Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological...

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Chapter 9

Transcript of Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological...

Page 1: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

Chapter 9

Page 2: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

Blood and Physiological Fluid Evidence: Evaluation and Initial Examination

• How Biological Evidence Analysis Has Changed Because of DNA Typing

• Nature of Blood

• Collection, Preservation, and Packaging of Biological Evidence

• Test Controls, Substratum Comparison Specimens, and Contamination Issues

• Initial Examination of and for Biological Evidence

• Forensic Identification of Blood

• Species Determination

• Forensic Identification of Body Fluids

• Forensic Investigation of Sexual Assault Cases

• Blood and Body Fluid Individuality: Traditional Approaches

Page 3: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

I. How Biological Evidence Analysis has Changed Because of DNA Typing

• Prior to the introduction of forensic DNA typing analysis, blood groups were the genetic markers that were analyzed from biological evidence (forensic serology)

• Forensic biology now refers to the preliminary examination of biological evidence prior to the DNA typing analysis procedures

Page 4: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

II. Nature of Blood• Blood contains cells, nutrients, chemical messengers, and

ingested substances

• A tube of whole blood will clot producing two fractions: a yellow serum layer and a dark red clot containing cellular material

• Anticoagulants prevent blood clotting yielding a yellow plasma layer and a cell fraction that settles to the bottom of the tube

Page 5: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

II. Nature of Blood

• The cellular fraction of blood contains red blood cells (erythrocytes) and white blood cells (leucocytes)

• White blood cells are the source of DNA for DNA typing analysis

• Red blood cells do not contain any nuclear DNA

Page 6: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

III. Collection, Preservation, and Packaging of Biological Evidence

• Blood or Buccal Swabs from Known Person:

• Blood is drawn into a vacutainer tube containing an anticoagulant such as EDTA (“purple top” tube)

• Buccal (cheek) swabs are often used in place of liquid blood as the known sample

Page 7: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

III. Collection, Preservation, and Packaging of Biological Evidence

Biological Evidence from Scenes:

• Fresh or web blood should be collected on clean, sterile, gauze and allowed to dry

• Four sampling methods for dried blood:– Cutting – For stains on objects that are difficult to submit to the lab. The

cut portion should include unstained areas around the bloodstain

– Swabbing – Stain is transferred to a swab which has been moistened with sterile water or saline.

– Scraping – a sharp instrument is used to scrape the stain off of a surface & onto clean paper

– Elution – using a small amount of saline or distilled water to dissolve the dried stain

Page 8: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

III. Collection, Preservation, and Packaging of Biological Evidence

• The most important consideration for preserving biological evidence from scenes is to thoroughly dry the item before packaging and then store in a cool dry environment

• Biological evidence must be packaged in paper containers that can breathe

Page 9: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IV. Test Controls, Substratum Comparison Specimens, and Contamination Issues

1. Known (Exemplar or Reference) Control:– are specimens from a known source

– essential for comparison with DNA profiles from evidentiary specimens

2. Alibi (Alternative) Known Control:– From a known source that may be the source of the

evidence

3. Blank Control:– A specimen known to be free of the item or substance

being tested

Page 10: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IV. Test Controls, Substratum Comparison Specimens, and Contamination Issues

4. Substratum Comparison Specimens:

• Substratum refers to the underlying material or surface on which the evidence is found

• A substratum comparison specimen is subjected to the same testing as the evidence

• The specimen helps to detect interference in lab tests originating from the evidence surface

• An unstained portion of the evidence underlying material is collected for this purpose

Page 11: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IV. Test Controls, Substratum Comparison Specimens, and Contamination Issues

• Evidence may be contaminated in several ways:– Biological material may have been on a surface before the

biological evidence was deposited

– During scene searching &/or processing activities

– During laboratory examinations &/or manipulations

Page 12: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

V. Initial Examination of and for Biological Evidence

• The initial examination is designed to evaluate stains for possible evidentiary value

• Activities include:– Searching for biological stains

– Preliminary tests for physiological fluids

– Positive preliminary tests are then subjected to confirmatory tests

– Cutting out or transferring stains to swabs for subsequent examinations

Page 13: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VI. Forensic Identification of Blood

Two categories of identification tests:

• Presumptive or preliminary test– Used for screening specimens that might contain the substance or

material of interest

– Both false positive and false negative results may be obtained

• Confirmatory test– Are tests which are entirely specific for the substance or material for

which it is intended

– A positive confirmatory test is interpreted as an unequivocal demonstration that the specimen contains the substance or material

Page 14: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VI. Forensic Identification of Blood

Presumptive Tests for Blood:

• Presumptive blood tests are used to screen evidence for the possible presence of blood

• Most are color tests and are based on the peroxidase-like activity of hemoglobin

• Peroxidase catalyzes the following reaction

• Reduced Dye + peroxide --> Oxidized dye + water

• The presence of hemoglobin catalyzes the reaction, forming a colored dye product

• Positive presumptive tests do not prove that blood is present

Page 15: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VI. Forensic Identification of Blood

Confirmatory Tests for Blood:

• Older tests included crystal tests such as the Teichmann and Takayama tests

• Current immunological tests use antibodies specific for human hemoglobin, thus combining the confirmatory test for blood with a human species test

• The crystal tests and the immunological tests are known as direct confirmatory tests

Page 16: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VII. Species Determination

• Tests must be done on blood specimens to determine the species of origin

• Species origin tests are done using immunological methods which involve the interaction of antigens and antibodies

• Hemoglobin from human red blood cells can be used as the antigen to produce anti-human hemoglobin serum

• Specific antiserum can be used to test for the presence of antigens in unknown specimens

Page 17: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VII. Species Determination• Common immunological species tests include the Ouchterlony

method

• Extracts of the bloodstain to be analyzed are tested with specific antisera

• If the bloodstain contains the antigens corresponding to the specificity of the antiserum, a visible precipitate (precipitin) is obtained

Page 18: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VIII. Forensic Identification of Body Fluids

1. Identification of Semen:• Semen is a mixture of specialized cells, called spermatozoa,

suspended in a fluid known as seminal plasma

• UV light causes semen stains to fluoresce, and is therefore used to locate stains

• Both presumptive and confirmatory tests for semen stains are available

Page 19: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VIII. Forensic Identification of Body Fluids

Presumptive Test for Semen:

• The AP test is a color test based on the detection of acid phosphatase, an enzyme from the prostate gland that is found in high concentration in human semen

Confirmatory Test for Semen:

• A commonly used approach is to use a microscope to detect spermatozoa in smears made from dried stains

• When no sperm are found, immunological methods are used to detect the presence of a prostate gland protein called p30 or PSA

Page 20: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

VIII. Forensic Identification of Body Fluids

2. Identification of Vaginal Secretions, Saliva, and Urine:• There are no reliable methods for identifying human vaginal

material

• Presumptive tests for saliva are based on the presence of the enzyme amylase

• There are no confirmatory tests for saliva

• Presumptive tests for urine are based on the presence of urea and creatinine

• There are no confirmatory tests for urine

Page 21: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IX. Forensic Investigation of Sexual Assault Cases

1. Coordination of Effort – SANEs and SARTs

• The medical examination of complainants in sexual assault cases is performed by specially trained sexual assault nurse examiners (SANE)

• Forensic nurses take a lead role in the coordinated response by the sexual assault response team (SART)

• Complainants are taken to a medical facilities or a SANE/SART facility to attend to their medical needs and to collect relevant evidence using a sexual assault evidence collection kit (”rape kit”)

Page 22: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IX. Forensic Investigation of Sexual Assault Cases

2. The Forensic Scientist’s Role:

• Sexual assault evidence collection kits are forwarded to the forensic lab for examination

• The forensic scientist’s primary role is the analysis of the physical evidence

• If semen is present it helps to establish the corpus delicti

• If semen or other fluids are found, DNA typing is conducted to determine if there is a match to a suspect or an exclusion

Page 23: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IX. Forensic Investigation of Sexual Assault Cases

3. Medical Examination:

• Medical evaluation and treatment of sexual assault victims initially involves recording the history of the events, tending to any injuries, and documenting any injuries, bruises, or contusions

• This is followed by evidence collection, which includes clothing, vaginal swabs, pubic hair combings, any stains on the skin surface, and a known control (blood or buccal swab)

Page 24: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IX. Forensic Investigation of Sexual Assault Cases

4. Sexual Assault Evidence Collection Kits:• Sexual assault evidence collection kits contain a variety of

containers and envelopes plus a detailed set of instructions on how to use them

• Not every container/envelope is used in every case

Page 25: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IX. Forensic Investigation of Sexual Assault Cases

5. Types of Sexual Assault Cases

• There are three types of sexual assault cases: unknown offender (identification cases), known offender (consent cases), and sexual assaults involving children

• DNA profiling is helpful in identification cases but not in consent cases

• State laws define the age of consent, thereby differentiating between an adult and child

Page 26: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

IX. Forensic Investigation of Sexual Assault Cases

6. Drug Facilitated Sexual Assault:

• Several drugs are commonly encountered as “date rape” drugs: rohypnol, GHB, & ketamine

• All are depressants with amnestic effects, and are often used along with alcohol

• These types of cases require toxicological analysis of the evidence

Page 27: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

X. Blood and Body Fluid Individuality: Traditional Approaches

1. The Classical or Conventional Genetic Markers:

• 5 categories of classical genetic markers: blood groups, isoenzymes, plasma (serum) proteins, hemoglobin variants, and HLA

• The first blood group markers were ABO, discovered in 1901 by Karl Landsteiner

Page 28: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

X. Blood and Body Fluid Individuality: Traditional Approaches

• ABO markers were first applied to criminal cases involving bloodstains by Dr. Leon Lattes of Italy in 1913

• Isoenzymes are enzymes which occur in multiple molecular forms, reflecting differences in the gene that code for the enzyme

• Similarly, there are common variants of the protein hemoglobin

Page 29: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

X. Blood and Body Fluid Individuality: Traditional Approaches

2. How Does Typing Genetic Markers Help “Individualize” a Biological Specimen?

• A gene is a region of DNA that codes for a particular protein or enzyme

• Because chromosomes are paired (maternal and paternal), and there is one gene on each chromosome, the genes are paired

• A gene locus is the location on a chromosome where a particular trait is determined

Page 30: Chapter 9. Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing.

X. Blood and Body Fluid Individuality: Traditional Approaches

• The genes making up a pair at a given locus are called alleles

• The alleles may be the same (homozygous) or different (heterozygous)

• Population genetics looks at how often alleles found at a given locus occur in a population

• A portion of a large population is sampled and tested to determine the frequency of a particular allele

• Statistics are used to estimate the frequency of an allele in the entire population