Likelihood of Defence Version of Events

The purpose of this exercise is to demonstrate that a large number of improbable events have to occur in order for Robin to have committed the murders in the manner described by the Defence. A probability of 1 (unity) does not mean that there is 100% certainty that the event occurred for the reason described, simply that there is evidence to support that it did occur and no evidence that contradicts and so it has no effect on the balance of probabilities and carries the same weight as an event totally irrelevant to the crime.