Chapter 15: Identification of Saliva

The foundational approach centers on salivary amylase, an enzyme naturally occurring in high concentrations within saliva that catalyzes starch hydrolysis, making it the primary target for identification assays. Presumptive testing begins with basic techniques including direct visual inspection followed by more sophisticated enzymatic activity detection methods such as starch-iodine colorimetric reactions and radial diffusion approaches, which provide rapid screening capabilities but carry inherent limitations including false positives stemming from amylase present in other biological sources or certain plant materials like citrus. Because presumptive results lack sufficient specificity for forensic conclusions, confirmatory assays become essential for establishing human salivary origin with greater certainty, typically employing immunological methods such as enzyme-linked immunosorbent assay technology designed to specifically recognize human salivary alpha-amylase isoforms. The most sophisticated and conclusive identification strategies utilize molecular approaches grounded in messenger ribonucleic acid profiling, which target biomarkers and genetic sequences uniquely or predominantly expressed in salivary tissue. These nucleic acid-based methodologies represent the highest level of sensitivity and specificity currently available, enabling reliable saliva identification even in aged, degraded, or trace evidence samples where enzymatic activity may have diminished over time, thereby providing forensic examiners with definitive confirmation suitable for legal proceedings and investigative purposes.