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Guess who?

Understanding how the DNA intelligence information can be used by the police to prioritise investigative leads.

Sample DJT/1 was a swab taken from the blood drops found near the crime scene, potentially belonging to a person of interest in this case – if a plausible scenario is that a fight occurred, then it is possible the other party was also injured and bleeding. The DNA from this sample did not match anyone on the national DNA database, so has subsequently been analysed using the DNA intelligence techniques described in the last three steps. This analysis was carried out to give an estimation of the eye colour, hair colour, biogeographic ancestry and age of the individual whose blood was found. The tests gave the following results:

  • There is a high probability that this person has European bio-geographical ancestry (ie their ancestors generally have a European ancestry, which would include individuals in the UK that would self-declare on the census as White British, White Irish or White Other – a category which could include for example individuals born in Europe, America, Australia etc).
  • They are predicted to be approximately of age 26 with an average prediction error of +/-4 years (which translates to a 52 percent chance that their age lies within 4 years of the predicted value, i.e. the real age is between 22-30, and an 86 percent chance of the true age being within 7 years of the predicted value, ie between 19-33)
  • They are predicted with 73 percent certainty to have green eyes
  • They are predicted with 79 percent certainty to have brown hair.
  • They are male.

This information has now been given to the investigating officers who have obtained some CCTV images from the crime scene area at the suspected time of the incident. Using this information, can you narrow down this list of images to help the officers work out which of these people is more likely to be the person who was bleeding and left the blood drops on the pavement?

Suspect One

Suspect Two

Suspect Three

Suspect Four

Suspect Five

Suspect Six

Suspect Seven

Suspect Eight

Suspect Nine

Suspect Ten

Suspect Eleven

Suspect Twelve

Suspect Thirteen

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The Science Behind Forensic Science

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