Government of Ontario

CFS - Technical Information Sheets - Biology - Saliva Information

Centre of Forensic Sciences

Technical Information Sheets

Biology


Saliva Information – PDF, 30 kb (Rescinded Sept. 17, 2012)


Introduction

Amylase is a substance used in the digestion process to break down starch. It is usually found at high levels in saliva but is also present in other body fluids, though normally at much lower levels.

Examination for the Presence of Amylase

An item is examined visually for the presence of staining. Areas that contain amylase are localised on an item using a Phadebas™ press test. A Phadebas™ tube test can be used to measure the level of amylase.

Tests For The Presence Of Amylase

Visual examination
May involve using a stereomicroscope (a magnifying tool) and enhanced light sources.

Phadebas™ press test
A test used to localise amylase-containing stains on an item. Filter paper coated with the Phadebas™ reagent is dampened and placed in firm contact with the item. A blue colour indicates the location of amylase.

Phadebas™ tube test
A test using the same chemical but carried out in a test tube. The intensity of blue colour is measured and interpreted.

Limitations
The finding of amylase is not proof of the presence of saliva. It is found at low levels in other body fluids such as perspiration, vaginal secretions and semen. In addition, amylase can sometimes be found at high levels in faeces. Therefore, interpretation of amylase results will be dependent on the level of amylase detected as well as the location of the stain and the possible presence of other body fluids.

A negative Phadebas™ test does not necessarily mean that saliva is absent. Low levels of amylase may not be detectable using the Phadebas™ test.

Amylase is water-soluble and can therefore be lost through contact with water (e.g., laundering).

Amylase levels do not correlate to the potential quantity of DNA contained within a sample.

Amylase is not human-specific.


Glossary

Amylase
A substance used in the digestion process to break down starch.

Phadebas™ reagent
A commercially manufactured chemical that in the presence of amylase produces a blue colour. The intensity of colour relates to the level of amylase present.

Saliva
A watery secretion found in the mouth that moistens the mouth, lubricates chewed food and aids in digestion.