The English rule on this matter is in general well settled. It is a common law rule not based on, or limited by, express statutory words. The leading case of R. v. Blake [QB] illustrates the two aspects of it, because that authority shows both what is admissible and what is inadmissible.
What in that case was held to be admissible against the conspirator was the evidence of entries made by his fellow conspirator contained in various documents actually used for carrying out the fraud. But a document not created in the course of carrying out the transaction, but made by one of the conspirators after the fraud was completed, was held to be inadmissible against the other. No doubt what was contained in it amounted to a statement evidencing what had been done and also the common intent with which at the time it had been done, but it had nothing to do with carrying the conspiracy into effect.
Lord Denman said that the evidence must be rejected.