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