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FORENSIC BIOCHEMISTRY

FORENSIC BIOCHEMISTRY. BY DR. c. E.o . NEBOH (b.sc, M.sc, PH.d , Pgde , amlscn ). CRIME ?. LOOK FIND PROCESS EVIDENCE ARREST CONVICT JUSTICE !!!!!!!. INTRODUCTION.

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FORENSIC BIOCHEMISTRY

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  1. FORENSIC BIOCHEMISTRY BY DR. c.E.o. NEBOH (b.sc, M.sc, PH.d, Pgde, amlscn)

  2. CRIME ? LOOK FIND PROCESS EVIDENCE ARREST CONVICT JUSTICE !!!!!!! NEBOH EE (FORENSIC BIOCHEMISTRY)

  3. INTRODUCTION Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as silent evidence against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects - all these and more bear mute witness against him. NEBOH EE (FORENSIC BIOCHEMISTRY)

  4. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong; it cannot perjure itself; it cannot be wholly absent. Only its interpretation can err. Only human failure to find it, study and understand it, can diminish its value. • Kirk, Paul, Crime investigation John Wiley & Sons Canada, Limited, 1953 NEBOH EE (FORENSIC BIOCHEMISTRY)

  5. Every incident, be it a crime, accident, natural disaster, armed conflict, or other, leaves traces at the scene. The goal of the subsequent investigation is to correctly interpret the facts, reconstruct the events and understand what happened. • Due to the transient and fragile nature of those traces, their reliability and the preservation of their physical integrity depend to a very large extent on initial actions at the scene of the incident. NEBOH EE (FORENSIC BIOCHEMISTRY)

  6. Evidence integrity can be achieved with very limited means by observing a key set of guiding principles. • Acting with care and professionalism throughout the crime scene investigation process is critical for the admissibility of evidence for court purposes as well as for human rights inquiries and humanitarian action. NEBOH EE (FORENSIC BIOCHEMISTRY)

  7. FINGER PRINT NEBOH EE (FORENSIC BIOCHEMISTRY)

  8. Forensic Biochemistry • Forensic biochemistry is the application of biochemical analytic methods, particularly serological methods, to legal investigations. • Serology involves the investigation of bodily fluids, particularly the likes of blood, semen, saliva, all of which are commonly found at certain crime scenes. NEBOH EE (FORENSIC BIOCHEMISTRY)

  9. GENERAL STEPS IN FORENSIC ANALYSIS • Generally forensic analysis involves the following: • 1. Identification: Determination of physical –chemical composition of the evidence (eg. Illicit drugs). • 2. Classification: Determination of class, type of biological substance. (hair, fibres, blood type, DNA). NEBOH EE (FORENSIC BIOCHEMISTRY)

  10. 3. Individualization: Determination of unique identity of source by means of class characteristics with known frequency in the relevant population and individual characteristics. (eg. Rhesus factor). • 4. Association: Determination of contact between two subjects (fibres, glass, human body). • 5. Reconstruction: Determination of facts of the case; nature and place of events in time and space. (as will be presented in court). NEBOH EE (FORENSIC BIOCHEMISTRY)

  11. There are numerous types of bodily fluid that may be found at a crime scene or on a victim, all of which have the potential to be analyzed and used in the identification and incrimination of the perpetrator. The examination of such substances can not only provide clues as to the identity of the offender, but also help investigators develop a detailed picture of the sequence of events which occurred. The presence of certain bodily fluids can be excellent indicators of what has occurred. NEBOH EE (FORENSIC BIOCHEMISTRY)

  12. For example, the presence of semen may suggest a recent sexual encounter, whether consensual or otherwise. Perhaps more obviously, blood at a crime scene is often indicative of some form of physical struggle, assault, or even murder. The analysis of bodily fluids may also determine the presence of quantities of certain substances in the body, such as alcohol or toxins. Bodily fluids can be divided into two categories: excreted fluids and secreted fluids. Excreted fluids that may be found at a crime scene include faeces, vomit, bile, and sebum (skin oil). NEBOH EE (FORENSIC BIOCHEMISTRY)

  13. Secreted fluids include blood, plasma, semen, saliva, female ejaculate, and urine. • When a potential bodily fluid is first discovered at a crime scene, actions may be required to visualize the stain. • Some biological samples are difficult to see with the naked eye, and require particular light or chemical additions to reveal their presence. NEBOH EE (FORENSIC BIOCHEMISTRY)

  14. Presumptive tests may be conducted to give some indication as to the identity of the substance, though these tests are by no means conclusive, and further analysis will be essential. The sample must be then collected and stored appropriately so as to preserve its integrity as best as possible. • Wet samples will often be swabbed, with the swab then being placed in a vial or other airtight container. Individual samples should obviously all be stored separately to prevent contamination. NEBOH EE (FORENSIC BIOCHEMISTRY)

  15. All biological samples are generally dried or frozen during transport and storage. If the samples are to be dried, they should be left to dry by air without the addition of heat, as heat can be damaging to such specimens. • These extensive measures are taken to not only protect the samples for analysis, but also protect the staff handling the samples from biohazards, such as infection from a biological sample. The sample will then be transported to a laboratory so that the analysis can be conducted. NEBOH EE (FORENSIC BIOCHEMISTRY)

  16. The primary goal of this analysis will be to establish exactly what the sample is. Though the answer may seem obvious from the appearance of the sample, conclusive tests should always be conducted. The substance should also be subjected to species-specific tests, as the biological sample may belong to another animal rather than a human. After the completion of such confirmatory tests, DNA analysis may be conducted to attempt to identify the secretor of the sample. NEBOH EE (FORENSIC BIOCHEMISTRY)

  17. COLLECTION OF EVIDENCE NEBOH EE (FORENSIC BIOCHEMISTRY)

  18. COLLECTION OF EVIDENCE NEBOH EE (FORENSIC BIOCHEMISTRY)

  19. COLLECTION OF EVIDENCE NEBOH EE (FORENSIC BIOCHEMISTRY)

  20. EVIDENCE OF SHOE MARKS NEBOH EE (FORENSIC BIOCHEMISTRY)

  21. ANALYSIS WITHOUT CONTAMINATION NEBOH EE (FORENSIC BIOCHEMISTRY)

  22. SOURCES OF DNA IN FORENSICS NEBOH EE (FORENSIC BIOCHEMISTRY)

  23. SECRETORS & NON-SECRETORS • A biological sample may not always contain sufficient DNA to obtain a DNA profile. Individuals may be known as secretors or non-secretors. • Secretors present aspects of their blood’s protein in other bodily fluids, whereas non-secretors will not have sufficient levels of protein in their bodily fluid to establish a match between two samples. Fortunately, the percentage of the population who are non-secretors is comparatively small. NEBOH EE (FORENSIC BIOCHEMISTRY)

  24. BODILY FLUIDS FOUND AT THE CRIME SCENE • Blood One of the most common types of bodily fluid found at crime scenes, particularly the scenes of violent crimes, is blood. Though the appearance of blood is often quite distinct, chemical tests are essential to confirm its identity. Initially presumptive tests are used at the scene, which will merely confirm that the substance in question is most likely blood, though the species is not established at this point. Presumptive blood tests are usually based on the colour change or chemiluminescence of a particular reagent when it comes into contact with the haemoglobin in blood. NEBOH EE (FORENSIC BIOCHEMISTRY)

  25. Luminol is frequently used in initially identifying bloodstains, particularly if the perpetrator has attempted to clean up the blood, thus rendering it invisible to the naked eye. • The presence of blood causes chemiluminescence, the emission of light as a result of a particular chemical reaction, in this case of a blue-green colour. However luminol has been known to react with other substances, including bleach, saliva, and various animal and vegetable proteins. NEBOH EE (FORENSIC BIOCHEMISTRY)

  26. The Kastle-Meyer or phenolphthalein test is another presumptive blood test. The stain in question is collected with a cotton swab before drops of ethanol and phenolphthalein indicator are added. • If no colour change occurs, peroxide is then added. This detects the presence of the enzyme peroxidase in the blood, producing a pink colouring if present. NEBOH EE (FORENSIC BIOCHEMISTRY)

  27. Leucomalachite Green, or LMG, is similar to the Kastle-Meyer test, replacing the phenolphthalein with leucomalachite green. When added to the substance, a green colour will be produced if blood is present. • Hemastixare plastic strips originally used as a form of urine test. In the presence of blood, the strip will take on a green colour. These strips are particularly beneficial in that they are small and easily taken to crime scenes, allowing them to act as a simple, instant presumptive blood test. NEBOH EE (FORENSIC BIOCHEMISTRY)

  28. TEST FOR THE ORIGIN OF BLOOD STAINS It is then necessary to confirm that the blood is of human origin, as animal blood may be completely irrelevant to the crime under investigation. The precipitin test is used to determine the species of the blood’s origin. Blood contains different proteins which vary between species, meaning that the proteins in the blood of one animal may not be accepted by the blood of another species. If a foreign protein is detected, antibodies are produced to protect the body from harm. NEBOH EE (FORENSIC BIOCHEMISTRY)

  29. Serum for this precipitin test is commonly obtained from rabbits, as they have produced antibodies to destroy a small amount of human blood injected into them. • This produced anti-human serum is added to the suspected bloodstain. If the blood is of human origin, the serum will precipitate its proteins, which can be visually observed. NEBOH EE (FORENSIC BIOCHEMISTRY)

  30. COLLECTION OF BLOOD STAINS • Samples of wet bloodstains will usually be collected using a swab, later sealed in an airtight container. Dried bloodstains may be scraped onto a sheet of clean paper or into an appropriate bag. • Any bloodstained items that are collected should be stored separately from one another to avoid contamination and damage to the stains. NEBOH EE (FORENSIC BIOCHEMISTRY)

  31. BLOOD TYPING • Blood typing is one form of categorizing blood, known as the ABO System. A, B, O and AB are the primary blood groups, based on the presence of certain antigens on the surface of the blood cells. Before DNA testing, blood groups were used as a method of eliminating or incriminating suspects, though obviously not exclusively. • Though the use of blood groups cannot specifically identify the individual from whom the blood originated from, they can narrow down the field of search and eliminate particular groups. Rhesus antigens are also commonly studied within the blood typing system. NEBOH EE (FORENSIC BIOCHEMISTRY)

  32. An individual whose cells do possess the Rhesus antigens is known as being RH positive, likewise those without the antigens are known as Rhesus negative. Most people, about 85%, do possess the Rhesus antigens. • The frequencies of certain genes within different blood groups may vary between different races or groups of people, potentially narrowing the field of suspects further. For example, Rhesus antigen V is present in around 40% of West African Negroes, but only 0.5% of Caucasians. NEBOH EE (FORENSIC BIOCHEMISTRY)

  33. The blood type itself may at least suggest the most likely race of the suspect or victim. Type A blood is most common among Europeans, whilst type B is found more commonly among Africans and Asians. • Similarly, type AB is most common amongst those of Japanese origin, and the O type is frequently seen within the Latin American and Native American groups. NEBOH EE (FORENSIC BIOCHEMISTRY)

  34. SALIVA • Saliva is the clear liquid produced in the mouth for various purposes, primarily to act as lubrication for food and provide the enzyme amylase to begin the breakdown of this food. • Composed of water, enzymes, various electrolytes, mucus, and epithelial cells from the inside of the cheeks, it is ideal for DNA profiling. As it contains the same proteins as blood and urine, saliva can also be analyzed to detect the presence of drugs and toxins. NEBOH EE (FORENSIC BIOCHEMISTRY)

  35. COLLECTION OF SALIVA SAMPLES • Collecting a saliva sample from a suspect has become the most common method of collection when carrying out DNA testing and comparison, as it is simpler and far less intrusive than obtaining a blood sample. • A cotton swab is rubbed along the inside of the suspect’s cheek, collecting a sample of saliva and epithelial cells. Saliva will also be of great significance if found at crime scenes, such as on the victim of a sexual assault, on the cigarette end, or around the rim of a glass or bottle. NEBOH EE (FORENSIC BIOCHEMISTRY)

  36. TESTING FOR SALIVA • Due to the high levels of amylase present in saliva, testing for this enzyme is a presumptive test for saliva. • However this enzyme is also found in lower levels in other bodily fluids. Various chromatography and spectroscopy methods are frequently used in the extensive analysis of such samples. NEBOH EE (FORENSIC BIOCHEMISTRY)

  37. SEMEN • Commonly found at the scene of a sexual assault or other sexually-motivated crime, semen plays a crucial role in identifying the perpetrator and linking him to the scene. • Semen is the fluid expelled during male ejaculation, designed to carry and support spermatozoa, the sperm cells. • In a single ejaculate of semen it is estimated that there are on average a quarter of a 250 million sperm cells, making semen ideal for DNA profiling. NEBOH EE (FORENSIC BIOCHEMISTRY)

  38. IDENTIFICATION OF SEMEN • In some cases the fluid may be difficult to see with the naked eye. As previously mentioned, certain alternative light sources can often visualize latent evidence, particularly traces of biological fluids. • Ultraviolet light causes semen to fluoresce, indicating its location whilst not damaging the evidence itself. NEBOH EE (FORENSIC BIOCHEMISTRY) Semen stains on the hand of a victim fluoresces under uv light.

  39. TEST FOR SEMEN • The acid phosphatase test is one of the most common methods used to detect the presence of semen, due to the high levels of the enzyme in human semen. However acid phosphatase is present elsewhere in the body, meaning the test may react positively with other bodily fluids, therefore this should only be used as a presumptive test for semen. • Prostate-Specific Antigen, also known as SPA or p30, is a glycoprotein produced in the prostate gland. This is equally useful in detecting the presence of semen, though is once again only a presumptive test, as PSA is also found in urine. NEBOH EE (FORENSIC BIOCHEMISTRY)

  40. TEST FOR PROSTATE SPECIFIC ANTIGEN NEBOH EE (FORENSIC BIOCHEMISTRY) Testing for semen deposits on the underwear of the victim

  41. The microscopic detection of sperm is a more confirmatory method of discovery. Using microscopic equipment, it is often possible to view the sperm cells, proving their presence. NEBOH EE (FORENSIC BIOCHEMISTRY)

  42. However the older a biological sample is, the further decomposition may have progressed, therefore fresh and well-preserved samples are preferred. • The semen also has a large quantity of citric acid compared to the vaginal fluid which has greater quantity of lactic acid. Hence increased concentration of citric acid in the vaginal fluid which decreases with time is indicative of a post-coital vagina (proving that intercourse took place with or without consent). NEBOH EE (FORENSIC BIOCHEMISTRY)

  43. RAPE CASE NEBOH EE (FORENSIC BIOCHEMISTRY)

  44. RAPE CASE INVESTIGATION • In addition to semen analysis, the examination of the victim should include search for bruises and lacerations in the vagina, as a proof of forceful intercourse. Any sexual encounter with consent is expected not to involve bruises (because there is agreement). • The bodies of the victims should also be examined for bruises on the surface of the body resulting from possible struggle. • Also the victim may have been able to pick up a portion of the culprits skin from scratches. This is a possible source of DNA for analysis. NEBOH EE (FORENSIC BIOCHEMISTRY)

  45. BRUISES FROM STRUGGLE DURING RAPE NEBOH EE (FORENSIC BIOCHEMISTRY)

  46. DATE RAPE CASES • Rape can also be carried out with minimal resistance, whereby the victim’s drink is drugged unsuspecting; • or the victim becomes very drunk with alcohol with the least possible resistance. NEBOH EE (FORENSIC BIOCHEMISTRY)

  47. Rape sometimes precedes murder • When a rape victim is also murdered, the forensic scientist is faced with a double challenge of solving both rape and murder cases. NEBOH EE (FORENSIC BIOCHEMISTRY)

  48. NEBOH EE (FORENSIC BIOCHEMISTRY)

  49. HAIR SAMPLE ANALYSIS • Hair samples are also collected as forensic evidence and unlike bodily fluids, they are easy to handle and analyze. Analysis of hair sample usually becomes very useful in testing for use of illicit drugs, because it gives more useful information concerning drug usage. NEBOH EE (FORENSIC BIOCHEMISTRY)

  50. It usually has a prolonged detection window, making hair analysis suitable for the detection of exposure to illegal drugs for a period of up to 12 months. It also has the advantage of easy sampling and minimal risk of manipulation. Urine analysis, however, reveals only the drug metabolites when the drug has been ingested for a few days and therefore not suitable for hard drug investigation. NEBOH EE (FORENSIC BIOCHEMISTRY)

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