 The Bill of Middlesex exploited the King 's Bench 's remaining criminal jurisdiction over Middlesex . Prior to the introduction of bills , a writ would have to be issued , with different writs depending on the issue . If A wished to sue B for trespass , debt and detinue , the court would have to issue an individual writ for each action , with associated delays and costs for A , and then ensure that B appeared in court . Bills , on the other hand , were traditionally used against court officials and the court 's prisoners ; as such , the defendant was assumed to already be in the court 's custody and presence in court was unnecessary . Thus a legal fiction arose ; if A wished to sue B for trespass , debt and detinue , he would have a writ issued for trespass . B would be arrested as a result , and the detinue and debt actions undertaken by bill after he had been detained . Eventually it became even more fictitious ; if A wished to sue B merely for debt and detinue , a trespass writ would be obtained and then quietly dismissed when B was detained in custody . This was originally undertaken through getting a writ of trespass from the Chancery , but eventually a shorter workaround was used ; as the King 's Bench retained criminal jurisdiction over Middlesex , the trespass ( which was fictitious anyway ) would be said to have occurred in that county , allowing the King 's Bench to issue its own bill of arrest . This became known as the Bill of Middlesex , and undermined the jurisdiction of the Court of Common Pleas , which normally dealt with such civil cases . 
