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.

According to the precautionary principle, action to counter a serious threat to human health or the environment should not be delayed merely because of scientific uncertainty. The need to protect human life or health and the environment should be assumed, once certain thresholds are crossed. Proving that harm will occur is not required. This approach sits awkwardly with the usual precepts of adjudication, which revolve around the proof of fact. The challenge is for adjudicators to make reasoned decisions that pay due heed to the harm that is threatened in every dispute, despite the absence of perfect knowledge.