Government of Ontario

CFS - Technical Information Sheets - Biology - Blood Information

Centre of Forensic Sciences

Technical Information Sheets

Biology


Blood Information - PDF, 29 kb (Rescinded Sept. 17, 2012)


Introduction

Blood is a liquid that circulates through the body, transporting oxygen and nutrients and removing waste products. Blood consists of a liquid called plasma in which blood cells are suspended. Hemoglobin is a component of blood.

Examination for the Presence of Blood

Items are visually examined for any staining that may contain blood. Stains are tested using the Kastle-Meyer test. Stains may also be tested using an ABAcard® to determine whether or not they are of human origin.

Tests for the Presence of Blood

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

Kastle-Meyer test (Phenolphthalin test) : A 3-stage chemical test that gives a pink colour reaction in the presence of haemoglobin, a substance specific to blood. This can be performed as a rub or direct test.

ABAcard®, HemaTrace® test: Test used to determine if a bloodstain is of human origin. This test uses commercially prepared reagents that bind specifically to human (higher primate) hemoglobin, allowing for visual detection.

Limitations

The sensitivity of the Kastle-Meyer testing is such that a positive result may still be obtained in the absence of visible staining.

Although false positive Kastle-Meyer reactions are sometimes obtained with other substances, such as certain fresh plants, as applied at the CFS this test is specific for blood. The Kastle-Meyer test alone does not indicate whether or not the blood is of human origin.

The ABACard® HemaTrace® test is specific to human (higher primate) blood. False negative results are possible when dealing with severely degraded samples. False positive results have been observed with ferret blood.

Glossary

Direct test - Involves applying the Kastle-Meyer chemicals directly to a sub-sample from the area in question.

Hemoglobin - The component of blood that transports oxygen.

Rub test - Involves rubbing the area in question with paper and applying the chemicals to the paper.