in the HW group stored at room temperature. After 4 and 7 days of storage, these 24-h- and 72-h-old larvae showed a significant decrease in length compared with those in a fridge at 6 °C. This decrease can, however, be considered a negligible natural variation without foren- sically relevant consequences for larval age estimation of L. sericata samples. For C. vicina, an increase in length was observed over time. This was significant only for younger larvae (24-48 h old) stored in 70%-ethanol. This variance in length can lead to a wrong estimation of age; however, only for larvae stored in 70%-ethanol, not for those stored in 96%-ethanol. Novelty statement: We examined the influence of different killing and storing methods on two forensically impor- tant blow flies, Lucilia sericata and Calliphora vicina. For the latter species we additionally were evaluating three different length measurement methods. The results of both experiments suggest that it is possible to kill and store fly larvae directly in (not hot) ≥70%-ethanol. This simplifies the sampling and storing of fly evidence at the crime scene. We also compared the influence of three different measuring methods for estimating the length of L1–L3 C. vicina larvae by using a) a ruler with a 0,1 mm scaling, b) a geometrical micrometer and c) a comput- er-aided stereomicroscope. No significant differences were detected, supporting the view, that a simple tool like a geometrical micrometer can produce reliable results. This study helps to simplify the sampling and evaluation of entomological evidence and to backup or questioning existing guidelines and best practice recommendations

Osteological sex determination using hard palate measurements

Hintergrund: Nach Auffindung von skelettierten menschlichen Überresten ist die Bestimmung des Geschlechts ein wesentliches Element des sog. biologischen Profils. Neben den molekularbiologischen Methoden zur Geschlechtsbestimmung basieren die am häufigsten verwendeten Techniken auf den morphologischen Eigenschaften des Beckens und des Schädels. Da man im forensischen Zusammenhang häufig auf unvollständige Skelette oder fragmentierte Becken- und Schädelknochen trifft, ist es sinnvoll, nach alternativen Merkmalen und Maßen zu suchen, die eine ausreichend gute Korrelation zum Geschlecht aufweisen. Ziel der Arbeit: Anhand postmortaler CT-Daten soll der menschliche Gaumen vermessen und überprüft werden, ob ein Zusammenhang zwischen den Messergebnissen und dem Geschlecht besteht. Material und Methoden: An 58 virtuellen 3D-rekonstruierten Schädeln (40 männlich, Altersmittelwert 41,7 Jahre, und 18 weiblich, Altersmittelwert 46,6 Jahre) wurden die Gaumenmaße (Gaumenhöhe, vordere Gaumenhöhe, Gaumenbreite und vordere Gaumenbreite) digital vermessen. Aus Gaumenhöhe und Gaumenbreite wurde der Gaumenhöhenindex zur Charakterisierung der Gaumenwölbung berechnet. Ergebnisse: Für die vordere Gaumenhöhe, die Gaumenbreite und die vordere Gaumenbreite konnte mithilfe der Korrelationsanalyse nach Pearson statistisch kein signifikanter Zusammenhang mit dem Geschlecht festgestellt werden. Dagegen war für die Gaumenhöhe eine positive Korrelation nach Pearson auf einem Signifikanzniveau von 99 % (2-seitig) nachweisbar. Allerdings ist aufgrund der zu geringen Trennschärfe eine praktische Anwendung zur Geschlechtsdiskrimination nicht ableitbar. Schlussfolgerung: In Bezug auf die Gaumenwölbung konnte bei 20 der 40 männlichen Individuen und bei 6 der 18 weiblichen Individuen der Gaumenhöhenindex berechnet werden. Die meisten männlichen Individuen waren demnach mittelhochgaumig, die meisten weiblichen Individuen niedergaumig und keines hochgaumig. Mittelhoch- und insbesondere Hochgaumigkeit sprechen insofern am ehesten für ein männliches Individuum. Die Gaumenwölbung könnte als ergänzender Feldtest sinnvoll sein. Allerdings wäre eine Überprüfung aller Paramater an einer deutlich größeren Stichprobe zu empfehlen. Hierbei sollte außerdem auf ein ausgeglicheneres Geschlechterverhältnis der Studienpopulation geachtet werden

A molecular, morphological, and physiological comparison of English and German populations of Calliphora vicina (Diptera: Calliphoridae).

The bluebottle blow fly Calliphora vicina is a common species distributed throughout Europe that can play an important role as forensic evidence in crime investigations. Developmental rates of C. vicina from distinct populations from Germany and England were compared under different temperature regimes to explore the use of growth data from different geographical regions for local case work. Wing morphometrics and molecular analysis between these populations were also studied as indicators for biological differences. One colony each of German and English C. vicina were cultured at the Institute of Legal Medicine in Frankfurt, Germany. Three different temperature regimes were applied, two constant (16°C & 25°C) and one variable (17-26°C, room temperature = RT). At seven time points (600, 850, 1200, 1450, 1800, 2050, and 2400 accumulated degree hours), larval lengths were measured; additionally, the durations of the post feeding stage and intrapuparial metamorphosis were recorded. For the morphometric and molecular study, 184 females and 133 males from each C. vicina population (Germany n = 3, England n = 4) were sampled. Right wings were measured based on 19 landmarks and analyzed using canonical variates analysis and discriminant function analysis. DNA was isolated from three legs per specimen (n = 61) using 5% chelex. A 784 bp long fragment of the mitochondrial cytochrome b gene was sequenced; sequences were aligned and phylogenetically analyzed. Similar larval growth rates of C. vicina were found from different geographic populations at different temperatures during the major part of development. Nevertheless, because minor differences were found a wider range of temperatures and sampling more time points should be analyzed to obtain more information relevant for forensic case work. Wing shape variation showed a difference between the German and English populations (P<0.0001). However, separation between the seven German and English populations at the smaller geographic scale remained ambiguous. Molecular phylogenetic analysis by maximum likelihood method could not unambiguously separate the different geographic populations at a national (Germany vs England) or local level.© 2018 Limsopatham et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of this article

Skin tension and cleavage lines (Langer' s lines) causing distortion of ante- and postmortem wound morphology

The assessment of individual wounds at autopsy may be complicated by the superimposition of a number of injuries or damage to tissues that occurred after death, either of which has the potential to distort the morphology of the initial injury. Additional factors that may change the shape of wounds are (1) the relationship of the wound to the so-called skin cleavage lines (Langer’s lines) and (2) tension placed on the skin. Three autopsy cases are reported to demonstrate once more how wound morphology may be altered by such factors. In case 1, rectangular stab wounds to the base of the neck in a 53-year-old man, which suggested that a square or rectangular tool may have caused the injuries, were altered to more typical knife stab wounds once skin tension had been released at autopsy. The uppermost wounds, however, continued to gape due to the effects of skin cleavage lines. In case 2, slit-like wounds resembling stab wounds in the neck of a 54-year-old woman found in a river were shown to be circular once skin tension had been released. In case 3, the effects of either cleavage lines or skin tension could be demonstrated on excised wounds from a 43-year-old man whose body had also been found in a river; tensile forces easily changed circular into slit-like wounds. Tension and/or skin cleavage lines may transform round skin defects into slit-like wounds resembling knife stab wounds, round out genuine stab wounds and artefactually lengthen stab wounds. These factors must be taken into consideration carefully when wounds are assessed at the death scene prior to autopsy.Roger W. Byard, Axel Gehl, Michael Tsoko

Does cone beam CT actually ameliorate stab wound analysis in bone?

This study aims at verifying the potential of a recent radiological technology, cone beam CT (CBCT), for the reproduction of digital 3D models which may allow the user to verify the inner morphology of sharp force wounds within the bone tissue. Several sharp force wounds were produced by both single and double cutting edge weapons on cancellous and cortical bone, and then acquired by cone beam CT scan. The lesions were analysed by different software (a DICOM file viewer and reverse engineering software). Results verified the limited performances of such technology for lesions made on cortical bone, whereas on cancellous bone reliable models were obtained, and the precise morphology within the bone tissues was visible. On the basis of such results, a method for differential diagnosis between cutmarks by sharp tools with a single and two cutting edges can be proposed. On the other hand, the metrical computerised analysis of lesions highlights a clear increase of error range for measurements under 3 mm. Metric data taken by different operators shows a strong dispersion (% relative standard deviation). This pilot study shows that the use of CBCT technology can improve the investigation of morphological stab wounds on cancellous bone. Conversely metric analysis of the lesions as well as morphological analysis of wound dimension under 3 mm do not seem to be reliable

Postmortem computed tomography age assessment of juvenile dentition:comparison against traditional OPT assessment

Age estimation is one of the primary demographic features used in the identification of juvenile remains. Determining the accuracy and repeatability of age estimations based on postmortem computed tomography (PMCT) data compared with those using conventional orthopantomography (OPT) images is important to validate the use of PMCT as a single imaging technique in forensic and disaster victim identification (DVI). In this study, 19 juvenile mandibles and maxilla of known age underwent both OPT and PMCT. Three raters then estimated dental age using the resulting images and 3D reconstructions. This assessment showed excellent agreement between the age estimations using the two techniques for all three observers. PMCT also offers a greater range of measurements for both the dentition and the whole human skeleton using a single image acquisition and therefore has the potential to improve both the speed and accuracy of age estimation