Perishable Evidence

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Chapter 4

• Perishable Evidence
• Presented and prepared by the Barracudas

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Types of Perishable Evidence

• Blood, semen, and fingerprints.
• All three of these kinds of evidence are
  considered perishable, and many times they can be
  the direct link to a crime.
• To keep records of all the samples that
  Criminalists have collected, the FBI developed a
  special database.

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C.O.D.I.S.

• Combined DNA Index System
• This database inventories and catalogs all DNA
  samples entered into it.
• This database allows crime labs to take a DNA
  sample found at a crime scene, and run it through
  that database in the hope of getting a hit.

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• If a close match is found, the computer will
  print out a list of the most likely matches.
• This allows Criminalists to narrow down their
  list of suspects, and determine who was really at
  the crime scene.
• In addition to DNA, a database for firearm
  information is also in the process of
  development. This will allow Criminalists around
  the world to share information about guns and
  bullets.

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Ways to Identify Fingerprints

• One way fingerprints are identified is through a
  computerized imaging system.
• The image is scanned into the computer and it
  identifies characteristics that are specific to
  that particular print. This may be through
  certain connection points in the ridges of the
  print.
• Then a list of me most likely owners is printed
  out.
• The print and the possible matches have to be
  reviewed by a specialist before it can be said
  that a match has been found.

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Points That Make a Print Unique
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The Cells Will Tell

• All of our bodies contain many cells and each
  cell contains our DNA in its nucleus.
• We are constantly shedding skin cells and
  epithelial cells.
• Epithelial cells are found in vaginal fluids,
  saliva, fecal matter, and most moist areas of the
  body. This includes the nose, mouth and
  reproductive areas.
• Different dyes are used to identify if the cells
  came from the mouth or other areas of the body.

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Uses of Iodine

• Lugols Test using iodine, you can tell if
  evidence came into contact with the mouth or
  another part of the body because epithelial cells
  from the mouth stain differently then epithelial
  cells from other areas of the body.
• This test however is not absolute.

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Rape Kit

• The kit comes in an envelope.
• The evidence needs to be taken and stored in a
  timely fashion so that it does not change or
  deteriorate.
• It should also be analyzed quickly after it was
  collected and all proper methods and techniques
  should be utilized.
• Doctors and nurses are trained specifically on
  what evidence to collect and how to collect it.

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What is In a Rape Kit?

• Blood sample or cheek cell sample
• Pubic hair combing
• Sample of victims pubic hair for reference.
• Vaginal and rectal swabs.
• Sample of the vaginal wash used to clean the
  victim after evidence was collected.
• Finger nail clippings

• If she says her attacker licked her on the arm,
  they will take a swab of the licked arm and a
  swab of the un-licked arm for reference.
• Her underwear may also be included in the kit
  since they might have semen on them.
• Sometimes there is also a blood sample that a
  toxicology test if suppose to be run on.

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Time, Time, Time

• It is very important that any sexual assault
  victims report the incident immediately following
  the encounter.
• If this is done, evidence that may be contained
  in the body cavities can be collected and saved
  before the body naturally flushes the impurities
  out.
• If the evidence is not collected quickly after
  the incident, it will be lost and recovery of it
  will not be able to occur.

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On The Hunt For Semen

• When doctors are looking for semen they use
  enzymes.
• They use an enzyme called Seminal Acid Phosphate
  to test for semen.
• However, it the test is not conducted right away,
  the semen will be gone in 24 hours.
• The sperm lasts a little longer and can found in
  the body up to 3 days after the encounter.

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Identification Problems

• Sperm cells have a unique shape.
• Things such as yeast, spores, bacteria, and
  pollen can be observed as sperm but they will not
  stain the same as spermatozoa.
• A single drop of semen can contain as many as
  5,000,000 sperm, and an average ejaculation is 50
  of those drops.

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When Did It Happen?

• One important use of the swabs is to get an
  approximate time of when the attack happened.
• As soon as the semen is deposited in the body, it
  mixes with other fluids and the enzyme activity
  decreases.
• When the Criminalists look at the enzyme activity
  they can give a rough time of when the encounter
  happened by the level of activity. If there is a
  low amount of activity that mean the encounter
  happened a while ago. If the level is higher, it
  probably happened more recently.

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Doctors Should Stay Doctors

• Sometimes doctors decide they want to play
  Criminalist and they save a sample of the vaginal
  swab, and try to run tests on it.
• When they do this, sometimes they think they have
  found a sperm and they put that information in
  the rape kit report.
• This information has to be clarified when it gets
  to the lab however because there are other
  substances that may look like a sperm to the
  untrained eye.

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Paperwork in the Kit

• Also included in the kit is a detailed history of
  the patient, and the rape examination form
  competed by the nurse or doctor that did the
  examination.
• The report states further if she cleaned,
  showered or douched after the incident occurred.
  
• A report of the condition of her genitalia is
  also noted and would describe any signs of trauma
  that may have been present.
• In the case of minors, all evidence of semen is
  considered suspicious and will be investigated.

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Tests at the Lab

• Once the kit arrives at the lab a small slice of
  each swab is clipped off and dropped into a small
  glass test tube.
• Next a drop of water is added to the tube.
• Then a portion of that water is placed on a slide
  and left to dry, and another portion of the water
  is tested for blood.
• To the last bit of liquid, they apply a drop of a
  chemical that turns blue when the enzyme in semen
  is present. As soon as that chemical is applied
  they start timing. The quicker the color change,
  the more of the seminal enzyme the area swabbed
  contained.

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More Tests

• A Christmas Tree stain may also be used to
  identify the different types of cells present on
  the swab.
• Any epithelial cells present will look like
  fried eggs and have a red dyed nucleus and a
  green dyed cytoplasm.
• Any sperm that may have been on the sample will
  stain half red and half clear.
• After this test a Lugols iodine stain is
  preformed.

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Spousal Rape is a Hard Case

• Crime labs can not really do spousal rape because
  the hair and prints of both individuals are all
  over the place.
• Stranger rape is easier because they start from
  scratch on determining who the attacker was.

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Protection is Key

• The Criminalists are aware that they are working
  with substances that could possible transmit
  diseases to them. For this reason each
  Criminalists required to get a Hepatitis vaccine.
  
• The other way to best protect themselves is to
  wear gloves, masks, and wash their hands
  frequently.

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Miscellaneous Items That May be In a Rape Kit

• The lab also gets items in a rape kit like
  undeveloped film, audio cassette tapes, and
  Polaroid's.
• It they receive a tampon that the victim was
  wearing at the time of the attack, they will also
  freeze it so they can later test it for traces of
  semen.

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The Kit of the Attacker

• After a suspect in a rape case has been arrested
  they perform and shorter examination and take
  samples from him.
• These samples include blood samples, hair samples
  from his head and pubic region, a pubic hair
  combing, fingernails and a penis swab.
• All the same tests that are preformed on the
  female samples are then conducted on the male
  samples. With the penis swab they will also be
  able to identify any epithelial cells that may
  have come from the vagina of the victim, though
  they may be dead by the time the suspects swab is
  taken.

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The Results

• With all the tests that the Criminalists conduct
  on the victim and the suspect they have a very
  good chance of determining what really happened,
  and even when it happened.
• With theses tests they also shed light on the
  legitimacy of the accounts of the persons
  involved in the investigation.

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