1. Chapter 9

2. 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

3. 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

4. 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 cellularmaterial

Anticoagulants preventblood clotting yielding ayellow plasma layer and acell fraction that settles tothe bottom of the tube

5. II. Nature of Blood

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

White blood cells are thesource of DNA for DNAtyping analysis

Red blood cells do notcontain any nuclear DNA

6. 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 areoften used in place of liquidblood as the known sample

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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 locatestains

Both presumptive andconfirmatory tests forsemen stains are available

19. 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

20. 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

21. 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)

22. IX. Forensic Investigation of Sexual Assault Cases

2. The Forensic Scientists Role:

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

The forensic scientists 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

23. 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)

24. 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

25. 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

26. 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

*Figure 9.7* 27. 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

*Figure 9.9* 28. 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

*Figure 9.10* 29. 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

30. 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