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Automatic speaker recognition (ASR) is a method used in forensic speaker comparison (FSC) casework. It needs collections of audio data that are representative of the case audio in order to perform reference normalization and to train a score-to-LR function. Audio from a certain minimum number of speakers is needed for each of those purposes to obtain relatively stable performance of ASR. Although it is not possible to set a hard cut-off, for the purpose of this work this number was chosen to be 30 for each, and 60 for both. Lack of representative data from that many speakers and uncertainty about what exactly constitutes representative data are major reasons for not employing ASR in FSC. An experiment was carried out in which a situation was simulated where a practitioner has only 30 speakers available. Several data strategies are tried out to handle the lack of data: leaving out reference normalization, splitting the 30 speakers into two groups of 15 (ignoring the minimum of 30) and a leave 1 or 2 out strategy where all 30 speakers are used for both reference normalization and calibration. They are compared to the baseline situation where the practitioner does have the required 60 speakers. The leave 1 or 2 out strategy with 30 speakers performs on par with baseline, and extension of that strategy to the full 60 speakers even outperforms baseline. This shows that a strategy that halves the data need is viable, lessening the data requirements for ASR in FSC and making the use of ASR possible in more cases. •Several data strategies for forensic speaker comparison casework are compared.•When having too few data, one strategy is found that still performs on par with having enough data.•Data need for casework is cut in half.•When there is enough data, a data strategy is found that outperforms a baseline strategy.

Some research has identified the prevalence and motivation of using condoms by assailants during sexual assault cases proving the necessity of analyzing condom trace evidence. The majority of the papers published have discussed forensic analysis of lubricants from condoms retrieved at sexual assault scenes but those discussing the identification of semen from condoms are rare. Therefore, the present study aims to provide insight into the detectability of the semen that remained in a condom, to examine the effect of exposure time, environmental conditions, and condom type, and ultimately to determine the capability of the AP test and Microscopic examination for identification of this sample type. In the study, samples were collected from three male donors after being instructed on the proper way of collecting the semen sample. The received samples from the donors were checked first by microscopic examination to observe the sperm to confirm that the sample being handled was semen. After confirmation, samples were transferred to 4 prepared condoms (brands: dkt xxx and Manforce) and kept in conditions i.e. two condoms in a refrigerator maintained from 2 to 10°C and other ones at ambient temperature (weather status: summer season of average 39°C). The samples were analyzed into two batches, the first analysis batch was conducted after the samples were exposed to the conditions within 11–60 days. After analysis from the first batch, the samples were continuously kept in the same condition for the consecutive second batch conducted when the samples reached 40–90 days. This study has determined that semen remaining in a condom can be detected and each test studied is appropriate according to the exposure stage, i.e., time and conditions of exposure. It has been found that nonmotile spermatozoa can be observed when semen remains in the condom for a few days. However, if the sample reaches approximately 25 days at room temperature above 25°C or 54 days below 10°C, the semen may dry out limiting the effectiveness of microscopic examination. Despite this, even semen that remained in a condom for up to 90 days can be identified by Acid Phosphatase. Results on condom type used reveal that condom constituents can crossreact with semen but none of them can limit the semen identification with Acid Phosphatase. •When semen stays for a few days in the condom there could be the chance to observe nonmotile spermatozoa.•Conditions to which the condom is exposed were found to have effects on one test used in semen identification.•Condom constituents can crossreact with semen but none of them can limit the semen identification.•All the samples processed for AP testing yielded positive results.

Forensic anthropologists working with cases that vary in stages of decomposition are often required to process and macerate remains to complete a forensic analysis. Maceration techniques vary between laboratories, and procedures to facilitate maceration of fetal and perinatal remains are lacking in the literature. This descriptive case study evaluates the use of several maceration techniques for fetal and perinatal remains (n = 2), including cold-water bacterial maceration, hot-water enzymatic maceration, dehydration, and incubation. Dehydration is a new maceration technique previously unpublished. For each technique, the authors assessed ease of maceration, effect on bone quality, and utility for forensic casework and/or donated remains and found all techniques are easy to implement and do not greatly diminish bone quality. Previous research recommends hot-water enzymatic maceration for forensic casework, as it will not degrade DNA and can efficiently remove soft tissues. This case study corroborates this recommendation but finds that incubation may be preferred for fetal remains, as it is quicker and less labor intensive. However, cold-water maceration and dehydration are recommended for donated fetal remains. Cold-water maceration is low maintenance, minimally malodorous, and preferable for disarticulated teaching materials, since this technique avoids any heat-induced warping of fetal bones. Dehydration retains cartilaginous structures and allows for the preservation of articulated elements for comparative specimens in donated collections. By demonstrating several techniques for fetal and perinatal maceration, this case study serves as a starting point toward the creation of general guidelines for forensic anthropology practitioners.

Capillary electrophoresis (CE) is widely used in forensic genetics to study short tandem repeats (STRs). Recently, next-generation sequencing (NGS) platforms have facilitated the development of new strategies for forensic DNA typing. Several studies have shown that NGS successfully analyzes challenging samples. However, because NGS is complicated and time-consuming, it remains unclear whether NGS platforms offer significant advantages over CE for all forensic cases. Here, the MiSeq FGx system was used to test some cases that had previously been analyzed using CE. These cases included paternity test cases in which some samples exhibited locus inconsistencies; samples with off-ladder (OL) alleles; samples with triallelic patterns; and samples with amelogenin test abnormalities. The results generated by MiSeq FGx were compared to those previously generated by CE. The MiSeq FGx and CE results were consistent with the exception of three samples, where inconsistencies were observed at the Penta D locus. For all three incongruent samples, the MiSeq FGx results were correct. Sequence analysis indicated that, in two cases, mismatches were due to undetected alleles rather than mutations. In two additional cases, mutation sources were identified, and in a fifth case, mutation step size was reconsidered. MiSeq FGx was used to identify OL alleles and samples with amelogenin test abnormalities. For cases where verification was required via CE analysis, the simultaneous NGS amplification of several types of multiple genetic markers improved testing efficiency. In addition, we identified additional sequence variants at autosomal, Y chromosomal, and X chromosomal STR loci in the Han Chinese population from northern China. Our results will be useful for future forensic analyses of STR genotypes in Chinese populations. It is likely that NGS would be more widely used in forensic genetics if costs and procedure complexity were reduced.

Post-mortem chemical excitability of the iris is one of the non-temperature-based methods in forensic diagnosis of the time since death. Although several authors reported on their findings, using different measurement methods, currently used time limits are based on a single dissertation which has recently been doubted to be applicable for forensic purpose. We investigated changes in pupil-iris ratio after application of acetylcholine (n = 79) or tropicamide (n = 58) and in controls at upper and lower time limits that are suggested in the current literature, using a digital photography-based measurement method with excellent reliability. We observed “positive,” “negative,” and “paradox” reactions in both intervention and control conditions at all investigated post-mortem time points, suggesting spontaneous changes in pupil size to be causative for the finding. According to our observations, post-mortem chemical excitability of the iris should not be used in forensic death time estimation, as results may cause false conclusions regarding the correct time point of death and might therefore be strongly misleading.

Re-establishment of rigor mortis following mechanical loosening is used as part of the complex method for the forensic estimation of the time since death in human bodies and has formerly been reported to occur up to 8–12 h post-mortem (hpm). We recently described our observation of the phenomenon in up to 19 hpm in cases with in-hospital death. Due to the case selection (preceding illness, immobilisation), transfer of these results to forensic cases might be limited. We therefore examined 67 out-of-hospital cases of sudden death with known time points of death. Re-establishment of rigor mortis was positive in 52.2% of cases and was observed up to 20 hpm. In contrast to the current doctrine that a recurrence of rigor mortis is always of a lesser degree than its first manifestation in a given patient, muscular rigidity at re-establishment equalled or even exceeded the degree observed before dissolving in 21 joints. Furthermore, this is the first study to describe that the phenomenon appears to be independent of body or ambient temperature.

•Insects found at a crime scene can provide a contribution to forensic investigations.•The analysis of human genetic material obtained from entomological samples is proposed.•NGS technology was used to analyze human DNA from the gastrointestinal tract of lice.•Lice found at the crime scenes can be valuable forensic allies. Rapid and progressive advances in molecular biology techniques and the advent of Next Generation Sequencing (NGS) have opened new possibilities for analyses also in the identification of entomological matrixes. Insects and other arthropods are widespread in nature and those found at a crime scene can provide a useful contribution to forensic investigations. Entomological evidence is used by experts to define the postmortem interval (PMI), which is essentially based on morphological recognition of the insect and an estimation of its insect life cycle stage. However, molecular genotyping methods can also provide an important support for forensic entomological investigations when the identification of species or human genetic material is required. This case study concerns a collection of insects found in the house of a woman who died from unknown causes. Initially the insects were identified morphologically as belonging to the Pediculidae family, and then, human DNA was extracted and analyzed from their gastrointestinal tract. The application of the latest generation forensic DNA assays, such as the Quantifiler® Trio DNA Quantification Kit and the HID-Ion AmpliSeq™ Identity Panel (Applied Biosystems®), individuated the presence of human DNA in the samples and determined the genetic profile.

A European-wide online survey was conducted to generate an overview on the state-of-the-art using massively parallel sequencing (MPS) platforms for forensic DNA analysis and DNA phenotyping among forensic practitioners in Europe. The survey was part of the dissemination activities of the “VISible Attributes through GEnomics – VISAGE” Horizon 2020 funded European research project [30], in preparation of a series of educational training activities. A total of 105 replies from 32 European countries representing participants from police, governmental, academic, and private laboratories providing professional services in the field of forensic genetics were included in the final analysis. Of these, 73% already own an MPS platform or are planning to acquire one within the next 1–2 years. One-third of the participants have already carried out MPS-based STR sequencing, identity, or ancestry SNP typing. A total of 23–40% of participants are planning to explore all FDP applications showing the overall very high interest in using MPS for the whole range of forensic MPS markers and applications. About 50% of the participants have previously gathered experience using forensic DNA phenotyping (FDP) markers based on conventional (i.e., not MPS-based) DNA typing methods. A total of 55% of the participants have attended training on the general use of MPS technology, but 36% have received no training whatsoever. Accordingly, 90% have expressed high or medium interest to attend training on the analysis and interpretation of DNA phenotyping data for predicting appearance, ancestry, and age. The results of our survey will provide valuable information for organizing relevant training workshops on all aspects of MPS-based DNA phenotyping for the forensic genetics scientific community.

In forensic medicine, there is an undefined data background for the phenomenon of re-establishment of rigor mortis after mechanical loosening, a method used in establishing time since death in forensic casework that is thought to occur up to 8 h post-mortem. Nevertheless, the method is widely described in textbooks on forensic medicine. We examined 314 joints (elbow and knee) of 79 deceased at defined time points up to 21 h post-mortem (hpm). Data were analysed using a random intercept model. Here, we show that re-establishment occurred in 38.5% of joints at 7.5 to 19 hpm. Therefore, the maximum time span for the re-establishment of rigor mortis appears to be 2.5-fold longer than thought so far. These findings have major impact on the estimation of time since death in forensic casework.

Conjunctival petechiae are an important diagnostic finding in external examination of forensic cases, being a sign of possible mechanical compression of the neck and jugular veins (e.g. choking, strangulation). Nevertheless, it is well known, that strong congestion of the conjunctival blood vessels might lead to the development of petechiae in the perimortal and early post mortem period, e.g. due to a head down position of the body. By now it remains unclear, whether a short term horizontal prone position of a body can lead to the development of conjunctival petechiae in the early post mortem period, a situation that might occur in everyday forensic casework. Therefore, we investigated the occurrence of conjunctival petechiae in 20 deceased at <12h after death following a prone position of 2h. Petechiae developed in 8 cases. Therefore, our results for the first time give evidence that conjunctival petechiae can be observed after a short-term horizontal prone position of a body in the early post mortem period, influencing the assessment of future forensic cases. Furthermore, statistical analysis revealed significant correlations with the examination method used to ectropionise the eyelids (forceps vs. cotton swab) and preceding resuscitation attempts. The latter observations should be considered in future research on the phenomenon.