1 / 13

Microcrystalline Test

Microcrystalline Test. Christopher, Crystal, Justin, & Jimmy. How It Works. They are used as a confirmatory test They detect whether or not a sample is/contains blood and it not actually something like red paint or ketchup

ailsa
Télécharger la présentation

Microcrystalline Test

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microcrystalline Test Christopher, Crystal, Justin, & Jimmy

  2. How It Works • They are used as a confirmatory test • They detect whether or not a sample is/contains blood and it not actually something like red paint or ketchup • As opposed to a presumptive test which indicates the POSSIBILITY that the substance being tested for is present

  3. Two Types of Tests • The two tests that fall under the category of a microcrystalline test are known as the TAKAYAMA test and the TEICHMANN test Takayama Crystals

  4. Takayama Test • This test determines if the substance in question is blood. • The Takayama Test was used to determine if there was blood on the coat of a soldier from the Way of 1812. • It works by gently heating heme (dark red, non-protein, iron-coating part of hemoglobin, C34H32FeN4O4) and adding it to pyridine (C5H5N) when there is some kind of sugar present, such as glucose, in order to create pyridine ferriprotoporphyrin crystals. • This test produces brown crystals.

  5. Takayama Reaction and Crystals Takayama Reaction Takayama Crystals

  6. Teichmann Test • This test determines if there is blood present on suspected dried blood stains. • The hematin crystals begin to form when heated blood is mixed with glacial acetic acid where there is salt. • The positive result is caused by the combination of a halogen with ferriprotoporphyrin (red-brown to blue-black crystalline salt containing iron). • This test produces pink crystals that can reach up to 10 micrometers in size.

  7. Strengths • The amount of time the bloodstain has been dry does not affect the formation of the hematin crystals. • Twelve year old stains are capable of giving a positive result when tested by the Teichmann. • Bloodstains over 20 years were also able to give a positive with this test. • The sensitivity and specificity of the Takayama and the Teichmann tests are similar: both give positive results with as little as 0.001 ml of blood or 0.1 mg of hemoglobin.

  8. Weaknesses • While Teichmann crystals may not form with stains from materials such as leather, older stains have been reposted to give false negative results when tested with the Takayama Reagent. • These tests are less sensitive than other tests. • The outcomes (+) and (-), (+) means the sample is blood but the test won’t tell from what species the blood is from.

  9. Example Case #1 The body of a 27 year old was found in a wooded picnic area. Investigators searched the area and found what appeared to be a red substance near a picnic bench. Hoping it was going to be helpful in the investigation, they sent a sample to a forensics lab where they did a Takayamatest. Results showed that the substance was not blood and was ruled out as part of the crime scene.

  10. Example Case #2 Murder suspect, Carlos Ramirez’s trunk was searched and in it, a red stained T-shirt. Investigators sent the stained clothing to a forensics lab where they performed a Teichmanntest on it. Results show it was in fact blood and was sent on for further testing.

  11. Real Case State VS Allen • On 16 February and 2 March 1998, the Durham County grand jury returned bills of indictment charging Defendant with first degree sex offense, felony child abuse, and first degree murder. • Scientists performed a Teichmann test on the victim’s training pants, underwear, and sleepers. All came back negative

  12. Review Questions • What is the purpose of a microcrystalline test? • One strength of this test? • How much blood is needed to be detected by this test? • What color crystals does the Takayama test produce? The Teichmann? To test for the presence of blood. It can detect the presence of blood in stains over 20 years old. 0.001 ml of blood or 0.1 mg of hemoglobin. Takayama: brown crystals. Teichmann: pink crystals.

  13. Works Cited Bell, Suzanne, Barry A. J. Fisher, and Robert C. Shaler. Encyclopedia of forensic science. Rev. ed. New York, NY: Facts On File, 2008. Print. "Blood Identification." what-when-how — In Depth Tutorials and Information. N.p., 1 Nov. 2010. Web. 3 Apr. 2013. <http://what-when-how.com/forensic-sciences/blood-identification/>. James, Stuart H., Paul Erwin Kish, and T. Paulette Sutton. Principles of bloodstain pattern analysis: theory and practice. Boca Raton, Fla.: CRC, 2005. Print. Giannelli, Paul C. Scientific Evidence. N.p., 2012. Web. 2 Apr. 2013. <http://www.americanbar.org/content/dam/aba/publications/criminal_justice_magazine/sp12_sci_evidence.authcheckdam.pdf>. Klinkosum, Mike. North Carolina Bar Association. N.p., 29 Sept. 2010. Web. 2 Apr. 2013. <http://criminaljustice.ncbar.org/newsletters/truebilloctt10/statevgregorytaylor>.

More Related