Investigating CSI – Background material Table of Contents I ...

THE KASTLE-MEYER TEST
I. HISTORY
The Kastle-Meyer test got a huge start from Louis-Jacques Thenard and
Christian Freidrich Schonbein. Thenard discovered hydrogen peroxide in 1818,
and Schonbein developed one of the first presumptive tests in 1863. (Source:
http://www.forensicdna.com/Timeline.htm ) This test was based on the
observation that the peroxidase-like activity in hemoglobin causes oxidation of
hydrogen peroxide. The result of the reaction between hydrogen peroxide and
hemoglobin is the appearance of “foaming” as the oxygen bubbles rise. (Perhaps
you have seen this reaction yourself when washing out a cut with peroxide.)
Shonbein reasoned that if an unknown stain foamed when hydrogen peroxide
was applied to it, then that stain probably contained hemoglobin, and therefore
was likely to be blood.
Schonbein
Louis-Jacques Thenard Christian Freidrich
In the early 1900’s, Dr. Kastle developed a presumptive test for hemoglobin
which used phenolphthalein (feen-awl-THAY-leen) as a color indicator. A few
years later, Dr. Meyer refined and improved upon this test, and this is why it is
sometimes called the Kastle-Meyer test.
II. STRENGTHS AND LIMITATIONS
When discussing various presumptive tests, it is useful to know two terms in
particular: sensitivity and specificity. Sensitivity refers to the dilution factor of
a substance (in this case, blood) that can still be detected by the test. The
sensitivity of the KM test is approximately 1:10,000. This means that if one drop
of blood were added to ten thousand drops of water, the KM test would still give
a reaction to that drop of blood!
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