spdx-forensic sero

• Forensic serology


  Utilized to assess a presence of blood, semen or saliva on a suspected stain
• Forensic studies or Forensic Medicine


  Find out someone's DNA
• Serology


  Preliminary test for most of the forensic medicine because serology is known to be fast, efficient and inexpensive compared to DNA analysis. It saves much time and effort by identifying the biological fluid stains that might be present
• Avoid performing DNA analysis for non biological materials
• The Major Body Fluids

  • Blood
  • Semen
  • Saliva
• Blood


  • Tissue composed of plasma. Plasma consists of about 90% water and 10% of a long list of other substances (7% protein, 3% urea, amino acids, carbohydrates, organic acids, fats, steroid hormones, and other inorganic ions)
  • Erythrocytes (red blood cells)
  • Leukocytes (white blood cells), and platelets
• Hemoglobin


  Can be utilized to assess the presence of blood in the stain that is suspected
• ABO Blood Group


  The first and best known class of antigens produced by allelic genes on the specific locus or loci of chromosomes and inherited independently of other genes. Genetically controlled and invariant throughout a person's life, blood groups are a robust biological marker. The letters A, B, and O refer to the antigens on the surface of the red blood cells
• Presumptive Tests


  React with the hemoglobin present in blood. If hemoglobin is present, one of two general results occurs, depending on the test. Narrow possibilities and help decide which test to do next. Can be used on larger areas. Can locate evidence not visible to the naked eye. Are fairly sensitive and have a higher risk of false positives. Colorimetry, Fluorescence, or Chemiluminescence
• Colorimetric Tests


  The testing chemical is added to the suspected stain and then an oxidant is added, usually 3% hydrogen peroxide. Catalytic color tests are phenolphthalein, benzidine, leucomalachite green, and Tetramethylbenzidine (TMB). Phenolphthalein is used more often than the other tests. The sensitivity of the phenolphthalein test can detect blood diluted down to 10-7 (1 part in 10 million) and even decades-old bloodstains can yield positive results. Phenolphthalein is cross-reactive with other substances, such as some vegetables. Also known as Kastle Meyer Test
• How to perform Colorimetric Test

  Moisten a clean cotton swab with distilled water and rub it on the suspected stain. Add a drop of phenolphthalein solution to the swab's tip; it should remain colorless. Add a drop of hydrogen peroxide (3%); if the tip turns pink, the test is presumptively positive for blood. If the swab tip remains colorless, then the result is negative for blood. The hydrogen peroxide would continue to react with the hemoglobin and degrade it if it were not for an enzyme called catalase found primarily in red blood cells that destroys hydrogen peroxide and frees water and oxygen; this makes the local pH more basic and turns the phenolphthalein pink. The color change must be within several seconds because the tip may turn pink through normal oxidation after several minutes' exposure to air.
• Luminol


  Also known as (3-aminophthalhydrazide) or Albrecht Reaction. Reacts in the presence of hemoglobin, much like phenolphthalein, when an oxidizer is applied. The reaction, however, results in a blue-white to yellow-green luminescence (light emitted as a byproduct of a chemical reaction) if blood is present. Very sensitive to hemoglobin and will detect blood in dilutions of 1 in 5,000,000. Does not affect polymerase chain reaction (PCR) of DNA. Luminol, a suitable oxidant, and water are mixed and sprayed over the area of interest. The pattern will be visible for up to 30 seconds before additional treatment is required; overspraying, however, will result in "bleeding" of the patterns and a loss of detail. Does not significantly affect presumptive, confirmatory, species origin, and ABO tests. Does interfere with some enzyme and protein genetic marker systems, such as acid phosphatase, esterase D, peptidase A, and adenylate kinase.
• Fluorescein


  Another chemical that is used to check for the presence of blood. Prepared much in the same way as luminol except that the commercial preparation contains a thickener. Stays on the surface better than luminol, making it easier to use on walls and other vertical surfaces. Produces fluorescence and must be illuminated at 450 nanometers via an alternate light source (ALS) to be seen. Both luminol and fluorescein are characterized as irritants but are not known to be carcinogens. Nevertheless, safety precautions and protective equipment should be employed during their use.
• Confirmatory Tests for Blood

  Formation of crystals through the application of heat and testing chemicals. Ex. Takayama test (also known as the hemochromogen test): 1. Sample of the presumptive stain is placed under a cover slip. 2. Sample is heated briefly and observed through a microscope. Pyridine under alkaline conditions in the presence of a reducing sugar is added with a pipette. Heating the sample properly is key: Even when blood is present, improper heating of the sample can result in a false negative. The Takayama test is very sensitive, and even very old bloodstains may give a positive reaction. 3. If blood is present, salmon-colored crystals form.
• Most forensic laboratories today do not conduct confirmatory tests for blood—the sample, if presumptively positive, will go straight to the DNA unit.
• If the tests mentioned above are not available, a sensitive and simple test card (such as the ABAcard, HemaTrace) is a cost-effective way to confirm blood on a stain too small for DNA analysis. Disadvantages: can cross react with some animal blood.
• Semen


  A complex gelatinous mixture of cells, amino acids, sugars, salts, ions, and other materials produced by post-pubescent males and is ejaculated following sexual stimulation. The volume of ejaculate varies from 2 to 6 milliliters and typically contains between 100 and 150 million spermatozoa, or sperm cells, per milliliter. The presence of semen (or, by extension, intact sperm) is considered presumptive evidence of sexual contact.
• Presumptive Tests for Semen

  Detection of acid phosphatase. Semen contains acid phosphatase (AP), a common enzyme in nature that occurs at a very high level in semen. This allows for a test, with a high acid phosphatase threshold, to presumptively identify semen. The most common test is Brentamine Fast Blue B applied to the sample on an alphanaphthyl phosphate substrate. A positive reaction results in a purple color. Brentamine Fast Blue B is a known carcinogen and must be handled accordingly. A piece of filter paper or cotton swab is moistened with sterile water and applied to the questioned stain. The reagent is added, and if an intense purple color is seen, the test is positive; if no color reaction occurs within 2 minutes, the test is negative. If a sample is known or suspected to be "old," a negative result should be cautiously interpreted because AP becomes less active over time. Positive results are presumptive, because many biological fluids, including vaginal secretions, contain some amount of AP. Commercial test kits are available for semen.
• One Step Method for Presumptive Semen Test

  Apply a drop of the combined reagents to the unknown sample. A purple color that develops within 60 seconds is a positive reaction.
• PSA (Prostate Specific Antigen)


  Also known to be a tumor marker and could only be found on male. (p30) ELiSA; detection level as low as 0.005 ng/mL. Principle involved: based on antigen antibody reaction.
• ALS (Alternative Light Source)


  Used for presumptive semen test
• ABA Semen Detection Card

  Used for presumptive semen test
• Confirmatory Tests for Semen

  Detection of acid phosphatase. Traditional method for sperm identification is to use the Christmas tree stain: (+) Sperm head turns pink, middle portion blue, tail yellow-green. Skin cells will stain green to blue-green. An extract of the stain is dissolved in water, and then a portion is applied to a microscope slide, heat-fixed, and then colored with the Christmas tree stain. The slide is then scanned at magnifications of 400 to 1000. Even if detached sperm heads are the only structure on the slide, and the Christmas tree stain assists in distinguishing them, this is still confirmative for the presence of semen. Phase contrast or dark field microscopy may also be used. The hematoxylin-eosin stain is also used but operates on the same premise (the stain colors are purple for heads and pink for the rest).
• Saliva


  Saliva can be evidence in a number of crimes. Bite marks, licked adhesives (like envelopes and stamps), eating and drink surfaces, or even expectoration (spitting) can yield important DNA evidence. Saliva stains may be difficult to see, and detection can be tricky. The problem is that although the Enzyme amylase occurs in saliva, and tests exist for amylase; amylase also occurs in many other body fluids. It occurs in higher amounts in saliva, so the intensity of a test result could be considered presumptively positive for saliva. Saliva has large amounts of skin (epithelial) cells from the inner cheek walls and therefore is easy to type for DNA analysis.
• Phadebas Test


  Used to detect the presence of saliva.
• Presumptive Test


  Often used, highly sensitive to but not specific for a particular substance. For example, a color test may indicate that a stain may be blood, but not what kind of blood (human or non-human). Utilized to establish the possibility of the specific bodily tissue or fluid is present. It may even give a false positive result; that is, the substance may not be blood but something that reacts with the chemicals used in the test. The idea of presumptive tests is that some false positive results are acceptable as long as no false negative results are obtained. The presumptive positive results can be more specifically tested with the second type of test, a confirmatory test.
• Nowadays, presumptive is performed and then followed by DNA analysis
• Confirmatory Test


  Tests positive for the substance in question and only that substance. Can identify specific biological material but lack sensitivity, in that a relatively large amount of the substance must be available for the test to be positive, but it might give few false negatives because the amount is insufficient.
• The presumptive/confirmatory test structure allows crime scene and laboratory personnel to sort potential evidence into processing categories, such as "Test for DNA" and "No DNA Testing".
• About 20 human blood groups are known to exist.
• Specimen used in blood typing

  Aliquot of packed red cells
• Forward/direct blood typing


  Usually used in the laboratory for routine blood typing. Using aliquot packed red cells and reagents (commercial antisera A and B). Principle: Agglutination
• Reverse/back typing


  Serum is utilized because antibodies are present in serum. Reagent used are known cells (Known A and Known B). Principle: Agglutination. Can be used to counter check or cross check results for forward typing.