Serology

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Serology

• The Bodily Fluids

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Your identity shows up in more places than your
drivers license
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Sources of DNA

• Blood
• Semen
• Teeth
• Skin
• Hairs
• Urine
• Bones
• Muscle

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Blood, sweat, tears, semen, saliva, and vaginal
fluids are some of the bodily fluids that are
frequently found at the scene of a crime.

• Investigators can determine a suspects or
  victims identity through a science called
  Serology

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So, lets get the short story fluids out of the
way first.

• Semen fluoresces (glows) when an ultraviolet
  light or laser light shines on a sample.
• Sperm is only found in semen so finding them
  under a microscope is absolute proof that semen
  is present

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Vaginal Fluids

• Vaginal fluid is more difficult to detect than
  semen. Epithelial cells that line the vagina are
  high in glycogen (a starch which is stored within
  the cells).
• Periodic Acid-Schiff (PAS) is a reagent that
  stains glycogen a bright magenta color in the
  presence of vaginal fluid.

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The Glitches

• Not all vaginal epithelial cells contain
  glycogen. Cells from young women who have not
  begun menstruating as well as cells from
  post-menopausal women rarely contain glycogen.
  Many times the test comes back negative even
  though vaginal fluids are present.

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Saliva

• Saliva is another fluid commonly found at crime
  scenes. Saliva can be found from food, a
  cigarette butt, eating utensils, or even from an
  envelope of a threatening letter.

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During sexual assaults semen, saliva and vaginal
fluid are commonly transferred to the victim, the
victims clothing or nearby surfaces.
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Timing is everything

• Finding out when sexual intercourse or rape
  occurred often is critical in forensics and
  courtroom procedures.
• The duration of sperm mobility in living victims
  is from 4-6 hours. In the case of rape-homicide,
  sperm can remain in the vagina of the victim for
  up to two weeks.
• Dried semen stains can remain identifiable and
  useable for DNA analysis for many years even
  after dry cleaning!

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Secretors

• Approximately 80 - 85 of the population are
  secretors meaning they emit proteins of their ABO
  blood type in all bodily fluid, including seminal
  fluid, saliva, and tears. ABO types found in
  these fluids can be used to eliminate a suspect
  in rape, but they cannot accurately identify the
  individual who secreted them.

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This brings us to Blood

• Blood by far is the most common bodily fluid
  left at a crime scene and its the most useful
  because it opens up many avenues of investigation
  for the forensics team to travel down.

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Understanding Blood

• Blood is a mixture of many components.
• The liquid portion of blood is the plasma. It
  contains proteins, enzymes, clotting factors,
  electrolytes and various cells.
• Serum is the yellowish liquid leftover after the
  blood clots.
• Blood cells come in three types
• Leucocytes or white blood cells (WBC)
• Erythrocytes or red blood cells (RBC)
• Platelets or tiny cells involved in blood
  clotting.

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ABO blood grouping system

• According to the ABO blood typing system there
  are four different kinds of blood types A, B, AB
  or O (null).
• Do you know what type you are???

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Antigens Antibodies

• What makes you the type that you are?

Blood group A If you belong to the blood
group A, you have A antigens on the surface of
your red blood cells and B antibodies in your
blood plasma.
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• Blood group B
• If you belong to the blood group B, you have B
  antigens on the surface of your red blood cells
  and A antibodies in your blood plasma. 

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???

• What do you think blood type
• AB looks like?
• Type O?

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• Blood Type AB

• Blood Type O

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What about this Rh stuff?

• Think of the and of a blood type as another
  antigen found on the surface of a RBC. If you
  are positive (Ex A) you have the extra protein.
  If you are negative, you do not have the extra
  protein.

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Fill in the chart with the appropriate terms
Blood Group Antigens Antibodies Can give blood to Can receive blood from.
AB A B None A, B, AB, or O
A A B A or O
B B A B or O
O None A B O
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It can get more complicated
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of US Population
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• OKso what does this have to do with forensic
  science?
• First, if you find blood at a crime scene you
  can eliminate someone from being a suspect with a
  quick blood typing test (DNA fingerprinting is so
  expensive and takes weeks to complete). It may
  not pinpoint someone specific but it is useful.

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Whos Your Daddy???

• A Jerry Springer show in the making.
• Remember Punnett squares from Biology???
• (Cue Say yes)
• A women wants to find out if so-and-so is the
  father of her baby. She wants child support and
  is convinced that he is the true father.

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• She takes him on TV and wildly denies that she
  has been with many other guys only him. The
  baby has blood type A. Mom has blood type AB and
  Dad has blood type B. Can he be the father?
• Remember that the genotype for blood types can
  be either homozygous or heterozygous. So, what
  do you remember?

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• Moms genotype is definitely AB. Dad can be
  homozygous (BB) or he could be heterozygous (BO)
  for blood type B.
• Place the genotypes in the Punnett and figure
  out the possible offspring of this union. Is
  so-and-so the father? Is this conclusive?

A B
B
B
A B
B
O
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Now we get to the crime scene itself

• We see that there has been a crime committed and
  that there appears to be red liquid in the area.
  We need to answer the questions
• Is this blood?
• Is it human blood?
• Whose blood is it?

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Tests to determine whether bloods really blood

• Kastle-Meyer Color Test Phenolphthalein and
  Hydrogen Peroxide Reacts with the heme group of
  hemoglobin and causes a dark pink color to
  appear.
• Hemastix strip A pretreated stick that when in
  contact with the heme group of blood will turn
  the strip blue-green.
• Luminol When sprayed on a questioned area will
  glow even if the area has been covered up or
  washed with bleach.

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Is it human?

• How might we determine if blood is human or some
  other animal?

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• P.S. When collecting blood from a crime scene
  be sure to package the blood after it dries.
  Remember that wet evidence packaged will be
  rendered unusable if mold or bacteria start to
  grow. Blood is vulnerable to Putrefaction
  (decay).

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What is all of that scientificy stuff regarding
DNA and blood?

• DNA fingerprinting, PCR, STR is the way to
  individualize samples. It is very
  incriminating. Dont even bother to deny
  anything if DNA points to you unless you are an
  identical twin!

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In a very, very small nutshell.

• There are two main techniques used for the
  analysis of DNA, restriction fragment length
  polymorphism (RFLP) and polymerase chain reaction
  (PCR). Each takes the most unique parts of DNA,
  creates banded patterns from those sections and
  compares them to others to seek similarities.

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RFLP vs. PCR

• Both tests are expensive but PCR will be even
  more expensive
• RFLP can take up to 2 weeks while PCR can take up
  to a month to receive results

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• RFLPs are great if you have a blood sample the
  size of a quarter but sometimes you dont have
  that much. PCR is so sensitive that you can have
  as little as that which is the size of a head of
  a pin.

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The printout of the RFLP looks like a bunch of
horizontal lines stacked up.
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PCR readouts show alleles and whether the person
is homozygous or heterozygous for that gene.
Its really quite involved so just know that you
will get caught if you leave your DNA around.
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Oh, and there is the other kind of DNA

• There is mitochondrial DNA which not the same as
  the DNA taken from the nucleus.
• Mitochondrial DNA is found in the mitochondria
  (the powerhouses) of the cell. Mitochondrial
  DNA is only handed down from the maternal side of
  the family. Identical copies from the mother are
  passed down to all of the offspring. This means
  that the mDNA is identical among brothers and
  sisters. You can really put a family together by
  comparing mDNA.

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• It also means that mDNA is horrible at
  individualizing people but really great at
  establishing lineage.
• mDNA can stay preserved in bone cells so well
  that you can process mDNA from bones that are
  hundreds of years old.
• You can compare your mDNA to skeletons from the
  1600s to see if they were related.
• Hopefully, your distant ancestors werent
  criminals. Your family inheritance may be in
  question.

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CODIS

• CODIS stands for Combined DNA Index System which
  is a database of DNA fingerprints taken from
  felons and from biological fluids obtained from
  crime scenes such as assaults, rapes and
  homicides. As of 2004, the Connecticut State
  Crime Lab has expanded its facilities and has
  taken responsibility for much of this National
  Data Bank.

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Intro to Serology Homework Questions

1. Which 3 questions would you ask yourself if you
   think you see blood at a crime scene?
2. What are the 3 possible tests to see if it is
   blood?
3. Name one difference between RFLP and PCR.
4. What are the cons of using mDNA?
5. What is CODIS?