The forensic use of bioinformation

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• The forensic use of bioinformation

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Forensic bioinformation

• Includes
• Fingerprints
• DNA

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Fingerprinting

• The fingerprint is the most commonly used
  method of identification
• No two people have the same fingerprints
  (including identical twins)
• Fingerprints develop before birth and remain
  unchanged throughout life
• Identification relies on the matching of patterns
  and the detection of certain ridge
  characteristics (Galton details)

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DNA sample

• From a person a biological sample taken from an
  individual, usually a swab from the inside of a
  persons cheek
• From the crime scene - samples of biological
  material found at a crime scene that may be taken
  by scene of crime officers include blood, skin
  cells, semen, hair etc

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DNA profiling

• DNA from a sample is extracted, analysed and
  catalogued.
• Sections of DNA are analysed for the presence of
  particular markers
• A DNA profile is a sequence of 20 numbers
  determined by these markers

DNA Profile
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A DNA profile

• Contains genetic information to help identify a
  person
• On average, the chance of another (unrelated)
  person sharing the same 20 number profile as you
  is around one in a billion

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How is bioinformation used by police?
Fingerprints and a DNA sample are taken
Arrest
.
A DNA profile is constructed from the sample
the profile is stored on the National DNA
Database (NDNAD) The sample is kept in a fridge
Fingerprints are sent to NAFIS (National
Automated Fingerprint Identification System) for
checking
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• Police check fingerprints and DNA profiles
  against crime scene samples from unsolved crimes

If the DNA profile or fingerprint of a person
matches a crime scene sample, this may be used as
evidence in court that the person was involved in
the crime
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However.

• Finding a persons DNA or fingerprint at a
  crime scene does not necessarily prove that they
  were involved in the offence

• It could have been planted at the scene, carried
  there on an object, or been transferred there via
  someone elses clothing or shoes
• The person may have been at the crime scene
  legitimately (e.g. they live there) or could be a
  witness/victim

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Using DNA evidence in court

• DNA profiling is generally
• a very reliable way of
• identifying a person
• BUT
• If a crime scene sample contains only tiny
  amounts of DNA, this can sometimes make the DNA
  profiling less reliable
• DNA evidence in court is presented as statistics
  which can be confusing for people in the
  courtroom, including members of the jury
• DNA can be contaminated before, during, or after
  the police and laboratory staff collect it and
  use it care must be taken to try and avoid
  contamination

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Using fingerprint evidence in court

• Fingerprints are hard to analyse and trained
  experts must check them
• Partial fingerprints are even
• harder to analyse
• When fingerprint evidence in used in court,
  juries must be aware that when a match is
  declared, it is never a matter of scientific
  certainty or conclusive fact it is the opinion
  of the expert

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The forensic use of bioinformation quiz
For each of the following statements you must
work out the missing word
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Question 1

• No two people, even identical
• twins, have been found to have
• the same ____________?

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Question 2

• A DNA profile is recorded on the National DNA
  Database as a sequence of ______? numbers

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Question 3

• Fingerprints are stored on a
• database called ___________?

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Question 4
On average the chances of two people sharing the
same complete DNA profile is around one in a
____________?
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Question 5
A DNA ____________? is a biological substance
such as blood, skin, hair or semen