Overview
The determination of highly decomposed or even skeletal remains, which can provide clues and limit the scope of investigation for the source of the remains, is one of the important topics in forensic medicine research. This is especially true in cases involving juvenile crime. A further practical benefit in forensic practice is the calculation of the suspect's age based on the biological evidence that is present at the scene.
Individual age estimates have historically been based on the aging-related changes in the physical and chemical properties of different materials found in tissues like bones and teeth, as well as the physical and chemical traits of the tissues themselves. This procedure is frequently constrained or unreliable, nevertheless, whether the forensic sample is made up of broken tissue, hair, or stains. As molecular biology has advanced, a number of markers associated with growth and aging have been found at the molecular level. These markers, primarily the following four, have new ideas and directions for the estimation of the age of forensic samples and are being tested as potential markers for age determination.
De-enantiomerization of amino acids
All of the amino acids produced by the human body are L-optical isomers, but over time, this process of de-enantiomerization causes L-amino acids to gradually change into D-isomers. This process is particularly pronounced in tissues like bones, teeth, crystalline lenses, intervertebral discs, and lungs, which are formed early and slowly updated. Determining the ratio of L- and D-amino acids in tissues can be one of the research topics for forensic age estimation because the ratio of L- and D-amino acids changes continuously with age.
The telomere DNA's length
Telomeres, a unique structure at the end of the linear chromosome in eukaryotic cells, are essential for several processes, including genome stabilization, chromosome termini protection, chromosome localisation in the nucleus, and cell replication control. The growth of cell divisions is frequently accompanied by the growth of an organism's age as the number of cell divisions increases and telomere length decreases, offering a method of age assessment based on molecular-level detection of tissue cells and offering a potential remedy to the issue of age assessment of forensic evidence.
Injury to the mitochondria
The buildup of free radicals within tissue cells grows as an individual gets older. Free radicals have an oxidizing action and harm DNA through oxidation. Since mitochondrial DNA is not protected by proteins, it is more prone to deterioration. Despite the fact that the body can repair free-radical damage, this capacity declines with age. It can be used as an index for age inference by identifying the right mitochondrial damage markers.
Methylation of DNA
Additionally, there is a connection between a person's age and DNA methylation. These epigenetic changes have a significant impact on how cells and organs age. Multiple methylation sites have been linked to aging in a linear fashion, and methylation levels in DNA can rise or fall with age depending on the tissue.
The molecular biology approach to age inference not only overcomes the constraints of conventional morphological age inference, but also makes it possible to estimate age using a variety of trace specimens. However, the area faces various challenges, chief among which is the vulnerability of observation indicators to environmental, genetic, and disease-related factors, as well as variations between populations and organs. Given the variety of index detection techniques, it is also essential to standardize experimental practices and build laboratory quality control systems.
These molecular biology indices are connected despite the fact that they have inherent limitations. It is possible to develop formulas for quantifying aging-related deterioration and gain a better understanding of the molecular causes of aging by integrating various indicators and building an aging network. This goal will be accomplished as experimental methods develop further.
