Forensic Chemistry Chp 1 Blood

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Information about Forensic Chemistry Chp 1 Blood
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Published on February 28, 2008

Author: ralugersyadiloh

Source: authorstream.com

BLOOD AND BLOOD STAINS:  BLOOD AND BLOOD STAINS IMPORTANCE OF THE STUDY OF BLOOD:  IMPORTANCE OF THE STUDY OF BLOOD As circumstantial or corroborative evidence against or in favor of the perpetrator For disputed parentage Determination of the cause of death and the length of time the victim survived the attack. IMPORTANCE OF THE STUDY OF BLOOD:  IMPORTANCE OF THE STUDY OF BLOOD Determination of the direction of escape of the victim or the assailant. Determination of the origin of the flow of blood. Determination of the approximate time the crime was committed. cont… SOME CHARACTERISTICS OF BLOOD::  SOME CHARACTERISTICS OF BLOOD: The circulating tissue of the body 1 cc of blood: 5,000,000 red cells. Man of average size: about 6 quarts of blood Made up of FORMED ELEMENTS {a. RBC (Erythrocytes) b. WBC (Leucocytes) c. PLATELETS (Thrombocytes)} and PLASMA (liquid portion of blood; composing about 65% of the total blood volume) SOME CHARACTERISTICS OF BLOOD::  SOME CHARACTERISTICS OF BLOOD: Serum – a straw-yellowish liquid that can be seen when blood is allowed to clot. cont… PROBLEMS IN THE STUDY OF BLOOD::  PROBLEMS IN THE STUDY OF BLOOD: Where blood has to be searched for. Collection, preservation and transportation of specimen suspected to contain blood. Does the stain contain blood or another substance? PROBLEMS IN THE STUDY OF BLOOD::  PROBLEMS IN THE STUDY OF BLOOD: If the stain is that of blood, is it human or animal? If the stain is of human blood, did it come from the victim, the accused or from other persons? cont… Whether Stain Is of Blood or Another Substance:  Whether Stain Is of Blood or Another Substance Preliminary Test (a.k.a.: Presumptive or Color Test) – a positive result is not conclusive that the stain is blood but a negative result is conclusive that the stain is not blood. REASON: Other substances may yield the same reaction as blood. This includes: sputum, nasal secretion, plant juices, formalin, etc. Whether Stain Is of Blood or Another Substance:  Whether Stain Is of Blood or Another Substance B. Confirmatory Tests – The actual proof that a stain is blood consists in establishing the presence of characteristic blood pigment, hemoglobin or one of its derivatives. The 3 Confirmatory Tests commonly employed are Teichmann, Takayama and Wagenhaar Tests. They are designed to show the presence of hemoglobin in a suspected bloodstain by the appearance of specific crystals observed under a microscope. cont… Preliminary Tests for the Presence of Blood:  Preliminary Tests for the Presence of Blood Preliminary Tests for the Presence of Blood:  Preliminary Tests for the Presence of Blood cont… Preliminary Tests for the Presence of Blood:  Preliminary Tests for the Presence of Blood cont… Preliminary Tests for the Presence of Blood:  Preliminary Tests for the Presence of Blood cont… Preliminary Tests for the Presence of Blood:  Preliminary Tests for the Presence of Blood cont… Confirmatory Tests:  Confirmatory Tests Teichmann or Haemin Crystal Test – Dark brown rhombic crystals arranged singly or in clusters Takayama or Haemochromogen Crystal Test – Large rhombic crystals of salmon-pink color arranged in clusters, sheaves and other forms Confirmatory Tests:  Confirmatory Tests Wagenhaar Test or Acetone-Haematin – Small dark, circular crystals cont… Whether Blood Is of Human or Animal:  Whether Blood Is of Human or Animal Precipitin Test (human antiserum) – The formation of gray precipitation ring at the interface of the two layers within 20 minutes indicates that the stain is human blood. ORIGIN OF BLOOD:  ORIGIN OF BLOOD This is determined by blood grouping. A-B-O system, which was discovered by Karl Landsteiner in early 1900s, was the first system of blood grouping. SUMMARY OF THE COMMON BLOOD GROUP SYSTEM:  SUMMARY OF THE COMMON BLOOD GROUP SYSTEM BLOOD OF DISPUTED PARENTAGE:  BLOOD OF DISPUTED PARENTAGE BLOOD OF DISPUTED PARENTAGE:  BLOOD OF DISPUTED PARENTAGE cont… OTHER BODILY FLUIDS:  OTHER BODILY FLUIDS It has been found that some individuals secrete in their fluids – such as: semen, saliva, urine and vaginal fluids and substances, corresponding to their blood groups. Therefore, it is possible to determine the ABO blood group of suspected stains of body fluids from the secretors. OTHER BODILY FLUIDS:  OTHER BODILY FLUIDS A blood also extracted from individuals suspected to be intoxicated are examined to determine whether they are under the influence of alcohol or not, at the time of the extraction. The percentage of alcohol obtained from the blood are examined and interpreted by the medico-legal officer to determine the percentage of alcohol level in the blood. cont… THE PERISHABLE NATURE OF BLOOD:  THE PERISHABLE NATURE OF BLOOD Blood is type of evidence, which undergoes a rapid change in its character with the passage of time, as the process of clothing and drying commence almost immediately on exposure to air. Furthermore, blood offers little resistance to decomposition, especially when exposed to certain conditions and influences, which if prolonged, will cause the specimen to lose its identity. THE PERISHABLE NATURE OF BLOOD:  THE PERISHABLE NATURE OF BLOOD It is therefore extremely important that blood samples be sent to the laboratory as soon as possible after their discovery or scientifically preserve. Prior to the general search of the crime scene, the floor should be examined carefully in order to minimize the danger of loss or destruction caused by being walked upon by persons otherwise engaged in the investigation. cont… GUIDE TO PHYSICAL EVIDENCE COLLECTION:  GUIDE TO PHYSICAL EVIDENCE COLLECTION Amount Desired Specimen – Liquid Known Samples Standard – One tube each (sterile) 5cc-10cc blood only. No preservatives. Evidence – All Send By – Registered mail or equivalent SPECIMEN – LIQUID KNOWN SAMPLES:  SPECIMEN – LIQUID KNOWN SAMPLES Identification – outside test tube: use adhesive tape. Name of donor, date taken, doctor’s name, investigator’s name or initials. Wrapping and Packing – wrap in cotton/soft paper. Place in mailing tube or suitable strong mailing carton. SPECIMEN – LIQUID KNOWN SAMPLES:  SPECIMEN – LIQUID KNOWN SAMPLES Remarks – submit immediately. Don’t hold awaiting additional items for comparison. Do not freeze, keep refrigerated until mailing. Do no add refrigerants and/or dry ice to sample during transit. Label “Fragile.” cont… GUIDE TO PHYSICAL EVIDENCE COLLECTION:  GUIDE TO PHYSICAL EVIDENCE COLLECTION Amount Desired Specimen – small quantities: a. Liquid Questioned Samples Standard – All Evidence – All Send By – Registered mail or equivalent cont… SPECIMEN – SMALL QUANTITIES: a. Liquid Questioned Samples:  SPECIMEN – SMALL QUANTITIES: a. Liquid Questioned Samples Identification - outside test tube: use adhesive tape. Name of donor, date taken, doctor’s name, investigator’s name or initials. Wrapping and Packing – wrap in cotton/soft paper. Place in mailing tube or suitable strong mailing carton. SPECIMEN – SMALL QUANTITIES: a. Liquid Questioned Samples:  SPECIMEN – SMALL QUANTITIES: a. Liquid Questioned Samples Remarks – If unable to expeditiously furnish sample: Dry on nonporous surface, scrape off or collect (use eye droppers or clean spoon), transfer to nonporous surface or absorb in sterile gauze and let it dry. cont… GUIDE TO PHYSICAL EVIDENCE COLLECTION:  GUIDE TO PHYSICAL EVIDENCE COLLECTION Amount Desired Specimen – Small quantities: b. Dry stains not on fabrics Standard – As much as possible Send By – Registered mail or equivalent cont… SPECIMEN – SMALL QUANTITIES: b. Dry Stains Not On Fabrics:  SPECIMEN – SMALL QUANTITIES: b. Dry Stains Not On Fabrics Identification – Outside pillbox or plastic vial: label with type of specimen, date secured, investigator’s name or initials. Wrapping and Packing – Seal to prevent leakage Remarks – Keep it dry. Do not use envelopes. GUIDE TO PHYSICAL EVIDENCE COLLECTION:  GUIDE TO PHYSICAL EVIDENCE COLLECTION Amount Desired Specimen – Small quantities: a. For toxicological use Standard – Not applicable Evidence – 20 cc of blood and preservative mixture Send By – Registered mail or equivalent cont… SPECIMEN – SMALL QUANTITIES: a. For Toxicological Use:  SPECIMEN – SMALL QUANTITIES: a. For Toxicological Use Identification – outside test tube: use adhesive tape. Name of donor, date taken, doctor’s name, investigator’s name or initials. Wrapping and Packing – Medical examiner should use a standard blood collection kit. Remarks – Preservative desired (identify preservation used). Refrigerate. Can freeze. GUIDE TO PHYSICAL EVIDENCE COLLECTION:  GUIDE TO PHYSICAL EVIDENCE COLLECTION Specimen – 3. Stained clothing, fabric, etc. Standard – Not applicable. Evidence – As found. Send By – Registered mail or equivalent cont… SPECIMEN – 3. Stained clothing, fabric, etc.:  SPECIMEN – 3. Stained clothing, fabric, etc. Identification – Use tag or mark directly on clothes: type of specimens, date secured, investigator’s name or initials. Wrapping and Packing – Wrap each article separately. Label outside package as to contents. Place in strong box to prevent shifting of contents. SPECIMEN – 3. Stained clothing, fabric, etc.:  SPECIMEN – 3. Stained clothing, fabric, etc. Remarks – If wet when found, dry by hanging. DO NOT USE HEAT TO DRY. Avoid direct sunlight while drying. Do not use preservatives. cont…

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