Serology

1. Serology

2. Serology • Blood is the bodily substance most commonly found at the scene of a crime or on a person, clothing, or a weapon potentially associated with a crime. • Discussion of serology into three sections: the principles of forensic serology, the conventional analyses of blood & other body fluids, and DNA testing.

3. Serology Principles • The science that studies the properties & effects of serums such as analysis of blood traces is called serology. • Types of biological evidence: notably blood, semen, saliva, perspiration, and fecal matter. • Tests to identify blood have been known since at least 1875.

4. Serology Principles • It could not be applied to dried blood nor could it distinguish between human blood and that of other mammals. • Most important test of the time was the guaiacum (tree resin) test. Suspected blood placed in water, added guaiacum then hydrogen peroxide. Blue color = blood. Could be used with very tiny amt. of blood - ? Human or other animal though

5. Serology Principles • Breakthrough in identifying human blood came as a development of experiments of Paul Ehrlich that led to establishment of new scientific discipline: immunology. • An “immune” serum against certain toxic substances could be obtained by injecting substance into an animal in small doses. • An antiserum (a serum with antibodies) could subsequently be taken from animal.

6. Serology Principles • If toxin & antiserum were together injected into another healthy animal, toxin would produce no ill effects. (vaccine) • Karl Landsteiner showed serum of certain persons would agglutinate (clump) red blood cells of certain other persons because red blood cells contain antigens or blood-group factors & the blood serum contains antibodies.

7. Serology Principles • Two antigens are A & B and antibodies are anti-A and anti-B. • Persons with antigen A contain anti-B antibodies: Type A blood. Persons with antigen B contain anti-A antibodies: Type B blood. • Persons with both antigens, neither antibody: Type AB blood. No antigens, both antibodies; Type O blood.

8. Serology Principles • 1915: Dr. Leon Lattes, Asst. Researcher at Institute of Forensic Medicine at University of Turin, Italy, developed a procedure to apply ABO testing to bloodstains on cloth & other materials. • He used saline solution to dissolve dried blood from cloth.

9. Serology Principles • 1910, scientists concluded blood groups could be utilized as evidence in paternity suits & in other criminal investigations. • 1985, Alec Jeffreys & colleagues discovered that portions of DNA structure of certain genes are unique to each individual. Termed the process used to isolate & read these genetic markers as “DNA fingerprinting”.

10. Serology Principles • It is now known that ABO antigens are not limited to red blood cells. • Some 80% or more people have their blood-type antigens in most of their body fluids including saliva and perspiration. Such individuals are known as secretors.

11. Serology Conventional Analysis • Excluding hormones, more than 160 antigens, 150 serum proteins & 250 cellular enzymes are recognized. • Although some of the old tests for blood have been greatly improved & some sophisticated new methods have been developed, the standard procedures still largely apply.

12. Serology Conventional Analysis • These include preliminary tests to identify blood (or semen, etc.), followed by tests for species, blood grouping, & other factors. • The goal is to reach or at least approach as closely as possible the individualization of a sample of blood or other biological evidence.

13. Serology Conventional AnalysisPreliminary Tests • First identify a suspect substance as blood before proceeding to more complex tests. • Most tests are for blood enzyme called peroxidase. Some substances can give similar “false positive” reactions such as horseradish. Therefore, preliminary blood tests are called presumptive tests used for screening. If positive, other tests required to identify the substance as blood.

14. Serology Conventional AnalysisPreliminary Tests • Benzidine test was standard preliminary blood indicator but is highly carcinogenic & no longer used. • Phenolphthalein is becoming increasingly used as blood indicator & called Kastle-Meyer color test; very sensitive test. • It is mixed with hydrogen peroxide. Positive reaction gives a deep pink color.

15. Serology Conventional AnalysisPreliminary Tests • Luminol test: develop invisible traces of blood, especially older dried blood stains. • Even smear marks caused by wiping or mopping in attempts to remove blood stains can be “visualized” by using luminol. • Caution: experience needed; glowing is not always blood; actual bloodstains produce areas of luminescence.

16. Serology Conventional AnalysisPreliminary Tests • Stain is preliminarily identified as blood & must be confirmed & determined to be human or animal origin. Precipitin test identifies proteins in blood based on fact animals (typically rabbits) produce anti-bodies as result of injection of human blood. Resulting anti-serum/anti-human serum reacts positively to human blood forming a white cloudy precipitate.

17. Serology Conventional AnalysisPreliminary Tests • Appropriate controls are tested at same time as suspected blood to ensure anti-serum is both accurate & specific. • Once blood is determined to be human, it is then classified as to blood grouping. • Most common groups are A & O which constitute about 39% & 43% respectively of general population.

18. Serology Conventional Analysis • Additionally discovered blood factors permit increased blood characterization (Rh & MN). Some of other blood parts (plasma proteins & enzymes) may be identified by electrophoresis. • Using a number of factors together greatly narrows the frequency that a given blood sample can be expected to occur in a population.

19. Serology Conventional Analysis • Semen may be identified microscopically by presence of sperm. They are very brittle when dry & disintegrate easily with handling or washing. • Preferred method of locating & identifying simultaneously a seminal stain is by the acid phosphatase color test (enzyme secreted by prostate gland). Purple = positive reaction meaning sperm present.

20. Serology Conventional Analysis • Although other substances, notably fungi, contraceptive creams & vaginal secretions, also react positively to the acid phosphatase test. Difference is that none of the other substances usually react as fast as seminal fluid (under 30 seconds). • Other methods are used to confirm identification such as testing for p30 protein.

21. Serology Conventional Analysis • Other biological evidence includes urine, perspiration, saliva, feces, vomitus & vaginal secretions. Except for vaginal secretions, these types of evidence are rarely encountered. • Paternity determination is another type of conventional serological analysis although not usually relevant to a criminal investigation.

22. Serology Conventional Analysis • We use blood-grouping systems with suspected parents & offspring using the human leukocyte antigen (HLA) test rather than ABO system. Leukocyte = white blood cell. • Currently, DNA testing can increase the probability of paternity to more than 99%.

23. Serology DNA Testing • The 1911 discovery of deoxyribonucleic acid (DNA) – the carrier of genetic information – caused scarcely a ripple in medical jurisprudence. • When Alec Jeffreys discovered the individuality of DNA genes with DNA fingerprinting, it revolutionized forensic serology.

24. Serology DNA Testing • On November 21, 1986, legal & forensic history was made when the kitchen porter became the 1st accused murderer to be cleared as a result of DNA fingerprinting. • Like fingerprints, DNA can be used to make a positive identification. Unlike prints, DNA is inherited, so a small segment of the DNA chain will be identical in all blood relations.

25. Serology DNA Testing • One advantage of DNA is that it is found everywhere white blood cells are found. • DNA structure – twisted ladder or spiral staircase called double helix made up of subunits called nucleotides consisting of a sugar (deoxyribose), a phosphate, & 4 kinds of nitrogenous bases: adenine, guanine, cytosine, thymine. A pairs with T, C pairs with G

26. Serology DNA Testing • The microscopic DNA strands are folded into structures called chromosomes & exist in all cells with a nucleus (except red blood cells = lack nuclei). • In addition to body fluids, DNA is present in tissues, hair roots, bone marrow & tooth pulp.

27. Serology DNA Testing • For forensic purposes, there are two basic DNA procedures in use: restriction fragment length polymorphism (RFLP) & polymerase chain reaction (PCR). • Mitochondrial DNA will be discussed later. • RFLP is used more often in forensic work.

28. Serology DNA Testing • Its disadvantages are that it requires a larger sample than PCR, is time-consuming & labor intensive, & utilizes radioactive reagents that require special lab procedures. • Its great advantage is that it can individualize a specimen to a narrow portion of the population – possibly one person in billions.

29. Serology DNA Testing • In contrast, PCR is faster & simpler to use & may be applied to exceedingly tiny samples. • The technique is based on the way DNA strands reproduce themselves in a cell. • With PCR, an enzyme known as DNA polymerase can be directed to duplicate a strand of DNA several million times.

30. Serology DNA Testing • Unfortunately, the results of PCR are less dramatic than RFLP, being discriminatory on the order of one individual in thousands like the potential billions with RFLP. • Another important investigative capability utilizing DNA evidence is now under development by the FBI laboratory.

31. Serology DNA Testing • It is a national computerized network that compiles databases of various states that require sex criminals & sometimes other violent offenders to provide blood for DNA testing & recording. It’s called CODIS = Combined DNA Index System. • CODIS linked a 1991 Miami rape case with a man who had been convicted of sexual assault in Orlando in 1993.

32. Serology DNA Testing • Before CODIS, the police had not even identified a suspect in the case. • Courts have sometimes challenged DNA evidence on specific grounds such as private labs failure to comply with suitable standards & appropriate controls.

33. Serology DNA Testing • However, properly applied DNA testing is widely accepted as admissible under the standards set by Frye or Daubert. • Per Attorney General Janet Reno’s comment: “Our system of criminal justice is best described as a search for the truth. Increasingly, the forensic use of DNA technology is an important ally in that search.”

34. Serology Case StudyThe O.J. Simpson Trial • Read Case Study & Watch A & E Video “Why O.J. Won”. Do video quiz for grade. • Listen to DNA evidence presented disregarding comments by defense, prosecution, evidence omitted by judge that jurors could not hear or see. • You determine – guilty or not guilty. • Remember… DNA doesn’t lie!!!