Saliva as Forensic Evidence using Fluorescent Spectroscopy: A Pilot Study

Abstract

Introduction: Saliva lacks the drama of blood, the sincerity of sweat and the emotional appeal of tears, yet it is the ‘sine qua non’ of the oral cavity and can prove to be the most important fluid playing a vital role in forensics. Saliva deposited on the skin by the act of biting and licking can be an important source of forensic evidence. Saliva has an enzyme α-amylase, containing tryptophan which is an important aromatic amino acid constituent. This when excited at 254 nm gives a characteristic emission spectrum at 345-355 nm. Fluorescent spectroscopy method was used to detect enzyme α-amylase in forensic identification. Aim: To detect dried saliva on the human skin by fluorescent spectroscopy. Materials and Methods: This study was planned and conducted at IICT (Indian Institute of Chemical Technology) Hyderabad. It includes 20 saliva samples of volunteers, where in the investigator took a swab from the skin of the ventral surface of forearm deposited by licking on the arm and was diluted in 0.1M Potassium Chloride (KCl), which were randomly selected from the population. A control sample of water was deposited on the contralateral arm. Each sample was excited at 254 nm and emission spectrum of both saliva and water samples were recorded. Results: The emission spectra of 20 swab samples taken from dried saliva were characterised at the primary peak of 340 to 350 nm whereas the emission spectrum of water as a control was recorded at 360 nm. Conclusion: The presence of emission spectrum at 340–350 nm with excitation at 254 nm proves to be a strong indicator of saliva detection by Fluorescent Spectroscopy, deposited on the human skin and hence detection of saliva helps in further forensic investigation for identification of suspect.

Keywords

• α-amylase
• forensic dentistry
• saliva
• tryptophan