Vomit identification by a pepsin assay using a fibrin blue-agarose gel plate

Reported is a simple and reliable method for identifying the presence of gastric fluid in forensic samples by an assay that reveals the pepsin activity. These samples are usually vomit found at the scene of a crime, either in fresh form or as a dried stain on clothing. The pepsin within the sample is assayed for its proteolytic activity which is revealed in a fibrin blue-agarose gel plate, as a result of an enzymatic reactivity that takes the form of a concentric, blue, translucent ring around the tested sample. Apart from being able to determine the pepsin content of fresh or recent forensic samples, this method has also achieved positive reactions in aged gastric fluid stains that were kept at room temperature. No body fluids other than the gastric fluid and no proteolytic enzymes other than pepsin show a positive reaction with the use of this method. This method has an additional advantage, in that the enzymatic activity seen on the gel plate can be photographed and the gel plate, on drying, can also be preserved as evidence.