What is understood by sudden and unexpected death (across countries)?

I am at present engaged in quality research about death in Hospitals (Norway). Last year it was claimed that errors or adverse events is linked to nearly 1/3 of deaths in Norwegian hospitals in 2010 (see attachment, there is a short summary in English in the text). Currently we review all deaths in our own hospital (Haukeland University Hospital), and we strive to find good definitions for what we could define as a sudden and/or unexpected death. Suggestions?