The review recorded that safety cases have not been adopted based on empirical evidence of effectiveness in industry. Instead, they have been adopted based upon the face validity that explicitly communicating the safety reasoning and evidence for a system is better than keeping this reasoning implicit. Apart from mostly academic case studies and industrial papers reporting anecdotal evidence, there is no empirical evidence that regulation based upon a safety case approach is more effective than regulation that does not require the explicit production of safety cases (Leveson, 2011; Wassyng et al., 2011; Hopkins, 2012). In fact, the airborne side of civil aviation, known for its rigorous and transparent safety
practices and extremely low rates of accidents, does not require safety cases to be produced as part of its certification regime. The same can be said about certain defence systems in the US (Leveson, 2011). A review on the effectiveness of the COMAH regulations (that require safety cases) concluded that there was no direct evidence that the introduction of the regulations had
resulted in a reduction in accident risks (HSE, 2006a). Serious criticisms were also raised by the Haddon-Cave review into the Nimrod accident concerning safety case practices, regarding both the
construction and assessment of safety cases (Haddon-Cave, 2009).