Forensic serology

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Forensic serology

  1. 1. 8-1©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-1©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinChapter 8Chapter 8 Forensic SerologyForensic SerologyCourtesy of C. Fanning
  2. 2. 8-2©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein In 1901, Karl Landsteiner announced one of theIn 1901, Karl Landsteiner announced one of themost significant discoveries of the 20most significant discoveries of the 20ththCentury –Century –the typing of blood – a finding that 29 years laterthe typing of blood – a finding that 29 years laterearned him a Nobel Prize.earned him a Nobel Prize. For years, physicians had attempted to transfuseFor years, physicians had attempted to transfuseblood from one individual to another, but theirblood from one individual to another, but theirefforts often ended in failure because theefforts often ended in failure because thetransfused blood tended to coagulate, or clot in thetransfused blood tended to coagulate, or clot in thebody of the recipient, causing instantaneous death.body of the recipient, causing instantaneous death. Landsteiner was the first to recognize that allLandsteiner was the first to recognize that allhuman blood was not the same; instead, he foundhuman blood was not the same; instead, he foundthat blood is distinguishable by its group or type.that blood is distinguishable by its group or type.HISTORY of SerologyHISTORY of Serology
  3. 3. 8-3©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinKarl Landsteiner (1868-1943)Karl Landsteiner (1868-1943) Out of Landsteiner’s work cameOut of Landsteiner’s work camethe classification system that wethe classification system that wecall the A-B-O system. Nowcall the A-B-O system. Nowphysicians had the key forphysicians had the key forproperly matching the blood ofproperly matching the blood ofa donor to that of a recipient.a donor to that of a recipient.One blood type cannot beOne blood type cannot bemixed with a different bloodmixed with a different bloodtype without disastroustype without disastrousconsequences. This discoveryconsequences. This discoveryhad important implications forhad important implications forblood transfusion and theblood transfusion and themillions of lives it has sincemillions of lives it has sincesaved.saved.
  4. 4. 8-4©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Landsteiner’s findings opened a new field ofLandsteiner’s findings opened a new field ofresearch in the biological sciences. Others began toresearch in the biological sciences. Others began topursue the identification of additional characteristicspursue the identification of additional characteristicsthat could further differentiate blood. By 1937, thethat could further differentiate blood. By 1937, theRh factor in blood had been demonstrated and,Rh factor in blood had been demonstrated and,shortly thereafter, numerous blood factors or groupsshortly thereafter, numerous blood factors or groupswere discovered. More than 100 different bloodwere discovered. More than 100 different bloodfactors have been identified. However, the ones infactors have been identified. However, the ones inthe A-B-O system are still the most important forthe A-B-O system are still the most important forproperly matching a donor and recipient for aproperly matching a donor and recipient for atransfusion.transfusion.Karl LandsteinerKarl Landsteiner
  5. 5. 8-5©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Until the early 1990’s, forensic scientists focusedUntil the early 1990’s, forensic scientists focusedon blood factors, such as A-B-O, as offering theon blood factors, such as A-B-O, as offering thebest means for linking blood to an individual.best means for linking blood to an individual.What made these factors so attractive was that inWhat made these factors so attractive was that intheory, no two individuals, except for identicaltheory, no two individuals, except for identicaltwins, could be expected to have the sametwins, could be expected to have the samecombination of blood factors. In other words,combination of blood factors. In other words,blood factors are controlled genetically an d haveblood factors are controlled genetically an d havethe potential of being highly a highly distinctivethe potential of being highly a highly distinctivefeature for personal identification.feature for personal identification. What makes this observation so relevant is theWhat makes this observation so relevant is thegreat frequency of bloodstains at crime scenes,great frequency of bloodstains at crime scenes,especially crimes of the most serious nature:especially crimes of the most serious nature:homicides, assaults, and rapes.homicides, assaults, and rapes.Application to ForensicsApplication to Forensics
  6. 6. 8-6©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein The advent of DNA technology has dramaticallyThe advent of DNA technology has dramaticallyaltered the approach of forensic scientists towardaltered the approach of forensic scientists towardindividualization of bloodstains and otherindividualization of bloodstains and otherbiological evidence. The search for geneticallybiological evidence. The search for geneticallycontrolled blood factors in bloodstains has beencontrolled blood factors in bloodstains has beenabandoned in favor of characterizing biologicalabandoned in favor of characterizing biologicalevidence by select regions of our deoxyribonucleicevidence by select regions of our deoxyribonucleicacid (DNA), which carries the body’s geneticacid (DNA), which carries the body’s geneticinformation. As a result, the individualization ofinformation. As a result, the individualization ofdried blood and other biological evidence becomedried blood and other biological evidence becomea reality and has significantly altered the role thata reality and has significantly altered the role thatcrime laboratories play in criminal investigation.crime laboratories play in criminal investigation.Application to ForensicsApplication to Forensics
  7. 7. 8-7©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-7©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinNature of BloodNature of Blood•The word blood refers to a highly complex mixture of cells, enzymes,proteins, and inorganic substances.•Plasma, which is the fluid portion of blood, is composed principally ofwater. The plasma accounts for 55% of blood content.•Red blood cells (erythrocytes), white blood cells (leukocytes), andplatelets (thrombocytes) are the solid materials suspended inplasma.•Blood clots when fibrin traps and enmeshes the red blood cells. Ifthe clotted material where removed, a pale yellowish liquid known asserum would be left.•Antigens, usually proteins, are located on the surface of red bloodcells and are responsible for blood-type characteristics.
  8. 8. 8-8©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-8©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinAntigens and AntibodiesAntigens and Antibodies• Red blood cells transport oxygen from the lungs to thegody tissues and remove carbon dioxide from tissues bytransporting it back to the lungs, where it is exhales. Forreasons unrelated to the red blood cell’s transportingmission, on the surface of each cell are millions ofcharacteristic chemical structures called antigens. Morethan 15 blood antigen systems have been identified, but theA-B-O and Rh systems are the most important.•An individual that is type A has A antigens on his/her redblood cells, type B has B antigens, AB has both A and Bantigens, and type O has neither A nor B antigens.Cont.
  9. 9. 8-9©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Another important blood antigen hasAnother important blood antigen hasbeen designated as thebeen designated as the Rh factorRh factor,, or Dor Dantigen. People with the D antigen areantigen. People with the D antigen aresaid to besaid to be Rh positiveRh positive; those without this; those without thisantigen areantigen are Rh negativeRh negative.. In routine blood banking, the presence orIn routine blood banking, the presence orabsence of the three antigens - A, B, andabsence of the three antigens - A, B, andD - must be determined in testingD - must be determined in testingcompatibility of the donor and recipient.compatibility of the donor and recipient.Antigens and AntibodiesAntigens and Antibodies
  10. 10. 8-10©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-10©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinBlood TypingBlood Typing•Serum is important because it contains proteins known asantibodies. The fundamental principal of blood typing is that forevery antigen, there exists a specific antibody. Each antibodysymbol contains the prefix anti-, followed by the name of the antigenfor which is it specific.•The serum-containing antibody is referred to as the antiserum,meaning a serum that reacts against something (antigens).•Antibodies are normally bivalent – that is, they have two reactivesites. This means that each antibody can simultaneously beattached to antigens located on two different red blood cells. Thiscreates a vast network of cross-linked cells usually seen asclumping or agglutination.
  11. 11. 8-11©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-11©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinSerologySerology•The term serology is used to describe a broad scope oflaboratory tests that use specific antigen and serum antibodyreactions.•The identity of each of the four A-B-O blood groups can beestablished by testing the blood with anti-A and anti-B sera.
  12. 12. 8-12©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-12©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinSerology Antigen-Antibody ReactionSerology Antigen-Antibody Reaction•The concept of specific antigen–antibody reactions hasbeen applied to immunoassay techniques for the detectionof drugs of abuse in blood and urine.Red blood cells containing Aantigens do not combine with Bantibodies.Red blood cells containing Bantigens are agglutinated orclumped together in the presenceof B antibodies.
  13. 13. 8-13©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Let’s look a little more closely at this phenomenon. InLet’s look a little more closely at this phenomenon. Innormal blood, antigens on red blood cells andnormal blood, antigens on red blood cells andantibodies coexist without destroying each otherantibodies coexist without destroying each otherbecause the antibodies present are not specific towardbecause the antibodies present are not specific towardany of the antigens. However, suppose a foreign serumany of the antigens. However, suppose a foreign serumadded to the blood introduces a new antibody. Thisadded to the blood introduces a new antibody. Thisresults in a specific antigen-antibody reaction thatresults in a specific antigen-antibody reaction thatimmediately causes the red blood cells to link together,immediately causes the red blood cells to link together,or agglutinate.or agglutinate.Serology Antigen-Antibody ReactionSerology Antigen-Antibody Reaction
  14. 14. 8-14©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Nature has taken this situation into account,Nature has taken this situation into account,because when we examine the serum of typebecause when we examine the serum of typeA blood, we find anti-B and no anti-A.A blood, we find anti-B and no anti-A.Similarly, type B blood contains only anti-A,Similarly, type B blood contains only anti-A,type O blood contains both anti-A and anti-B,type O blood contains both anti-A and anti-B,and type AB blood contains neither anti-A orand type AB blood contains neither anti-A oranti-B. The antigen and antibodyanti-B. The antigen and antibodycomponents of normal blood are summarizedcomponents of normal blood are summarizedin the table given to you in your lab….in the table given to you in your lab…. Lab #1: Training Lab: Blood TypesLab #1: Training Lab: Blood TypesSerology Antigen-Antibody ReactionSerology Antigen-Antibody Reaction
  15. 15. 8-15©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Serology involves a broad scope of laboratory tests thatSerology involves a broad scope of laboratory tests thatuse specific antigen and serum antibody reactions.use specific antigen and serum antibody reactions. An antibody reacts or agglutinates only with its specificAn antibody reacts or agglutinates only with its specificantigen. The concept of specific antigen-antibodyantigen. The concept of specific antigen-antibodyreactions has been applied to techniques for detectingreactions has been applied to techniques for detectingabused drugs in blood and urine.abused drugs in blood and urine. Every red blood cell contains either an A antigen, a BEvery red blood cell contains either an A antigen, a Bantigen, or no antigens. The type of antigen on one’s redantigen, or no antigens. The type of antigen on one’s redblood cells determines one’s ABO blood type. Peopleblood cells determines one’s ABO blood type. Peoplewith type A blood have A antigens on their red bloodwith type A blood have A antigens on their red bloodcells, those with type B blood have B antigens, and thosecells, those with type B blood have B antigens, and thosewith type O blood have no antigens on their red bloodwith type O blood have no antigens on their red bloodcells.cells.Quick ReviewQuick Review
  16. 16. 8-16©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein{{ Radioimmunoassay and EMITRadioimmunoassay and EMITImmunoassayImmunoassayTechniquesTechniques
  17. 17. 8-17©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein The concept of a specific antigen-antibody reaction isThe concept of a specific antigen-antibody reaction isfinding application in other areas unrelated to bloodfinding application in other areas unrelated to bloodtyping. Most significantly, this approach has beentyping. Most significantly, this approach has beenextended to the detection of drugs in blood and urine.extended to the detection of drugs in blood and urine. Antibodies that react with drugs do not existAntibodies that react with drugs do not existnaturally; however, they can be produced in animalsnaturally; however, they can be produced in animalssuch as rabbits by first combining the drug with asuch as rabbits by first combining the drug with aprotein and injecting this combination into the animal.protein and injecting this combination into the animal.This drug-protein complex acts as an antigenThis drug-protein complex acts as an antigenstimulating the animal to produce antibodies.stimulating the animal to produce antibodies.Immunoassay TechniquesImmunoassay Techniques
  18. 18. 8-18©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinDrug Protein Carrierattached to drugInject into rabbitRabbit producesantibodies nearlyspecific to the drug.The recovered blood serum of the animal nowcontains antibodies that are specific or nearlyspecific to the drug originally attached to theprotein carrier.Currently, thousands of individuals regularly submit to urinalysis for thepresence of abused drugs. These individuals include military personnel,transportation industry employees, police and corrections personnel, andsubjects requiring pre-employment drug screening. Immunoassay testing fordrugs has proven quite suitable for handling the large volume of specimensthat must be rapidly analyzed for drug content on a daily basis.
  19. 19. 8-19©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-19©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinImmunoassayImmunoassay•A number of immunological assay techniques are commerciallyavailable for detecting drugs through antigen-antibody reaction.•One such technique, the enzyme-multiplied immunoassaytechnique (EMIT), is used by toxicologists because of its speedand high sensitivity for detecting drugs in urine.•In a typical EMIT analysis, antibodies that will bind to a specificdrug are added to the subject’s urine.•Other immunoassay procedures are also available, such asradioimmunoassay (RIA), which uses drugs labeled withradioactive tags.
  20. 20. 8-20©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein EMIT stands forEMIT stands for enzyme-multipliedenzyme-multipliedimmunoassay techniqueimmunoassay technique. EMIT has. EMIT hasgained widespread popularity amonggained widespread popularity amongtoxicologists because of its speed andtoxicologists because of its speed andhigh sensitivity for detecting drugs inhigh sensitivity for detecting drugs inurine.urine.EMITEMIT
  21. 21. 8-21©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-21©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinAntigen-Antibody ReactionAntigen-Antibody Reaction•When an animal, such as a rabbit or mouse, is injected with anantigen its body will produce a series of different antibodies, allof which are designed to attack some particular site on theantigen of interest.
  22. 22. 8-22©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-22©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinAntigen-Antibody ReactionAntigen-Antibody Reaction•This collection of antibodies is known as polyclonal antibodies.•Alternately, a more uniform and specific collection of antibodiesdesigned to combine with a single antigen site can bemanufactured.•Such antibodies are known as monoclonals.
  23. 23. 8-23©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein{{ Color TestsColor TestsForensicForensicCharacterization ofCharacterization ofBloodstainsBloodstains
  24. 24. 8-24©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-24©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinForensics of BloodForensics of Blood•The criminalist must be prepared to answer the followingquestions when examining dried blood:1. Is it blood?2. From what species did the blood originate?3. If the blood is of human origin, how closely can it beassociated to a particular individual?•The determination of blood is best made by means of apreliminary color test.
  25. 25. 8-25©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-25©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinTesting for BloodTesting for Blood•A positive result from the Kastle-Meyer (phenolphthalein) color testis highly indicative of blood. Hemoglobin causes a deep pink color.•Alternatively, the luminol test is used to search out trace amountsof blood located at crime scenes.•Luminol produces light (luminescence) in a darkened area.Courtesy of C. Fanning Courtesy of C. FanningLuminol withfalse positive(bleach)Courtesy of C. Fanning
  26. 26. 8-26©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein For many years, the most common test was the benzidineFor many years, the most common test was the benzidinecolor test, but because benzidine has been identified as acolor test, but because benzidine has been identified as aknown carcinogen, its use has generally been discontinuedknown carcinogen, its use has generally been discontinuedand replaced with the Kastle-Meyer test.and replaced with the Kastle-Meyer test. Both the benzidine and the Kastle-Meyer color tests areBoth the benzidine and the Kastle-Meyer color tests arebased on the observation that blood hemoglobin possessesbased on the observation that blood hemoglobin possessesperoxidase-like activity. Peroxidases are enzymes thatperoxidase-like activity. Peroxidases are enzymes thataccelerate the oxidation of several classes of organicaccelerate the oxidation of several classes of organiccompounds when combined with peroxides. For example,compounds when combined with peroxides. For example,when a bloodstain, phenolphthalein reagent, and hydrogenwhen a bloodstain, phenolphthalein reagent, and hydrogenperoxide are mixed together, oxidation of the hemoglobin inperoxide are mixed together, oxidation of the hemoglobin inthe blood produces a deep pink color.the blood produces a deep pink color.Benzidine and Kastle-MeyerBenzidine and Kastle-Meyer
  27. 27. 8-27©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein{{Field investigators haveField investigators havefound Hemastix strips afound Hemastix strips auseful presumptive fielduseful presumptive fieldtest for blood. Designed astest for blood. Designed asa urine dipstick test fora urine dipstick test forblood, the strip can beblood, the strip can bemoistened with distilledmoistened with distilledwater and placed in contactwater and placed in contactwith a suspect bloodstain.with a suspect bloodstain.The appearance of a greenThe appearance of a greencolor indicates blood.color indicates blood.HemastixHemastix
  28. 28. 8-28©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein{{Another important presumptiveAnother important presumptiveidentification test for blood is theidentification test for blood is theluminol test. Unlike the benzidineluminol test. Unlike the benzidineand Kastle-Meyer tests, the reactionand Kastle-Meyer tests, the reactionof luminol with blood produces lightof luminol with blood produces lightrather than color. By sprayingrather than color. By sprayingluminol reagent onto a suspect item,luminol reagent onto a suspect item,investigators can quickly screen largeinvestigators can quickly screen largeareas for bloodstains. The sprayedareas for bloodstains. The sprayedobjects must be located in aobjects must be located in adarkened area while being viewed fordarkened area while being viewed forthe emission of light (luminescence);the emission of light (luminescence);any bloodstains produce a faint blueany bloodstains produce a faint blueglow.glow.Luminol and BluestarLuminol and Bluestar
  29. 29. 8-29©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein{{The identification of blood can be madeThe identification of blood can be mademore specific if microcrystalline testsmore specific if microcrystalline testsare performed on the material.are performed on the material.Several tests are available; the twoSeveral tests are available; the twomost popular ones are the Takayamamost popular ones are the Takayamaand Teichmann tests. Both depend onand Teichmann tests. Both depend onthe addition of specific chemicals tothe addition of specific chemicals tothe blood to form characteristicthe blood to form characteristiccrystals containing hemoglobincrystals containing hemoglobinderivatives. Crystal tests are far lessderivatives. Crystal tests are far lesssensitive than color tests for bloodsensitive than color tests for bloodidentification and are more susceptibleidentification and are more susceptibleto interference from contaminants thatto interference from contaminants thatmay be present in the stain.may be present in the stain.Microcrystalline TestMicrocrystalline Test
  30. 30. 8-30©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Once the stain has been characterized as blood, the serologistOnce the stain has been characterized as blood, the serologistdetermines whether the blood is of human or animal origin.determines whether the blood is of human or animal origin.The standard test is the precipitin test. Precipitin tests are basedThe standard test is the precipitin test. Precipitin tests are basedon the fact that when animals (usually rabbits) are injected withon the fact that when animals (usually rabbits) are injected withhuman blood, antibodies form that react with the invadinghuman blood, antibodies form that react with the invadinghuman blood to neutralize its presence. The investigator canhuman blood to neutralize its presence. The investigator canrecover these antibodies by bleeding the animal and isolatingrecover these antibodies by bleeding the animal and isolatingthe blood serum, which contains antibodies that specificallythe blood serum, which contains antibodies that specificallyreact with human antigens. For this reason, the serum is knownreact with human antigens. For this reason, the serum is knownas human antiserum. In the same manner, by injecting rabbitsas human antiserum. In the same manner, by injecting rabbitswith the blood of other known animals, virtually any kind ofwith the blood of other known animals, virtually any kind ofanimal antiserum can be produced. Antiserums areanimal antiserum can be produced. Antiserums arecommercially available for humans for human s and for acommercially available for humans for human s and for avariety of commonly encountered animals – for example, dogs,variety of commonly encountered animals – for example, dogs,cats, chickens and deer.cats, chickens and deer.Precipitin TestPrecipitin Test
  31. 31. 8-31©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinPrecipitin TestPrecipitin Test Several techniques have beenSeveral techniques have beendevised for performingdevised for performingprecipitin tests on bloodstains.precipitin tests on bloodstains.The classic method is to layerThe classic method is to layeran extract of the bloodstain onan extract of the bloodstain ontop of the human antiserum intop of the human antiserum ina capillary tube. Human blood,a capillary tube. Human blood,or for that matter, any proteinor for that matter, any proteinof human origin in the extract,of human origin in the extract,reacts specifically withreacts specifically withantibodies present in theantibodies present in theantiserum, and indicated by theantiserum, and indicated by theformation of a cloudy ring orformation of a cloudy ring orband at the interface of the twoband at the interface of the twoliquids.liquids.
  32. 32. 8-32©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Another method, calledAnother method, called gel diffusion,gel diffusion, takes advantagetakes advantageof the fact that antibodies and antigens diffuse orof the fact that antibodies and antigens diffuse ormove toward one another on a plate coated with amove toward one another on a plate coated with agel medium from a natural polymer called agar.gel medium from a natural polymer called agar.The extracted bloodstain and the human antiserumThe extracted bloodstain and the human antiserumare placed in separate holes opposite each other onare placed in separate holes opposite each other onthe gel. If the blood is human, a line of precipitationthe gel. If the blood is human, a line of precipitationforms where the antigens and antibodies meet.forms where the antigens and antibodies meet.Gel DiffusionGel Diffusion
  33. 33. 8-33©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinGel DiffusionGel Diffusion Similarly, the antigens andSimilarly, the antigens andantibodies can be induced toantibodies can be induced tomove toward one anothermove toward one anotherunder the influence of anunder the influence of anelectrical field. In theelectrical field. In theelectrophoretic method, anelectrophoretic method, anelectrical potential is applied toelectrical potential is applied tothe gel medium; a specificthe gel medium; a specificantigen-antibody reaction isantigen-antibody reaction isdenoted by a line of precitationdenoted by a line of precitationformed between the holeformed between the holecontaining the blood extractcontaining the blood extractand the hole containing theand the hole containing thehuman antiserum.human antiserum.
  34. 34. 8-34©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein 8-34©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinThe precipitin test is very sensitive and requires only a smallamount of blood for testing. Human bloodstains dried for 10– 15 years and longer may still give a positive precipitinreaction. Even extracts of tissue from mummies four to fivethousand years old have given positive reactions with thistest. Furthermore, human bloodstains diluted by washing inwater and left with only a faint color may still yield a positiveprecipitin reaction.
  35. 35. 8-35©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein Once it has been determined that the bloodstainOnce it has been determined that the bloodstainis human, an effort must be made to associate oris human, an effort must be made to associate ordisassociate the stain with a particulardisassociate the stain with a particularindividual. Until the mid-1990’s, routineindividual. Until the mid-1990’s, routinecharacterization of bloodstains included thecharacterization of bloodstains included thedetermination of A-B-O types; however, thedetermination of A-B-O types; however, thewidespread use of DNA profiling or typing haswidespread use of DNA profiling or typing hasrelegated this subject to one of historical interestrelegated this subject to one of historical interestonly.only.Precipitin TestPrecipitin Test
  36. 36. 8-36©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein• The precipitin test uses antisera normally derived fromThe precipitin test uses antisera normally derived fromrabbits that have been injected with the blood of a knownrabbits that have been injected with the blood of a knownanimal to determine the species origin of a questionedanimal to determine the species origin of a questionedbloodstain.bloodstain.• Once it has been determined that the bloodstain is ofOnce it has been determined that the bloodstain is ofhuman origin, an effort must be made to associate orhuman origin, an effort must be made to associate ordissociate the stain with a particular individual.dissociate the stain with a particular individual.• DNA analysis has allowed forensic scientists to associateDNA analysis has allowed forensic scientists to associateblood to a single individual.blood to a single individual.Recap
  37. 37. 8-37©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein• Prior to the advent of DNA typing, bloodstains werePrior to the advent of DNA typing, bloodstains werelinked to a source by A-B-O typing and thelinked to a source by A-B-O typing and thecharacterization of polymorphic blood enzymes andcharacterization of polymorphic blood enzymes andproteins.proteins.• This approach has now been supplanted by the newerThis approach has now been supplanted by the newerDNA technology.DNA technology.• DNA analysis has allowed forensic scientists to associateDNA analysis has allowed forensic scientists to associateblood and semen stains to a single individual.blood and semen stains to a single individual.A-B-O vs. DNA
  38. 38. 8-38©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein• The transmission of hereditary material is accomplished byThe transmission of hereditary material is accomplished bymeans of microscopic units called genes, located onmeans of microscopic units called genes, located onchromosomes.chromosomes.• Alternative forms of genes that influence a givenAlternative forms of genes that influence a givencharacteristic (such as eye color or blood type) are known ascharacteristic (such as eye color or blood type) are known asalleles.alleles.• Paternity testing has historically involved the A-B-O bloodPaternity testing has historically involved the A-B-O bloodtyping system, along with blood factors other than A-B-O.typing system, along with blood factors other than A-B-O.• Currently, paternity testing has implemented DNA testCurrently, paternity testing has implemented DNA testprocedures that can raise the odds of establishing paternityprocedures that can raise the odds of establishing paternitybeyond 99 percent.beyond 99 percent.Heredity and PaternityHeredity and Paternity
  39. 39. 8-39©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein• Many of the cases sent to a forensic laboratoryMany of the cases sent to a forensic laboratoryinvolve sexual offenses, making it necessary toinvolve sexual offenses, making it necessary toexamine exhibits for the presence of seminal stains.examine exhibits for the presence of seminal stains.• The best way to locate and at the same timeThe best way to locate and at the same timecharacterize a seminal stain is to perform the acidcharacterize a seminal stain is to perform the acidphosphatase (an enzyme secreted into seminal fluid)phosphatase (an enzyme secreted into seminal fluid)color test.color test. A purple color indicates acid phosphataseA purple color indicates acid phosphataseenzyme.enzyme.Testing for Seminal StainsTesting for Seminal Stains
  40. 40. 8-40©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard SafersteinTesting for Seminal StainsTesting for Seminal StainsSemen can be unequivocally identified by either the presenceof spermatozoa or of p30, a protein unique to seminalplasma.Forensic scientists can successfully link seminal material toan individual by DNA typing.
  41. 41. 8-41©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein• The rape victim must undergo a medical examination asThe rape victim must undergo a medical examination assoon as possible after the assault.soon as possible after the assault.• At that time the appropriate items of physical evidenceAt that time the appropriate items of physical evidenceincluding clothing, hairs, and vaginal and rectal swabsincluding clothing, hairs, and vaginal and rectal swabscan be collected for subsequent laboratory examination.can be collected for subsequent laboratory examination.• All outer and undergarments should be carefullyAll outer and undergarments should be carefullyremoved and packaged separately in paper (not plastic)removed and packaged separately in paper (not plastic)bags.bags.• Bedding, or the object upon which the assault took place,Bedding, or the object upon which the assault took place,may also be carefully collected.may also be carefully collected.Rape EvidenceRape Evidence
  42. 42. 8-42©2011, 2008 Pearson Education, Inc.Upper Saddle River, NJ 07458FORENSIC SCIENCE: An Introduction, 2nded.By Richard Saferstein• If a suspect is apprehended within 24 hours of the assault,If a suspect is apprehended within 24 hours of the assault,it may be possible to detect the victim’s DNA on theit may be possible to detect the victim’s DNA on themale’s underwear or on a penile swab of the suspect.male’s underwear or on a penile swab of the suspect.• Items routinely collected from the suspect include allItems routinely collected from the suspect include allclothing, pubic hair, head hair, penile swab, and a bloodclothing, pubic hair, head hair, penile swab, and a bloodsample or buccal swab for DNA typing.sample or buccal swab for DNA typing.• The forceful physical contact between victim and assailantThe forceful physical contact between victim and assailantmay result in a transfer of such physical evidence ofmay result in a transfer of such physical evidence ofblood, semen, saliva, hairs, and fibers.blood, semen, saliva, hairs, and fibers.Rape EvidenceRape Evidence

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