The American States adopted the system of Common Law Pleading along with the substantive common law. Some states, as for example Illinois, still retain this system almost in its entirety. In most states however great changes have been made in the adjective side of the law. About one-half of the states have adopted a general set of laws commonly known as Codes, by which not only the common law system of pleading, but also even the distinction between law and equity, has been abolished; and a new and simplified system of pleading and practice adopted, with a single form of action capable of being adapted to meet the conditions of every case. All existing legal rights, however, are retained under these codes and can be enforced under the new system.

The laws of evidence have also undergone many changes in recent years, and many of the unreasonable technicalities of the ancient rules swept away. These changes will be considered under the subject of Evidence.