Kastle–Meyer test

A presumptive blood test used in forensic science

The Kastle–Meyer test is a presumptive test used in forensic science to detect the possible presence of blood. It is based on the peroxidase-like activity of hemoglobin in blood, which catalyzes the oxidation of phenolphthalin to phenolphthalein, resulting in a pink color change.

Joseph H. Kastle, co-developer of the Kastle–Meyer test

History

The test was developed in 1901 by Joseph H. Kastle and S. R. Meyer. Joseph Kastle was a prominent chemist known for his work in biochemistry and toxicology. The Kastle–Meyer test was one of the first forensic tests to be widely used for the detection of blood at crime scenes.

Principle

The Kastle–Meyer test relies on the catalytic properties of hemoglobin, which acts similarly to peroxidase enzymes. When a sample suspected of containing blood is treated with the Kastle–Meyer reagent, which contains phenolphthalin, and then exposed to hydrogen peroxide, the hemoglobin catalyzes the oxidation of phenolphthalin to phenolphthalein. This reaction produces a bright pink color, indicating the presence of blood.

Procedure

The procedure for the Kastle–Meyer test is as follows:

1. A small sample of the suspected stain is collected using a swab or filter paper. 2. A drop of the Kastle–Meyer reagent is applied to the sample. 3. A drop of hydrogen peroxide is added to the sample. 4. Observation for a color change to pink, which indicates a positive result for the presence of blood.

Limitations

While the Kastle–Meyer test is highly sensitive and can detect blood at very low concentrations, it is not specific to human blood. Other substances, such as certain vegetable materials and animal blood, can also produce a positive result. Therefore, the test is considered presumptive and must be followed by more specific tests, such as DNA analysis, to confirm the presence of human blood.

Applications

The Kastle–Meyer test is widely used in crime scene investigations to quickly screen for the presence of blood. It is valued for its simplicity, rapid results, and the minimal amount of sample required. The test is often used in conjunction with other forensic techniques to build a comprehensive understanding of the evidence.

Related pages

• Forensic science
• Presumptive test
• Bloodstain pattern analysis
• DNA profiling