Researchers pointed out flaws in the statistical evidence underpinning the DNA retention policy, leading to a revision of the scientific work.


  • A review carried out by ESRC-funded researchers revealed that sample storage of DNA was based on flawed statistical evidence.
  • The review resulted in a major revision of the scientific work on DNA retention.
  • The findings led to a new policy report (DNA Retention Policy: Re-Arrest Hazard Rate Analysis) and a change in policy on retention periods.

About the research

The extensive storing of DNA samples for the national crime database has proved controversial. Following flawed statistical evidence in a Home Office consultation document (Keeping the Right People on the DNA Database: Science and Public Protection, May 2009), a review of the government policy on retention of DNA samples was carried out by the ESRC National Centre for Research Methods/Lancaster-Warwick-Stirling node.

The review concluded that a proposed six-year DNA retention period for people arrested for crime was built on flawed statistical evidence. The period was calculated from the 'first official process', instead of the most recent arrest where DNA retention would be restarted. In addition, rapid re-offending by persistent criminals was not taken into account.

The research was led by Professor Brian Francis and Professor Keith Soothill as part of the programme 'Developing statistical modelling in the social sciences Phase 2'.