When an accident happens the court is not permitted to conclude that the accident happened as a result of negligence. Instead, there ordinarily has to be proof of negligence - that somebody went through a "red light" or acted unreasonably under the circumstances. An exception to this rule is when an injury does not happen ordinarily in the absence of negligence. In that case, we can presume that negligence was the cause of the injury if the person injured was in the complete control of the wrongdoer and nobody else could have caused or contributed to the injury. An example of this is when an individual has a foreign object left inside of them after surgery. The individual doesn't know how the foreign object wound up inside their body but does know that it would not ordinarily happen in the absence of negligence. Under those circumstances, the doctrine of res ipsa locquitor - "the thing speaks for itself" - applies. Because there was a foreign object in the person and that doesn't happen in the absence of negligence under the circumstances that speaks for itself and negligence is the only reasonable explanation.