Nails as a primary sample type for molecular genetic identification of highly decomposed human remains

Tendons and table salt: A recipe to preserve human DNA

For disaster victim identification, hundreds of samples of human remains have to be extracted from human bodies rapidly for later DNA analysis, often in situation with high humidity, high temperature and no access to cooling facilities. Genetic typing of these samples may be challenging due to degradation of DNA. Until today, bone and teeth are the preferred biological matrix for genetic identification of decomposed human remains. However, processing these samples is time and cost consuming. To address the challenges associated with workload, finances, and sample preservation in the genetic identification of unknown dead bodies, we tested 44 hand and foot tendons from deceased with advanced post mortem changes as alternative DNA material. In addition, we examined commercially available table salt as potential preservation method with 10 tendons over a period of 12 months. The parameters external appearance, DNA quantity and quality have been analysed. Overall, 39 of 44 tendons examined yielded valuable DNA profiles with at least ten autosomal STR loci. Storage in table salt not only increased DNA yield but also resulted in high quality STR profiles of the preserved tendons throughout the study period of 12 months compared to storage without salt. According to the results of this study, we recommend hand and foot tendons as alternative DNA material from bodies with advanced post mortem changes. We particularly recommend commercially available table salt as a storage medium for the preservation of DNA samples. Under field conditions without cooling facilities and the need to store samples prior to DNA analysis table salt is a good storage medium: it preserves DNA and is easily available.

The Role of Fingernails in Death Investigation

ABSTRACT

In forensic pathology, forensic onychology studies fingernails and toenails for medicolegal purposes. It mainly deals with DNA profiling from nails, toxicological analysis for detecting poisons, and the collection of trace evidence present under the nails. Injuries to fingernails and their interpretation for medicolegal purposes are the neglected areas of this study. We have discussed the most common types of fingernail injuries and their significance. We found that their notification has significant value in drowning cases, defense wounds on the palm, self-inflicted cuts, burns, electrocution, blunt trauma, physical assault, sexual offenses, and other issues like torture. We emphasize the examination of fingernails in the autopsy and medicolegal clinical examination for better administration of law and justice.

Nails as optimal source of DNA for molecular identification of 5 decomposed bodies recovered from seawater: from Y-ancestry to personal identification

Molecular identification of extremely compromised human remains in forensic field is usually performed from DNA typing of bones, which are a difficult sample to work with. Moreover, autosomal STR profiles do not always result in the identification of the donor due to lack of comparisons or non-hit throughout database searching. An attempt to overcome these issues is represented by fingernails as an alternative DNA source and Y-STRs typing to infer both geographical and familial ancestry of the unknown donor. In this study, we analyzed both 24 autosomal and 27 Y-chromosome STRs from unidentified human remains (UHRs) of five males recovered from the water near the southwestern coast of Sardinia by the Italian Harbor Master's Office. Nail clippings provided an optimal source of autologous DNA for molecular identification in a very short time, producing complete autosomal and Y-STR profiles even under conditions of high body degradation. Unfortunately, no match neither compatibility occurred using autosomal STRs (aSTRs), initially. Upon analyzing the Y-haplotypes, we found out they had already been observed in northern Africa, providing us important investigative leads. This prompted the International Criminal Police Organization (INTERPOL) to provide us with references of alleged relatives that were then confirmed to be related. The use of fingernails represents an excellent DNA source especially for genetic identification of decomposed bodies recovered in seawater environment. Notably, DNA extracted from nails gave high-quality Y-STR haplotypes by which predicting paternal ancestry of the unidentified donors may result fundamental in the forensic investigative context.

Age determination through DNA methylation patterns in fingernails and toenails

Over the past decade, age prediction based on DNA methylation has become a vastly investigated topic; many age prediction models have been developed based on different DNAm markers and using various tissues. However, the potential of using nails to this end has not yet been explored. Their inherent resistance to decay and ease of sampling would offer an advantage in cases where post-mortem degradation poses challenges concerning sample collection and DNA-extraction. In the current study, clippings from both fingernails and toenails were collected from 108 living test subjects (age range: 0-96 years). The methylation status of 15 CpGs located in 4 previously established age-related markers (ASPA, EDARADD, PDE4C, ELOVL2) was investigated through pyrosequencing of bisulphite converted DNA. Significant dissimilarities in methylation levels were observed between all four limbs, hence both limb-specific age prediction models and prediction models combining multiple sampling locations were developed. When applied to their respective test sets, these models yielded a mean absolute deviation between predicted and chronological age ranging from 5.48 to 9.36 years when using ordinary least squares regression. In addition, the assay was tested on methylation data derived from 5 nail samples collected from deceased individuals, demonstrating its feasibility for application in post-mortem cases. In conclusion, this study provides the first proof that chronological age can be assessed through DNA methylation patterns in nails.

Suitability of specific soft tissue swabs for the forensic identification of highly decomposed bodies

When decomposition of a recovered body is fairly advanced, identification based on common morphologic features is often impossible. In these cases, short tandem repeat (STR) marker genotyping has established itself as a convenient and reliable alternative. However, at very progressed stages of decomposition, postmortem tissue putrefaction processes can decrease DNA yields considerably. Hence, not all types of tissue are equally suitable for successful STR marker-based postmortem identification. Bone or dental material is often analysed in corpses with advanced decompositional changes. However, processing of these materials is very elaborate and time and resource consuming. We have therefore focused on the suitableness of various types of soft tissue swabs, where DNA extraction is easier and faster. By sampling 28 bodies at various stages of decomposition, we evaluated the suitability of different tissues for genotyping at varying degrees of physical decay. This was achieved by a systematic classification of the sampled bodies by morphological scoring and subsequent analysis of multiple tissue swabs of the aortic wall, urinary bladder wall, brain, liver, oral mucosa and skeletal muscle. In summary, we found variable degrees of suitability of different types of soft tissue swabs for DNA-based identification. Swabs of the aortic wall, the urinary bladder wall and brain tissue yielded the best results - in descending order - even at advanced levels of decay.

Comparative analysis of DNA extraction processes for DNA-based identification from putrefied bodies in forensic routine work

Identification of putrefied bodies is an important and common task in forensic routine. Usually, the identification of deceased is done by visual recognition, fingerprints, physical distinguishing marks (e.g. tattoos, scars and surgical implants) and/or dental examination. However, if morphologic characteristics are not recognizable, due to advanced putrefaction of the corpse, or recent medical records are not available, the DNA-based identification is favored. Thus, in order to find another reliable procedure for DNA extraction of putrefied samples regarding tissue selection, costs and time, two commercial forensic kits were compared: DNeasy® Blood & Tissue kit and SwabSolution™ kit. Both kits were used for DNA extraction from five soft tissues (brain, aorta, liver, kidney and psoas major muscle) and nails (finger- and toenail) obtained during the medicolegal autopsy of 20 putrefied corpses. DNeasy® Blood & Tissue kit was by quantitative comparison mostly superior to SwabSolution™ kit: it yielded more DNA of better quality (i.e. less degraded and inhibited). However, the qualitative results (DNA profiles) of both extraction procedures were similar. Among the analyzed tissue types, nails were proved as the most suitable for DNA-based identification of putrefied bodies.