How did the Roman code of laws develop, and what were some of its basic principles?

The basis of the Roman code of laws was the Twelve Tables, which was created around 450 B.C. during the era of the Roman Republic. Their aim was to set out the basic rights and obligations of the plebeians (people) and to protect them against abuses of power by a small, privileged group of patricians.
The Twelve Tables included laws about the practice of religion, ownership of property, debt, slavery and marriage/divorce, among others, and outlined punishments that would be given for such crimes as theft or practicing black magic.
Later Roman legal reforms, especially the Corpus Juris Civilis, established around 530 A.D. by the Byzantine emperor Justinian, introduced legal concepts that are still fundamental today, including the idea that an accused person is innocent until proven guilty, and would become the basis for many of the world’s legal systems after the Roman Empire fell. Its influence can be seen in the Latin legal terminology used today, such as habeas corpus, subpoena and pro bono.