Simplified COI barcoding of blow, flesh, and scuttle flies encountered in medicolegal investigations.

Accurate insect identification is critical to the estimation of time of colonization (TOC) and post-mortem interval (PMI) in medicolegal death investigations. DNA testing is advantageous because it enables the identification of immature specimens that may not be identified based on morphology alone. We describe here a simplified DNA barcoding method for identifying relevant species that may be implemented by forensic genetics laboratories. A cytochrome oxidase (COI) fragment is analyzed after PCR amplification with a single primer set. The method is effective for many species commonly encountered in death investigations in the USA: members of blowfly genera Calliphora, Chrysomya, Cochliomyia, Lucilia, and Phormia; members of the flesh fly genera Blaesoxipha, Oxysarcodexia, Ravinia, and Sarcophaga; and the scuttle fly Megaselia scalaris. We tested the method on specimens with verified identifications and used it to build a collection of reference sequences from specimens collected in Harris County, Texas. We show here the correct identification of larvae, pupae, and pupal exuviae from the medicolegal casework.

Postmortem genetic screening for the identification, verification, and reporting of genetic variants contributing to the sudden death of the young.

Each year in the United States, thousands of cases of sudden and unexpected deaths of infants, children, and young adults are assigned an undetermined cause of death after postmortem investigation and autopsy. Heritable genetic variants have been suggested as the cause of up to a third of sudden death (SD) cases. Elucidation of the genetic variants involved in SD cases is important to not only help establish cause and manner of death of these individuals, but to also aid in determining whether familial genetic testing should be considered. Previously, these types of postmortem screenings have not been a feasible option for most county medical examiners' and coroners' offices. We sequenced full exons of 64 genes associated with SD in the largest known cohort (351) of infant and young SD decedents using massively parallel sequencing at <$600 per sample. Genetic variants were assessed through literature review and clinical evaluation by a multidisciplinary consortium of experts. Thirteen individuals (3.7%), eight infants (2.8% of those <1 yr of age) and five children/young adults (7.0% of those >1 yr of age), were found to have a reportable genetic variant contributing to SD. These percentages represent an estimate lower than those previously reported. Overall yields and results likely vary between studies due to differences in evaluation techniques and reporting. Additionally, we recommend ongoing assessment of data, including nonreported novel variants, as technology and literature continually advance. This study demonstrates a strategy to implement molecular autopsies in medicolegal investigations of young SD decedents.

DNA testing of sexual assault evidence: the laboratory perspective.

The availability of DNA testing has dramatically changed the way that crimes are investigated. DNA results can link offenders to their crimes, exonerate wrongfully accused individuals, identify mass fatality victims and more. In the case of sexual assault, DNA evidence alone cannot prove that a sexual assault has occurred. DNA analysis can only reveal whether a person's DNA is, or is not, present. In this paper, the authors provide readers with an overview of the advantages and limitations of DNA analysis, the importance of proper evidence collection, the technologies available, and the amount of sample needed for testing. Through proper evidence collection and quality laboratory services, the full value of DNA will be realized.

UV irradiation and autoclave treatment for elimination of contaminating DNA from laboratory consumables.

Laboratories employ various approaches to ensure that their consumables are free of DNA contamination. They may purchase pre-treated consumables, perform quality control checks prior to casework, and use in-house profile databases for contamination detection. It is better to prevent contamination prior to DNA typing than identify it after samples are processed. To this end, laboratories may UV irradiate or autoclave consumables prior to use but treatment procedures are typically based on killing microorganisms and not on the elimination of DNA. We report a systematic study of UV and autoclave treatments on the persistence of DNA from saliva. This study was undertaken to determine the best decontamination strategy for the removal of DNA from laboratory consumables. We have identified autoclave and UV irradiation procedures that can eliminate nanogram quantities of contaminating DNA contained within cellular material. Autoclaving is more effective than UV irradiation because it can eliminate short fragments of contaminating DNA more effectively. Lengthy autoclave or UV irradiation treatments are required. Depending on bulb power, a UV crosslinker may take a minimum of 2h to achieve an effective dose for elimination of nanogram quantities of contaminating DNA (>7250mJ/cm(2)). Similarly autoclaving may also take 2h to eliminate similar quantities of contaminating DNA. For this study, we used dried saliva stains to determine the effective dose. Dried saliva stains were chosen because purified DNA as well as fresh saliva are less difficult to eradicate than dried stains and also because consumable contamination is more likely to be in the form of a collection of dry cells.