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WHAT IS IT?. Forensic Serology. Serology - is the scientific study of blood serum . Purposes: Medical or Forensic Blood samples can change the entire case

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what is it

Forensic Serology

Serology - is the scientific study of

blood serum.

  • Purposes: Medical or Forensic
  • Blood samples can change the entire case
  • 1930, Karl Landsteiner received a Noble Prize award for his research in serology. He introduced to the scientific world that all human blood can be grouped into 4 types known as O, A, B, AB.

Forensic Serology

Serological tests may be performed for diagnostic purposes when an infection is suspected, in rheumatic illnesses, and in many other situations, such as checking an individual's blood type

Diagnostic ID of antibodies in the serum.

  • Antibodies are formed in response to an infection (against a given microorganism)
  • Against other foreign proteins (in response, for example, to a mismatched blood transfusion)
  • One's own proteins (in instances of autoimmunedisease).

Forensic Serology

  • Serology techniques vary depending on the antibodies being studied. Some are: ELISA, agglutination, precipitation, complement-fixation, and fluorescent antibodies.
  • Serological tests are not limited to blood serum, but can also be performed on other bodily fluids such as semen & saliva, which have similar properties to serum.
  • Serological tests may also be used forensically, generally to link a perpetrator to a piece of evidence (e.g., linking a rapist to a semen sample).

Forensic Serology

  • Wet Blood vs. Dried Blood
  • Blood found in different forms
  • Refrigerated red blood cells and serum from white blood cells
  • Where DNA can be taken from
  • Blood pattern analysis helps in the reconstruction of many crime scenes

The Crime Sceneand Blood

forensics of blood
Forensics of Blood

The criminalist needs to answer the following questions when examining dried blood:

  • Is it blood?
  • From what species did the blood originate?
  • If the blood is of human origin, how closely can it be associated to a particular individual?

The determination of blood is best made by means of a preliminary color test.

blood hemo
Blood (HEMO)
  • Blood: water, white blood cells(leukocytes), red blood cells (erythrocytes), various platelets(last component of blood), various proteins, plasma.
  • Red blood cell : RBCs, Carry oxygen to organs of the body, O2.
  • White blood cells: WBCs, part of the Immune system, protects your body from infection and diseases
blood hemo1
Blood (HEMO)
  • The cellular fraction of blood contains red blood cells (erythrocytes) and white blood cells (leucocytes)
  • White blood cells (WBC) are
  • the source of DNA for DNA
  • typing analysis
  • Red blood cells (RBC) do not contain any nuclear DNA



plasma cells
Plasma cells
  • Plasma: primary component (55%) in blood, it has two component:
    • Serum- yellow liquid, contains specific antibody
    • Clotting Proteins
blood and body fluid individuality traditional approaches
Blood and Body Fluid Individuality: Traditional Approaches

1. The Classical or Conventional Genetic Markers:

    • blood groups
    • isoenzymes
    • plasma (serum) proteins
    • hemoglobin variants
    • HLA
  • The first blood group markers were ABO, discovered in 1901 by Karl Landsteiner
blood and body fluid individuality traditional approaches1
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
blood and body fluid individuality traditional approaches2
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
blood and body fluid individuality traditional approaches3
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
blood and body fluid individuality traditional approaches4
Blood and Body Fluid Individuality: Traditional Approaches
  • 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
antibodies and antigens
Antibodies and Antigens

Antibody: Proteins that destroy or inactivate a specific antigen and are found in serum.

Antigen: Substances that stimulates the proteins to produce

antibodies against it.

a b o vs dna
A-B-O vs DNA
  • Prior to the advent of DNA typing, bloodstains were linked to a source by A-B-O typing and the characterization of polymorphic blood enzymes and proteins.
  • This approach has now been supplanted by the newer DNA technology.
  • DNA analysis has allowed forensic scientists to associate blood and semen stains to a single individual.
preserving evidence at the crime scene
Preserving Evidence at the Crime Scene

Forensic Serology

  • Blood evidence results if prepared and collected right
  • Communication from beginning of crime scene to court
  • Videotaping Blood Evidence
  • What Type of Film to use and at medium range
  • Chain of Custody

Forensic Serology

  • A term which describes laboratory tests which employ a specific antigen/antibody reactions. The science dealing with serums and especially their reactions and properties.
  • It includes blood splatter patterns that leads to crime-scene analysis and eventually to a criminal.
  • Every species has a unique type of blood.
forensic identification of blood
Forensic Identification of Blood

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
forensic identification of blood1
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
forensic identification of blood2
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
species determination
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
species determination1
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
forensic nature of blood stains

Forensic Nature of Blood Stains

Blood is the most common and most important evidence in the world of criminal justice.

general bloodstain features
General Bloodstain Features
  • Bloodstain patterns deposited on floors, walls, bedding, and other relevant objects can provide valuable insights into events that occurred during the commission of a violent crime.
  • The crime scene investigator must remember that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding.
general bloodstain features1
General Bloodstain Features

The information one can uncover as a result of bloodstain pattern interpretation includes:

  • The direction from which blood originated
  • The angle at which a blood droplet struck a surface
  • The location or position of a victim at the time a bloody wound was inflicted
  • The movement of a bleeding individual at the crime scene
  • The approximate number of blows that struck a bleeding victim
  • The approximate location of an individual delivering blows that produced a bloodstain pattern
the tests
The Tests
  • A positive result from the KASTLE-MEYER color test is highly indicative of blood.
    • A presumed blood sample is first collected with a swab.
    • A drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxideis applied to the swab.
    • Hemoglobin causes a deep pink color. If the swab turns pink rapidly, it is said to test presumptive positive for blood.
    • Waiting for periods over 30 seconds will result in most swabs turning pink naturally as they oxidize on their own in the air.
the tests1
The Tests
  • The LUMINOL TEST is used to search out trace amounts of blood located at crime scenes.
  • Produces light (luminescence) in a darkened area. To exhibit its luminescence, the luminol must first be activated with an oxidant (H2O2) . Usually, a solution of hydrogen peroxide (H2O2) and a hydroxide (OH-) salt in water is used as the activator. In the presence of a catalyst such as an iron compound (Heme-in blood), peroxide is decomposed to form oxygen and water: 2 H2O2 → O2 + 2 H2O
  • In the forensic detection of blood, the catalyst is the iron present in hemoglobin. Enzymes in a variety of biological systems may also catalyze the decomposition of hydrogen peroxide.
  • BlueStar™ TEST- Comm. Test avail. – doesn’t need total darkness to observe in the field
the tests2
The Tests
  • Precipitin Test – simple test to determine if blood is of human or animal origin. (When animals are injected with human blood, antibodies form reacting with the human blood forming a precipitin band.
  • Microcrystalline tests, such as the Takayama and Teichmann tests, depend on the addition of specific chemicals to the blood so that characteristic crystals will be formed. It is a less sensitive test for blood ID.
  • Once it has been determined that the bloodstain is of human origin, an effort must be made to associate or dissociate the stain with a particular individual.

Blood Stain Pattern Analysis

  • What mechanism creates stains
  • What direction a droplet of blood was traveling
  • Type of object used in attack
  • Position of victim, suspect, and objects
  • Combination of physics, hydraulics, and common sense
  • Helps to reconstruct crime scene and identify criminals
  • Draws from the sciences of biology, chemistry, math, and physics
blood spatter
Blood Spatter
  • Blood Spatter is called Bloodstain Pattern Interpretation.
  • It involves reconstructing the events that must have happened to produce the bleeding.
  • It is not something that most law enforcement officials can do--it usually requires a specialist.

Blood Spatter

Herbert L. MacDonell published a study in 1971; gave tips to investigators:

  • To determine the impact angle of blood on a flat surface by measuring the degree of circular distortion of the stain. The more the angle decreases, the more the stain is less circular and more oblong.
  • Surface texture is one of the key components in determining spatter type, it means that the harder the surface is, the less spatter will result.
  • When a droplet of blood hits a surface which is hard as well as smooth, the blood usually breaks apart upon impact. This in turn causes smaller droplets. These droplets will continue to move in the same direction as the original droplet.
effects of surface texture
Effects of Surface Texture
  • Surface texture and the stain’s shape, size, and location must be considered when determining the direction, dropping distance, and angle of impact of a bloodstain.
  • Surface texture is of paramount importance. In general, the harder and less porous the surface, the less spatter results.
directionality and angle of impact
Directionality and Angle of Impact
  • The direction of travel of blood striking an object may be discerned because the pointed end of a bloodstain always faces its direction of travel.
  • The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion. At right angles the blood drop is circular, as the angle decreases, the stain becomes elongated.
  • Mathematically, the angle of impact can be calculated by the equation:

Sin A = Width of blood stain

Length of blood stain

impact bloodstain spatter patterns
Impact Bloodstain Spatter Patterns
  • Impact spatter occurs when an object impacts a source of blood.
  • Forward spatter is projected outward and away from the source.
  • Back spatter, sometimes called blow-back spatter, is projected backward from the source,
classifying impact spatter
Classifying Impact Spatter

Using droplet size to classify impact patterns by velocity gives investigators insight into the general nature of a crime but cannot illuminate the specific events that produced the spatter pattern.

  • Low Velocity Spatter- drops with diameters of 3 mm or more normally produced by minimal force at a speed of less than 5 ft/sec.
  • Medium Velocity Spatter- drops with diameters from 1-3 mm at a speed of 5 to 25 ft/sec.
  • High Velocity Spatter- drops with diameters of less than 1mm at a speed of 100 ft/sec or faster.

1. Determination of Angle of blood

  • The drop on the right fell 42 inches at an angle of 60-degrees on toward smooth cardboard, while the drop on the left fell the same 42 inches and on to the same surface, but at a 10-degree angle.

Flight Characteristics and Stain Patterns of Human Blood, Herbert L. MacDonnell (Washington DC: USGPO,1971), pp. 44,49


Blood Spatter

  • The blood drop at the right struck a plastic wall tile falling again from 42 inches. On the left, the drop fell from the same distance on to a piece of heavy, unusual textured wallpaper.

Flight Characteristics and Stain Patterns of Human Blood, Herbert L. MacDonnell (Washington DC: USGPO,1971), pp. 36,37


Blood Spatter

  • This drop of blood was tested traveling 4ft/sec., on to a hard cardboard surface. It was traveling from right to left at an angle of 56-degrees. Although not clear in the example, MacDonnell's test showed the smaller drops aimed toward the large one.

Flight Characteristics and Stain Patterns of Human Blood, Herbert L. MacDonnell (Washington DC: USGPO, 1971), pg. 39

area of convergence
Area of Convergence
  • The Area of Convergenceis the point on a two-dimensional plane from which the drops in an impact pattern originated.
  • This can be established by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails.
area of origin
Area of Origin
  • The Area of Originof an impact bloodstain pattern is the area in a three-dimensional space from which the blood was projected.
  • This will show the position of the victim or suspect in space when the stain-producing event took place.
  • The string method is commonly used at a crime scene to approximate the position of the area of origin using found angles of impact of individual stains in the pattern.
gunshot spatter
Gunshot Spatter
  • Gunshot spatter is characterized by fine forward spatter from an exit wound and back spatter from an entrance wound. However, the gunshot produces only back spatter if the bullet does not exit the body.
  • Depending upon the distance from the victim that the gun was discharged, some back spatter may strike the gunman and enter the gun muzzle. This is called the drawback effect.
cast off spatter
Cast-off Spatter
  • A Cast-offpattern is created when a blood-covered object flings blood in an arc onto a nearby surface.
  • This kind of pattern commonly produced by a bloody fist or weapon between delivering blows.
  • The features of the cast-off pattern are affected by the size of the object, the amount of blood, and the direction the object was moving.
  • By counting and pairing forward/backward patterns, one may determine the minimum number of blows delivered.
arterial spray spatter
Arterial Spray Spatter
  • Arterial sprayspatter is created when a victim suffers an injury to a main artery or the heart, and the pressure of the continuing pumping of blood causes blood to spurt out of the injured area.
  • The site of the initial injury to the artery can be found where the pattern begins with the biggest spurt. The trail away from this point shows the victim’s movement.
  • The oxygenated blood spurting from the artery tends to be a brighter red color than blood expelled from impact wounds.
expirated blood patterns
Expirated Blood Patterns
  • An Expirated Blood Patternis created by blood that is expelled from the mouth or nose from an internal injury.
  • The presence of bubbles of oxygen in the drying drops or a lighter color as a result of dilution by saliva can differentiate a pattern created by expirated blood.
  • The presence of expirated blood gives an important clue as to the injuries suffered and the events that took place at a crime scene.
void patterns
Void Patterns
  • A void is created when an object blocks the deposition of blood spatter onto a target surface or object and the spatter is deposited onto the object or person instead.
  • The blank space on the surface or object may give a clue as to the size and shape of the missing object or person.
  • Voids may be applicable for establishing the body position of the victim or assailant at the time of the incident.
contact transfer patterns
Contact/Transfer Patterns
  • A Contact or Transfer Patternis created when an object with blood on it touches one that does not have blood on it.
  • Simple transfer patterns are produced when the object makes contact with the surface and is removed without any movement of the object.
contact transfer patterns1
Contact/Transfer Patterns
  • The size and general shape of the object may be seen in a simple transfer.
  • Other transfers may be caused by movement of the bloody object across a surface.
  • Flow patterns are made by drops or large amounts of blood flowing by the pull of gravity.
  • “Active” flows are formed by blood coming from an actively bleeding wound.
  • “Passive” flows originate with blood deposited on a surface such as an arterial spurt.
  • The flow direction may show movements of objects or bodies while the flow was still in progress or after the blood dried.
  • Interruption of a flow pattern may indicate the sequence and passage of time between the flow and its interruption.
  • A pool of blood occurs when blood collects in a level and undisturbed place.
  • Blood that pools on an absorbent surface may be absorbed throughout the surface and diffuse.
  • The approximate drying time of a pool of blood is related to the environmental condition of the scene. By experimentation an analyst may be able to reasonably estimate the drying times of stains of different sizes.
  • The phenomenon of skeletonization occurs when the edges of a stain dry to the surface.
  • This usually occurs within 50 seconds of deposition of droplets, and longer for larger volumes of blood.
  • After this time, if the bloodstain is altered by a contact of wiping motion, the skeletonized perimeter will be left intact.
  • Knowing the skeletonization time, an investigator determine the timing of movement or activity.
trail patterns
Trail Patterns
  • A trailpattern is a series of drops that are separate from other patterns, formed by blood dripping off an object or injury.
  • The stains form a kind of line or path usually made by the suspect after injuring or killing the victim or injuring themselves.
trail patterns1
Trail Patterns
  • The pattern may show movement, lead to a discarded weapon, or provide identification of the suspect by his or her own blood.
  • The shape of the stains in trail patter can help investigators determine the direction and speed at which a person was moving.
documenting bloodstain evidence
Documenting Bloodstain Evidence
  • Investigators should note, study, and photograph each pattern and drop to accurately record the location of specific patterns and to distinguish the stains from which laboratory samples were taken.
  • In photographs specific techniques are used to document bloodstain patterns.
    • The grid methodinvolves setting up a grid of squares of known dimensions over the entire pattern.
    • The perimeter ruler method involves setting up a rectangular border of rulers around the pattern and then placing a small ruler next to each stain.
interpreting bloodstain evidence
Interpreting Bloodstain Evidence
  • Some jurisdictions have a specialist on staff who will decipher patterns either at the scene or from photographs at the lab.
  • However, it is important that all personnel be familiar with patterns to properly record and document them for use in reconstruction.
bloodstain characterization
Bloodstain Characterization
  • Determination of the group and type of blood, blood testing, bloodstain examination are the main functions of the forensic serologist.
  • In many crime labs, there may be no clear distinction between job title and job function.

Evidence of a sexual assault can come in a variety of forms

rape evidence
Rape Evidence
  • The rape victim must undergo a medical examination as soon as possible after the assault.
  • At that time the appropriate items of physical evidence including clothing, hairs, and vaginal and rectal swabs can be collected for subsequent laboratory examination.
  • All outer and undergarments should be carefully removed and packaged separately in paper (not plastic) bags.
  • Bedding, or the object upon which the assault took place, may also be carefully collected.
rape evidence1
Rape Evidence
  • If a suspect is apprehended within 24 hours of the assault, it may be possible to detect the victim’s DNA on the male’s underwear or on a penile swab of the suspect.
  • Items routinely collected from the suspect include all clothing, pubic hair, head hair, penile swab, and a blood sample or buccal swab for DNA typing.
  • The forceful physical contact between victim and assailant may result in a transfer of such physical evidence of blood, semen, saliva, hairs, and fibers.
collection of rape evidence
Collection of Rape Evidence
  • Lack of presence of semen does not rule out a sexual assault.
  • Physical injuries such as bruises, bleeding, or strangle marks can be indicators.
  • As Locard stated with his theory, physical contact may result in a transfer of physical evidence such as hair, fibers, blood, and semen.
  • DNA can be collected from everywhere on the human body including dandruff and fingernails.
  • To protect this kind of evidence it is important to properly remove, package, and store this evidence.
collection of rape evidence1
Collection of Rape Evidence
  • It should be stored separately in paper bags.
  • Even the victim can be wrapped in something like a cloth if they haven’t washed off any potential evidence.
  • The bed or surface on which the assault took place can also be collected as evidence.
  • The collector of the evidence should be wearing latex gloves to avoid contamination of evidence.
  • The rape victim must have a medical examination done as soon as possible with a sexual assault evidence kit.
collection of rape evidence2
Collection of Rape Evidence
  • A thorough examination will consist of collecting the following: Pubic combings, pubic hair reference samples, external genital dry skin areas, vaginal swab, cervix swab, rectal swab (if the situation calls for it), oral swab, head hairs, blood sample, fingernail scrapings, all clothing that was worn, and a urine specimen.
collection of rape evidence3
Collection of Rape Evidence
  • If a suspect is found, they will be tested for the following: all clothing that is believed to have been worn at the time of the assault, pubic hair combings, pulled head and pubic hair reference samples, penile swab within 24 hours of assault, and a blood sample.




forensic characterization of semen
Forensic Characterization of Semen
  • The average male releases 2.5 to 6ML of seminal fluid during an ejaculation. Each milliliter contains 100 million or more sperm.
  • Examinations of articles that contains seminal stains can be broken up into two processes: locating the stain, and proving it’s identity.
  • Often seminal stains are very visible because they exhibit a stiff, crusty appearance. However, one can’t always rely on appearance alone since the stain isn’t always in an obvious area.
forensic characterization of semen1
Forensic Characterization of Semen
  • Acid phosphatase is an enzyme that is secreted by the prostate gland into seminal fluid. Its presence can be easily detected when it comes into contact with a certain acidic solution and put under a UV light.

If the fabric has been washed or contains minimal amounts of semen, visual examination of the article offers little chance of detecting the stain.

The best way to locate and characterize a seminal stain is to perform the acid phosphatase color test.

forensic characterization of semen2
Forensic Characterization of Semen
  • Sometimes sperm can be seen through a microscope, one would think that with the amount of sperm in a milliliter they would be easy to locate but that’s not always the case.
  • They are extremely brittle when dry and disintegrate easily if the stain is washed or when the stain is rubbed against another object which could happen easily.
  • In the event that there is no detectable sperm in a stain, there’s another way to tell that the stain is indeed seminal. They look for a protein called p30 which is unique to seminal plasma.
testing for seminal stains
Testing for Seminal Stains
  • Many of the cases sent to a forensic laboratory involve sexual offenses, making it necessary to examine exhibits for the presence of seminal stains.
  • The best way to locate and at the same time characterize a seminal stain is to perform the acid phosphatase (an enzyme secreted into seminal fluid) color test.
    • A purple color indicates acid phosphatase enzyme.
testing for seminal stains1
Testing for Seminal Stains
  • Semen can be unequivocally identified by either the presence of spermatozoa or of p30, a protein unique to seminal plasma.
  • Forensic scientists can successfully link seminal material to an individual by DNA typing.

Forensic Detection of Semen 

Methods of Testing for Semen/Sperm

  • Acid Phosphatase
    • Acid phosphatase is an enzyme secreted by the prostate gland that is present in large amounts in seminal fluid. It can be found in other biological fluids including vaginal secretions in smaller quantities.
    • The PAP assay is a well-documented presumptive assay for the presence of semen. 
    • Acid phosphatase activity is 50-1000 times greater in human semen than in any other bodily fluid. Since seminal and vaginal acid phosphatase can not be discriminated, the only approach to differentiating semen in vaginal secretion is by quantitative analysis such as PSA or the microscopic inspection for sperm.

Forensic Detection of Semen 

Methods of Testing for Semen/Sperm

  • The advantages of a PSA determination are: · 
    • Prostate-specific antigen (PSA) or p30 is an accepted marker for detecting semen in criminal cases.
    • The PSA test is NOT presumptive like the Acid Phosphatase (AP) Semen Detection Test.
    • The detection of PSA is possible in cases where no spermatozoa can be found (for example vasectomized or azoospermic men. 
    • PSA can be recovered at detectable concentrations in 30 year old semen stains.
    • Semen samples can show positive PSA results even at a dilution factor of 1:200,000.
    • PSA is detectable in post-ejaculate urine and male urine from adult men and can be detected in urine of 11 yr olds.

Forensic Detection of Semen 

Methods of Testing for Semen/Sperm

  • Microscopic Examination for Sperm
  • There are numerous extraneous objects which are like the detached heads and tails of spermatozoa as to mislead even those who are thoroughly experienced in the work. 
  • The generally accepted rule is that no body which simply resembles the head or tail should be considered as serious proof and the search must continue until perfectly formed and entire spermatozoa are recognized. 

Forensic Detection of Semen 

Methods of Testing for Semen/Sperm

  • Microscopic Examination for Sperm

Forensic Characterization of Saliva

  • Consists of more than 99% water
  • pH range = 6.8–7.0
  • Contains salivary amylase (a digestive enzyme)
  • Produced in three main pairs of salivary glands:
  • parotid, submaxillary, sublingual
  • Cleanses mouth and provides lubrication
  • Saliva is always present at the crime scene if there are bit marks on the victim.
  • It can be used to identify an individual through DNA profiling.
blood and physiological fluid evidence evaluation and initial examination
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
how biological evidence analysis has changed because of dna typing
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
collection preservation and packaging of biological evidence
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
collection preservation and packaging of biological evidence1
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
collection preservation and packaging of biological evidence2
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
test controls substratum comparison specimens and contamination issues
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
test controls substratum comparison specimens and contamination issues1
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
test controls substratum comparison specimens and contamination issues2
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
initial examination of and for biological evidence
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
forensic identification of body fluids
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

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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
forensic identification of body fluids2
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
forensic investigation of sexual assault cases
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”)
forensic investigation of sexual assault cases1
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 (The material evidence in a homicide, such as the discovered corpse of a murder victim, showing that a crime has been committed )
  • If semen or other fluids are found, DNA typing is conducted to determine if there is a match to a suspect or an exclusion
forensic investigation of sexual assault cases2
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)
forensic investigation of sexual assault cases3
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
forensic investigation of sexual assault cases4
Forensic Investigation of Sexual Assault Cases

5. Types of Sexual Assault Cases (3)

    • unknown offender (identification cases)
    • known offender (consent cases)
    • 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
forensic investigation of sexual assault cases5
Forensic Investigation of Sexual Assault Cases

6. Drug Facilitated Sexual Assault:

  • Commonly encountered “date rape” drugs:
    • Rohypnol
    • GHB
    • Ketamine
  • Classified as depressants with amnestic effects; often used along with alcohol
  • These types of cases require toxicological analysis of the evidence
general rules to consider macdonnell
General Rules to Consider-MacDonnell
  • The smaller the size of bloodspatters, the greater the energy required to produce them. Low, medium, and high velocity impact spatter may be identified by their respective sizes but exceptions must also one considered.
  • Before a drop of blood can fall, absent any other form of applied energy, gravitational attraction acting on blood must exceed its surface tension.
  • Diameter of a large bloodstain will be of little or not value in estimating the distance a drop of blood has fallen prior to impact.
  • When considering the shape of a bloodstain for use in calculating its angle of impact, only a sharp, well-defined bloodstain should be used for measuring its width and length.
general rules to consider
General Rules to Consider
  • Directionality of a blood drop while in flight is usually obvious from the geometry of its resulting bloodstain. The pointed end indicates the direction of travel prior to impact on a surface. Directionality may also be determined when edge scallops appear on only one side of a bloodstain.
  • Correct interpretation of bloodstain patterns must include consideration of the surface texture of the material upon which the bloodstains have been deposited.
  • Surface tension prevents spattering regardless of the distance a drop of blood has fallen before impacting a smooth, hard surface such as glass.
  • Edge characteristics of a bloodstain have no value in establishing the distance a drop of blood may have fallen prior to impacting a surface unless the nature of the surface texture is considered.
general rules to consider1
General Rules to Consider
  • Conclusions as to the significance of a limited number of bloodstains should only be drawn with reservations and/or qualifications. It should be remembered that a few bloodstains do not a pattern make. There is nothing wrong with admitting that there are insufficient bloodstains available to form an opinion. It is far better not to have an opinion than to have one that is incorrect.
  • When a dozen or more small bloodstains are present in a recognizable pattern, their size may allow a prediction as to the energy that was required to produce them. When the preponderance of individual bloodstain diameters are less than 1mm, they are consistent with having been produced as a result of a high velocity impact. Most often they would result from a shooting.
general rules to consider2
General Rules to Consider
  • When the preponderance of dozens of individual bloodstains are approximately 1mm or more in diameter, they are consistent with having been produced as a result of a medium velocity impact. Most often they would result from a beating or stabbing.
  • The shape of a bloodstain is a function of the angle at which it impacts a surface. Perfectly round bloodstains result from a ninety degree impact. The angle of impact of an elliptical bloodstain may calculated from its length to width ratio.
  • Bloodstains may often be lifted from the surface upon which they have been deposited. The harder and smoother the surface the more likely they may be successfully lifted.
general rules to consider3
General Rules to Consider
  • When measurements and angles are used to establish the orgin or origins in space, not only will the actual origin be somewhere below the point or points of convergence, but it must be remembered that the investigator is determining a spacial volume and not a small pint of origin.
  • Sobriety of the victim will have no significant effect on how bloodstain patterns are produced. A high blood alcohol level is of no concern to the interpretation of bloodstain patterns.
  • When blood is projected upward with sufficient force to strike a ceiling, it will almost always be the result of a gunshot having an upward trajectory. Such a trajectory is more often the result of a suicide rather than it is a homicide.