Raman spectroscopic method for semen identification: Azoospermia.

Semen evidence can be of critical importance in assault cases. In the past, semen confirmatory tests relied solely on the presence of sperm. However, current semen tests rely on the detection of proteins in the seminal fluid because some semen contains no sperm, a condition called azoospermia. Our laboratory has been developing a Raman spectroscopic test for identification of dry traces of body fluids, including semen, for forensic purposes. An automatic software has already been built for differentiating all the main body fluids (Muro et al., 2016). The main objective of this study was to evaluate the ability of Raman spectroscopy to identify semen traces in the absence of sperm. For this purpose, a comparative analysis of Raman spectra of semen, seminal fluid and sperm samples obtained from several donors was conducted. It was determined that the contribution of seminal fluid dominates the Raman spectra of semen. This was further confirmed by analyzing Raman spectra of semen obtained from a donor who had had a vasectomy. All of the individual spectra from seminal fluid and azoospermatic semen were correctly identified with a previously made chemometric model as semen. It was concluded that the presence of sperm is not necessary for the correct identification of semen using Raman spectroscopy and chemometrics. This further demonstrates the great potential of Raman spectroscopy as a universal tool for confirmatory identification of all main body fluids for forensic purposes.