The emerging field of forensic epigenetics

Pyrosequencing: Current forensic methodology and future applications-a review

The recent development of small, single-amplicon-based benchtop systems for pyrosequencing has opened up a host of novel procedures for applications in forensic science. Pyrosequencing is a sequencing by synthesis technique, based on chemiluminescent inorganic pyrophosphate detection. This review explains the pyrosequencing workflow and illustrates the step-by-step chemistry, followed by a description of the assay design and factors to keep in mind for an exemplary assay. Existing and potential forensic applications are highlighted using this technology. Current applications include identifying species, identifying bodily fluids, and determining smoking status. We also review progress in potential applications for the future, including research on distinguishing monozygotic twins, detecting alcohol and drug abuse, and other phenotypic characteristics such as diet and body mass index. Overall, the versatility of the pyrosequencing technologies renders it a useful tool in forensic genomics.

Comparative Study of Acute Anogenital Injury Between Consensual and Nonconsensual Postmenarche Adolescents

ABSTRACT

In Thailand, sexual activity involving those under the legal age of consent may be legally and medically problematic, even if it is consensual. Thus, differentiating anogenital injury characteristics that occur during consensual versus nonconsensual acts with adolescent female subjects could aid legal advocates and improve health care and social support for these patients. Our study included postmenarche female patients having acute anogenital injuries after consensual and nonconsensual penetration. We found that nonconsenting patients had more cases of anogenital injury than consenting (69.8% vs 55.5%), with at least 1 abrasion, contusion, laceration, labia major or minor injury, and external or internal site injury. Both consensual and nonconsensual cases had the same common sites for injury type, reflecting the same injury mechanism; prior sexual intercourse was a significant protective factor against some anogenital injury prevalence, types, and sites for both groups. Adolescents forced into nonconsensual acts had more nonanogenital injuries. Looking at factors such as age, prior sexual activity history, and use of condom and/or contraceptive pills, it is very clear that early sexual education, particularly around consent, is critically needed in Thailand for the best interests of adolescents and children so that they and/or their guardians can access the health and legal resources required.

Rapid semen identification from mixed body fluids using methylation-sensitive high-resolution melting analysis of the DACT1 gene

In forensic genetics, a suspect is assigned to a component of a DNA mixture profile, and a probabilistic interpretation is then usually performed. However, it is difficult to determine what types of body fluid the component is from. Previous studies have reported that the fourth exon of the Dishevelled binding antagonist of beta catenin 1 (DACT1) gene is hypomethylated in a semen DNA-specific manner. In the present study, we evaluated whether the DACT1 gene could be effectively used to identify semen in body fluid mixtures and were able to semi-quantify the semen DNA content in mixed fluids. Our results showed that the DACT1 gene was useful in discriminating semen from venous blood and saliva. However, the amount of sperm in semen can affect semen identification. In addition, SI (the semen DNA content index), which we developed, was useful to determine whether the semen compromised majority, almost half, or was in the minority of the components in a mixed fluid. This technique is based on the methylation-sensitive high-resolution melting (MS-HRM) technology, which is time-, cost-, and labour-effective, and could be adopted in routine criminal investigations.

Forensic Spermatozoa Detection

Semen is crucial evidence for some sex crimes, with its sole confirmation being sperm detection. The success of sperm detection is dependent on all levels of preanalytic and analytic procedures. Specimen collection must be performed by well-trained and competent forensic physicians as well as forensic nurses, with preservation done properly before laboratory transfer. Laboratory procedures should consider archival sperm identification, by visualization, with adequate amounts separated from other cells to obtain male DNA profiles. Differential extraction is robust and accepted as the forensic standard but is time consuming and may result in male DNA loss. Thus, alternative methods and microdevices have been developed. Challenges in sperm isolation from vaginal or buccal epithelium mixes and discrimination in multiperpetrator cases have been overcome by single-cell profiling; however, problems inherent in identical twin discrimination and azoospermia have yet to be solved. Epigenetics and future molecular biomarkers may hold the key; therefore, all laboratory processes must consider DNA and RNA protection. Long-term specimen preservation should be done when possible in light of future confirmatory tests.