DNA analysis of hairs in a suspected case of child abuse

DNA and protein analyses of hair in forensic genetics

Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.

Frequency of biological non-skeletal materials in dry bone scenarios

In forensic anthropology, many small biological non-osseous materials may be found associated to skeletonized remains and can provide crucial information to the biological profile. Indeed, their careful recovery and correct identification can add information related to age-at-death, sex, ancestry, health, diet, migration and habits, and may be used in specific analysis such as DNA typing. However, and despite their potential, little is known about these non-osteological materials. Indeed, how frequent are they in dry bone cases? To answer this question, 100 skeletal remains with postmortem intervals ranging from 23 to 76 years from the CAL Milano Cemetery Skeletal Collection were meticulously examined for the presence of non-skeletal materials and in particular ossified cartilage, vascular calcifications, hair and nails. As a result, non-skeletal materials were found in 81 skeletal remains and showed high frequencies of recovery, despite the less-than-optimal conditions of exhumation of the skeletons. The high frequencies of non-skeletal materials obtained demonstrate the need for additional training and research given their informative power in forensic cases.

Genotyping genetic markers from LCN and degraded DNA by HRM and their application in hair shaft

Degraded and low copy number (LCN) DNA samples are common challenging materials in forensic casework because they increase the difficulty of sample processing and reduce the possibility of obtaining genetic information from DNA. High-resolution melting (HRM) curve analysis is promising for genotyping genetic markers and has been applied to the detection of LCN and degraded DNA in the field of forensic science. However, the exact assessment based on HRM at multiple genetic markers from both degraded and LCN DNA materials has not been optimized. To explore the ability of HRM to genotype LCN and degraded DNA samples, we selected three genetic markers to genotype in experimental LCN and degraded DNA and practical hair shaft materials, which are often encountered as degraded and LCN DNA in forensic medicine. The results show that DNA samples of as low as 100 pg and as short as 60 bp were successfully genotyped by the HRM assay at all three genetic markers, whereas in hair shaft DNA, two loci were accurately genotyped. The HRM assay established in this study can be applied to LCN and degraded DNA analysis in forensic casework and can act as a reference point before genotyping short tandem repeat markers. Developing the HRM strategy for genotyping DNA genetic markers enriches detectable targets in hair shaft samples and provides valuable data for further exploration.