Criminal Investigations

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Criminal Investigations

• Forensics and Physical Evidence
• Chapter 5

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Objectives

• What is involved in processing physical evidence
• How to determine what is evidence
• What a standard of comparison is and how to use
  it
• What common errors in collecting evidence are
• How to identify evidence

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Objectives Cont.

• What to record in your notes
• How to package evidence
• How to convey evidence to a department or a
  laboratory
• What types of evidence are most commonly found
• What can and cannot be determined from
  fingerprints, bloodstains and hairs
• How and where evidence is stored
• How to admit physical evidence in court
• How physical evidence is finally disposed of

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Introduction

• Modern forensic evidence dates back to 1910 where
  the exchange principle is used. A famous French
  criminologist named Edmond Locard stated that a
  criminal always removes something or leaves
  something at a crime scene that is incriminating.
• The primary purpose of an investigation is to
  locate, identify, and preserve evidence. This
  evidence is later used to support a theory or a
  claim about the accused.
• This chapter covers the types of investigative
  equipment available and how to discover,
  recognize, and examine evidence. This is
  followed by discussing frequently discovered
  evidence such as blood, fingerprints, DNA, other
  bodily fluids, fibers, tire marks, etc.

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Definitions

• Physical evidence-is anything real that helps
  establish the facts in a case
• Trace evidence-extremely small items such as hair
  or fibers
• Direct evidence-establishes proof of a fact
  without any other evidence
• Prima facie evidence-evidence established by law
• Circumstantial evidence-evidence that tends to
  incriminate a person

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Definitions Cont.

• Exculpatory evidence-physical evidence that would
  clear one of blame
• Associative evidence-links a suspect with a crime
• Corpus delicti evidence-establishes that a crime
  has been committed
• Corpus delicti-the fact that death resulted from
  a criminal act

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Processing physical evidence

• Includes
• Discovering, reorganizing and examining it,
• Collecting, recording and identifying it,
• Packaging, conveying and storing it, exhibiting
  it in court,
• Disposing of it when the case is closed

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Discovering, Recognizing and Examining Evidence

• To determine what is evidence
• Consider the apparent crime
• Look for any objects unrelated or foreign to the
  scene, unusual in location or number, damaged or
  broken or whose relation to other objects
  suggests a pattern that fits the crime
• A standard of comparison is an object, measure or
  model with which evidence is compared to
  determine whether both came from the same source

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Collecting, Marking and Identifying Evidence

• Common errors in collecting evidence are
• Not collecting enough of the sample
• Not obtaining standards of comparison
• Not maintaining the integrity of the evidence

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Collecting, Marking and Identifying Evidence Cont.

• Mark or identify each item of evidence in a way
  that can be recognized later
• Indicate the date and case number as well as your
  personal identifying mark or initials
• Record in your notes the date and time of
  collection, where the evidence was found and by
  whom, the case number, a description of the item
  and who took custody

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Packaging and Preserving Evidence

• Package each item separately in a durable
  container to maintain the integrity of evidence
• You dont want damage or cross-contamination
• Each piece of evidence has specific requirements
  for packaging.
• Example- Some evidence is sterile containers
  while others may be placed in cotton to prevent
  breakage such as a firing pin.
• Some items should be immediately taken to the
  crime lab for analysis and left there with a
  chain of custody form

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Transporting Evidence

• Personal delivery, registered mail, insured
  parcel post, air express, Federal Express and
  United Parcel Service (UPS) are legal ways to
  transport evidence
• Always specify that the person receiving the
  evidence is to sign for it

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Physical Evidence

• Fingerprints, voiceprints, shoe and tire
  impressions, bite marks, tools and tool marks,
  weapons and ammunition, glass, soils and
  minerals, body fluids (including blood), hairs
  and fibers, sage insulation, rope and tape,
  drugs, documents and laundry and dry-cleaning
  marks

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Fingerprints

• Latent
• Visible
• Plastic
• Invisible
• Any hard, smooth, nonporous surface can contain
  latent fingerprints
• Prints of persons with reason to be at the scene
  are taken and used as elimination prints
• Are a positive evidence of a persons identity

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Evidence

• Cast shoe or tire tread impressions found in
  dirt, sand or snow
• Identify each suspect with a string tag
• Wrap it separately and pack it in a strong box
  for sending to the laboratory
• Photograph tool marks and then either cast them
  or send the object on which they appear to a
  laboratory
• Tool mark is compared with a standard of
  comparison impression rather than with the tool
  itself

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Evidence cont.

• Examine weapons for latent fingerprints,
  photograph and then identify them with a string
  tag, unload guns, record serial number on the
  string tag and in your notes
• Label glass fragments using adhesive tape on each
  piece, wrap each piece separately in cotton to
  avoid chipping and place in a strong box marked
  fragile to send to the laboratory

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Evidence cont.

• Put one pound of comparison soil into a container
  identified on the outside, collect evidence soil
  the same way, seal both containers to prevent
  loss, wrap them and send them to the laboratory
• Put samples of safe insulation in paper
  containers identified on the outside
• Put labeled rope, twine and string into a
  container, put tapes on waxed paper or cellophane
  and then place them in a container

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Evidence cont.

• Put liquid drugs in a bottle and attach a label,
  put powdered and solid drugs in pill or powder
  box and identify in the same way
• Do not touch documents with your bare hands,
  place documents in a cellophane and then in a
  manila envelope identified on the outside

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Evidence cont.

• The best evidence rule stipulates that the
  original evidence is to be presented whenever
  possible
• Use ultraviolet light to detect invisible laundry
  marks, submit the entire garment to a laboratory,
  identified with a string tag or directly on the
  garment
• Blood can be identified as animal or human and is
  most useful in eliminating suspects
• Age, race, or sex cannot be determined from blood
  samples, but DNA analysis can provide positive
  identification

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DNA Profiling

• Uses material from which chromosomes are made to
  identify individuals positively
• Except for identical twins, no two individuals
  have the same DNA structure
• Introduction of DNA is decided by the courts on a
  case by case method. How the evidence was
  collected and stored is very important in
  deciding if the evidence is relevant.

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Blood and Other Bodily Fluids

• Blood, semen, and urine can all provide valuable
  information.
• Blood can establish that a violent crime was
  committed and movements of the suspect and the
  victim can be recreated by showing blood spatter
  on clothing, the floor, or the walls. It can
  also eliminate someone who is not a suspect.
• Many suspects attempt to remove blood from the
  crime scene which can be easily identified using
  trace solutions such a Luminol.
• New computer programs make bloodstain analysis
  faster. Blood types can be determined from the
  inner core of bones years after the victim has
  died.
• Liquid blood should be collected with an
  eyedropper and put in a test tube. Write the
  pertinent information on medical tape and place
  it on the glass tube.

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Examining Hair

• Hair and fibers are very difficult to locate
  without strong lighting.
• They are extremely valuable because they can
  place a suspect at a crime scene.
• Hair and fiber should be sealed in paper
  envelopes and marked accordingly.
• Hair and fibers usually adhere to blood and flesh.

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Examining Hair

• Microscopic examination determines whether hair
  is animal or human
• Many characteristics can be determined from human
  hair
• The part of the body it came from
• Whether it was bleached or dyed, freshly cut,
  pulled out or burned
• Whether there is blood or semen on it
• Race, sex, and age cannot be determined

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Protecting and Storing Evidence

• Package evidence properly to keep it in
  substantially the same condition in which it was
  found
• Document custody of the evidence at every stage

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Examining Fibers

• Fibers fall into four general groups
• Mineral- Are glass and asbestos
• Vegetable-cotton, jute, manila, kapok, and hemp
• Animal-Primarily wool and silk
• Synthetic-Include rayons, polyester, nylons, and
  others.
• Fibers are more distinguishable than hairs
• They can be tested for origin and color.
• They are looked for mostly in cases of rape and
  assault where there is an exchange of clothing.

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Shoe and Tire Impressions

• If shoe or tire impressions are located they
  should be photographed.
• The items should be submitted to a crime lab if
  they are left on objects than can be moved.
• Never attempt to fit your shoe into the suspects
  shoe print.
• All tires have unique tread patterns, tread wear,
  and road marks that make them totally different
  from other tires.

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Value of Shoe and Tire Prints

• Shoes and tires can show unique tire wear
  patterns that can be compared to the suspects
  shoes and tires
• Footprints can also distinguish weather a person
  was running, walking, or carrying a heavy object
• Tire marks can also show the speed and direction
  of travel, the manufacturer and year they were
  made

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Bite Marks

• Many crimes have been solved due to bite marks
• Usually bite marks involve a series of events
  from culturing for saliva, A,B,or O blood type,
  DNA and microorganisms to photographing the bite
  mark
• Cast impressions are also made of the suspect to
  compare with the actual bite mark

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Tools and Tool Marks

• Common tools such as hammer and screwdrivers are
  used in most crimes
• They cause little suspicion if found in someones
  possession
• These tools are usually found in a suspects
  vehicle or residence
• Tools make impressions in door jams and window
  seals that can later be compared

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Presenting Evidence in Court

• Be able to
• Identify the evidence as that found at the crime
  scene
• Describe exactly where it was found
• Establish its custody from discovery to the
  present
• Voluntarily explain any changes that have
  occurred in the evidence

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Final Disposition of Evidence

• Evidence is either
• Returned to the owner
• Auctioned
• Or destroyed

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The End