Substantial body of experience: there is a substantial body of experience with safety case development within the UK defence domain. The domain has
now lived with the cross-service requirement for safety cases for over fifteen years. As the Nimrod Review Report discusses, in this period there have
been examples of poor safety cases alongside positive examples (Haddon-Cave, 2009). There is therefore much to learn from safety case practice in the
UK defence domain
Clarity of approach: positive features to observe include clear regulatory standards (such as Defence Standard 00-56), clear definitions, and the practice
of producing explicit and structured safety arguments
Risk of complacency: negative experiences to note include where safety case development appears to have become a ‘paper exercise’ through lack of
stakeholder engagement, where the focus of safety management has been on maintaining safety case argumentation rather than maintaining the
safety of the system, and where safety cases have not been used or allowed to influence and change practice
Lack of organisational support: Further barriers to effective safety case use are practices where there has been insufficient organisational support for the
MoD’s many roles with respect to safety cases (customer, operator, regulator, owner)
Hierarchy of safety cases: the Defence domain has evolved a clear understanding of the difference between equipment safety cases, and wider
operational safety cases, and that a hierarchy of safety cases are sometimes required in order to establish an overall safety case