What is a Kastle-Meyer test used for in forensic science?
The Kastle-Meyer test is a quick inexpensive test used to analyze evidence at a crime scene for the presence of blood. Phenolphthalein reacts with hydrogen peroxide in the presence of hemoglobin to turn from colorless to pink.
How does the Kastle-Meyer test test for blood at a crime scene?
A presumed blood sample is first collected with a swab. A drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. If the swab turns pink rapidly, it is said to test presumptive positive for blood.
How does Kastle-Meyer test work?
The Kastle-Meyer colour test works on a similar principle to Luminol, with an active compound which reacts with hydrogen peroxide in the presence of blood. In this case the chemical involved is phenolphthalein. This will react with hydrogen peroxide in the presence of haemoglobin to produce a pink colour.
What is the Kastle-Meyer test and what is the scientific background on how it works?
The Kastle-Meyer solution is a phenolphthalein indication solution which has been reduced, usually by reacting it with powdered zinc. The basis of the test is that the peroxidase-like activity of the hemoglobin in blood catalyzes the oxidation of the colorless reduced phenolphthalein into bright pink phenolphthalein.
Why do we perform Kastle Meyer before other forensic test?
Why would we perform the Kastle-Meyer test before other forensic tests? The Kastle-Meyer test is a presumptive test for blood. It is fast, easy, and cost-effective, so it is performed before other tests. However, since it has a high rate of false positives, the results must be confirmed with further testing.
What does a Kastle Meyer blood test do quizlet?
The Kastle-Meyer test is a presumptive blood test, first described in 1903, in which the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. If there is blood present, a dark pink color is produced.
What is the Kastle-Meyer test quizlet?
In which scenario would you use a Kastle-Meyer test?
Blood presumptive tests, such as the Kastle-Meyer (KM) test and Hemastix, are commonly used in forensic casework to determine the possible presence of blood if, for example, a red-brownish stain is found on a garment.
What is an advantage of the Kastle-Meyer test?
The Kastle-Meyer test is an ideal presumptive test for blood because it is fast, it is highly specific for blood, and it can reliably detect blood in dilute samples. However, there are a few chemicals that react with phenolphthalein to produce a false positive (e.g. iron and copper oxides).
What tests do forensics use to test blood?
The crime scene team uses an immunochromatographic procedure for the qualitative indication of human blood. At crime scenes, such testing is intended for selective use when human origin of suspected bloodstains is questionable and/or when the determination of indication of human origin is time sensitive.
What is the purpose of ethanol in the Kastle Meyer test?
The Ethanol component is used to lyse the cells present and gain increased sensitivity and specificity.
How is the Kastle Meyer test for blood performed quizlet?
Kastle-Meyer test: A blood sample is collected on a cotton swab and a clear solution, consisting of a reduced form of phenolphthalein and hydrogen peroxide is applied, turning pink in the presence of blood.
Why do we perform Kastle-Meyer before other forensic test?
How accurate is the Kastle-Meyer test?
Also according to the results presented here through the sensitivity test, the Kastle-Meyer Reagent was able to detect the presence of blood in the samples up to the dilution of 1:10,000 in human and dog, but not in 1: 100,000, as in previously described results, while cat blood was detectable up to a 1: 1,000 dilution …
How do forensic scientists detect blood?
Large areas at crime scenes can be scanned using Luminol with no ill effects on blood. Blood stains are readily enhanced by Luminol which allows for an interpretation of blood stain patterns. A question associated with the use of Luminol, however, is with what other chemicals or substances Luminol reacts.
How is forensic testing done?
Forensic pathologists conduct postmortem examinations on body tissues, blood, and/or other bodily fluids collected during an autopsy or from the crime scene and interpret the findings to determine the cause, the manner, and the time of death, and in some instances, to establish the identity of the deceased.
What is Kastle Meyer solution?
Kastle–Meyer reagent contains reduced phenolphthalein indicator in a basic solution. Simply wipe a presumptive bloodstain with a cotton swab, add a drop of the reagent, and then apply a drop of hydrogen peroxide. If the swab turns pink rapidly, it is positive for blood!
What are the advantages and disadvantages of the Kastle-Meyer test?
Advantages – sensitive, definitive test, low false positive test ii. Disadvantages – expensive, time-consuming 3. Testing crime scene samples for blood a. The Kastle-Meyer Test is a presumptive test for blood i.
How sensitive is the Kastle-Meyer test?
During the direct tests, Kastle Meyer showed a higher sensitivity, detecting blood down to a dilution of 1:16,384, one order of magnitude lower than Hemastix.
What are 2 examples of tests that can be done to detect blood at a crime scene?
Presumptive Tests
- Phenolphthalein Test. Also known as the Kastle Meyer Test.
- Luminol Test. How it works: A chemical compound, known as Luminol, is used in solution or sprayed onto suspected surfaces.
- Alternative Light Sources.