Causation means the causal relationship between defendant's conduct and result. In other words, we can say that Causation provides a means of connecting conduct with an effect which is typically an injury. In criminal law, it is defined as actus reus, which means action, from which that specify injury arose and is combined with mens rea, which means a state of mind to composite the guilt. Causation is supplied where is all it has been achieved and is material concerning inchoate offences. When we establish Causation, it is important to establish legal liability which involves two-stage injury. First is to establish factual Causation and second establish legal Causation. Factual Causation is established before inquiring legal Causation, assessing if the defendant acted in the plaintiff loss. Determining legal Causation involves the question of public policy regarding the situation where, despite the outcome of the factual enquiry, the defendant may never release from liability or impose liability. The method to establish factual Causation is by but-for test. Does this test inquire for defendants act would then have ever occurred? For example, X shoots and wounds Y. It would ask that, but for X’s act would have been wounded Y. The answer is no; then it is concluded that X caused harm to Y. This is a test of necessity. To establish legal Causation, the law says that it will nevertheless not hold the defendant liable because in the circumstances that defendant will not be able to understand in a legal sense as having caused a loss. In the US it is known as the doctrine of proximate cause. The but-for test gives the right answer to problems, but sometimes it gives wrong answers also like if P is critically injured Q. Q is taken into an ambulance, but on the way to the hospital they got stuck due to lightning, she would not have stuck if you would not have been injured. So according to the but-for test, it is clear that it has P caused injury to Q.
The doctrine of terra nullius is observed under international law, justifying the position of a state after they occupy land which comes under the dimensions of the principle of terra nullius.