Analytical approaches for bloodstain aging by vibrational spectroscopy: Current trends and future perspectives

The estimation of bloodstain aging is one of the most challenging errands in crime scene investigation. Blood is one of the most frequently found physical evidence in a violent crime scene as it conveys crucial information. Blood often discovered in different forms, i.e., pool of liquid, dried stains, and dried pool adhere to various surfaces such as clothing, metals, plastic, cellulose rubber, etc. or mixed with numerous environmental contaminants or other body fluids. Significant studies were carried out to estimate the bloodstain aging since 1907. With new developments in late 20th century, Spectroscopy was first introduced in the bloodstain aging analysis in 1960. Spectroscopic techniques are more reliable and appropriate for forensic analysis of bloodstains due to their non-destructive and rapid nature. Since the beginning of the new millennium, Vibrational spectroscopy has been the most frequently explored technique for biological stain analysis. It is a combination of Infrared absorption and Raman scattering of electromagnetic spectrum (EMS) in the infrared region that produces multivariate spectral data of biological stains. In combination with this technique, Chemometrics portrays a vital role in the entire process of age estimation. The bloodstain aging produces multiple significant information related to crime, and it is extremely effective in crime scene reconstruction. This article exhaustively reviews all the Vibrational spectroscopic techniques for bloodstain age estimation with their limitations and future perspectives. It also compares this technique with existing spectroscopic and other instrumentation methods.