Cases involving scientific knowledge and the risk of future harm raise a host of new problems in connection with evidence, proof and the finality of adjudicatory decision-making. Indeed, international rules relating to evidence and proof in international courts and tribunals are evolving as a result of the increasingly high incidence of such disputes. Increased use is being made of different methods for the taking of expert evidence; the rules on the allocation of the burden of proof are coming under scrutiny; and the rules ensuring the finality of international adjudication require consideration. This book explores and evaluates the procedural developments that are taking place and assesses further steps to be taken, particularly with a view to recognising and accommodating the precautionary principle.