According to Roman tradition, it was a Decemvirate (, 'decemvirs with consular power for writing laws') that drew up the Twelve Tables of Roman law.
Background
The setting up of the decemviri consulari imperio legibus scribundis occurred within the context of the two-hundred-year Conflict of the Orders between the patrician order (the aristocracy) and the plebeian order (the commoners). The patricians had developed into the upper class by monopolising the priesthoods, which played an important part in the politics of archaic Rome and, in the Early Republic, the consulship (the office of the two annual elected heads of the Roman Republic and the army), and the seats of the (unelected) senate, the advisory body for the consuls. They were also large landowners. The form of labour exploitation during this archaic period was the nexum, which was what historians call debt bondage, bonded labour, or debt slavery. The debtor pledged his labour services as collateral for debt. Defaulting debtors were liable to have their labour bonded for life.Cornell, T.J., The Beginnings of Rome, p. 266
In the early 5th century BC there was an increase in the problem of indebtedness due to the appropriation of public land (ager publicus) by the rich landowners to expand their estates (which restricted the amount of land available to small farmers), Rome's territory being attacked by neighbouring peoples, and taxation. This also led to an increase in the problem of the abuse of defaulting debtors. Because of the absence of clearly defined laws and judicial procedures, the creditors could imprison and torture the debtors and, sometimes, sell them as slaves. This led to the First Plebeian Secession (494 BC), which was the start of the Conflict of the Orders.
The plebeians demanded that the state protect small farmers from the abuse of defaulting debtors by the creditors, who were the wealthy patrician landowners. When this was not forthcoming, they resorted to boycotting the military levy. At that time the Roman army was a part-time militia of peasant farmers who were drafted each year for the military campaigning season and then went back to their farms. Refusing the call-up gave plebeians significant political leverage. When their demands were not met, on their return from a defensive military campaign the soldiers refused to obey orders and seceded to Mons Sacer, outside Rome. They threatened to stay there until their demands were met. There were negotiations and the secession ended.
However, the plebeian demands were not fully met. Rather, they obtained the recognition of the institutions which they had created during the rebellion, the Plebeian Council (an assembly restricted to plebeians where they could debate their issues) Cornell, The Beginnings of Rome, pp. 260–262 and the plebeian tribunes.Cornell, T. J., The Beginnings of Rome, pp. 259–260 The latter acted as the defenders of the plebeians from abuse by consuls or officials through the provocatio, the power to veto the actions of the consuls and officials. They used it for actions they judged inequitable or abusive to any plebeian. They also convened and presided over the Plebeian Council and presented bills for its vote. An element of this conflict was about whether the resolutions of this council should be binding on all Roman citizens, including the patricians, or only on the plebeians. The plebeian institutions were parallel and separate from that of the Roman state (the consuls, the senate and the two other popular assemblies). Livy said "[t]wo states had been created out of one; each faction had its own magistrates [officials], its own laws."Livy, The History of Rome, 2.44.9 The main role of the plebeian institutions in the early days of the conflict of the orders was self-defence.Raaflaub, (ed.), chapter 7, From Protection and Decense to Offense and Participation: Stages in the Conflict of the Orders
The next step in the conflict was the Lex Terentilia proposed by Gaius Terentilius Harsa, a plebeian tribune, in 462 BC. It provided for a five-man commission to set out the norms through which the power of the consuls would be defined. With the overthrow of the monarchy and the establishment of the republic, the powers of the king were transferred to the consuls, who were regarded as the representatives of regal power.Polybius, Histories, 6.11,Cicero, On the Laws, 3.3 As such, consular powers were undefined and therefore without limits. Gaius Terentilus wanted to have them defined, and therefore curtailed, as a way of proving further protections for the plebeians. The patricians were opposed to this curtailment and managed to postpone the debate on this law for eight years. In 454 BC the plebeian tribunes dropped the fruitless pursuit of this law. They asked the senate to “consent to the appointment of a body of legislators, chosen in equal numbers from plebeians and patricians to enact what would be useful to both orders and secure equal liberty for each”.Livy, The History of Rome, 3.32 The patricians replied that this was worthy of consideration, but said that only patricians could legislate. Although disputed by historians such as Niebuhr, Cornell and Grant, according to Livy and Dionysius, three envoys were sent to Athens to study the Law of Solon and inquire about the laws of other Greek city-states.
In 452 BC the envoys “returned with the laws of Athens.” The plebeian tribunes pressed to begin the compilation of the laws. It was agreed to appoint decemviri with consular powers which would not be subject to appeal and to suspend both the consulship and the plebeian tribunate.Clay, Agnes (1911). "Decemviri". In Chisholm, Hugh. Encyclopædia Britannica 7 (11th ed.). Cambridge University Press. This made the decemvirate an extraordinary magistracy (a governing body with extraordinary powers) as well as a commission tasked with compiling laws. After a long debate about whether plebeians should sit on the decemvirate, the plebeian tribunes agreed to a patrician-only panel in exchange for a law they had passed not being repealed.Livy, The history of Rome, 3.33
First decemvirate
The decemviri took office in 451 BC. Both consuls elect, Appius Claudius Crassus Inregillensis Sabinus and Titus Genucius Augurinus, resigned. So did the other magistrates and the plebeian tribunes. In compensation for their loss of office, Appius Claudius and Titus Genucius were appointed to the decemviri. So was one of the consuls of the previous year (452 BC), Publius Sestius Capitolinus Vaticanus, because he had put the proposal to the senate despite the opposition of his colleague. The three envoys were also part of the decemviri.Livy, The History of Rome, 3.33.3-5 The most influential member was Appius Claudius who, according to Livy, "was the guiding hand in the whole magistracy ... thanks to the favour of the plebs."Livy, The History of Rome, 3.33.7 Each day a different decemvir presided over the magistracy and this man had the twelve lictors (the bodyguards of the consuls) with fasces (bound bundles of rods which were the symbol of supreme authority and sometimes had axes). Their rule was fair and their administration of justice was exemplary. Despite not being subject to appeal, they yielded to one another when an appeal was taken. They drafted their laws on ten bronze tables and presented them to the people, asked for feedback and amended them accordingly. They were approved by the higher popular assembly, the Assembly of the Soldiers. There was a general feeling that two more tables were needed to have a corpus of all Roman law. It was decided to elect a new decemvirate.Livy, The History of Rome, 3.33.7-10, 34
The first decemvirate consisted of: Appius Claudius Crassus Inregillensis Sabinus Titus Genucius Augurinus Titus Veturius Geminus Cicurinus Gaius Julius Iullus Aulus Manlius Vulso Servius Sulpicius Camerinus Cornutus Publius Sestius Capitolinus Vaticanus Publius Curiatius Fistus Trigeminus Titus Romilius Rocus Vaticanus Spurius Postumius Albus Regillensis
Second decemvirate Many men canvassed for election to the second decemvirate. According to Livy, Appius Claudius rigged the election and announced the election of himself and nine men who were his supporters. This new decemvirate became tyrannical. All the ten men had twelve lictors and their fasces had axes (even though the carrying of weapons within the city walls was forbidden). The sight of these 120 lictors terrified everyone. They conducted trials behind closed doors and issued arbitrary judgements. There were rumours that they wanted to rule perpetually. When they issued the two additional tables there was no longer any justification for their rule and people looked forward to elections. However, when the time came, they were not held and the decimviri became violent.Livy, 3.3.35-38.1-2
A Sabine army attacked Roman territory and encamped there and an Aequi army attacked an ally of Rome. According to Livy, the decemviri summoned the senate, but the senators did not show up. To the plebeians this showed the illegitimacy of the decemviri as their term had expired and were now meant to be just private citizens. They were considering boycotting the military draft. However, it turned out that the senators had left and gone to their farms, supposedly in disgust. The senate was summoned again and this time some senators attended. The plebeians saw this as a betrayal of liberty. However, the senators denounced the decemviri and tried to oppose them, called them private citizens and refused to call a levy. In the end they allowed its proclamation of the levy in silence because they feared a popular uprising would bolster the plebeian tribunes, their political adversaries. The plebeians enlisted because they feared violent reprisal as there was no right to appeal. Some of the decemviri led two armies against the two enemies. As they were not good military men, both armies were routed.Livy, 3.3.38-42
According to Livy, Appius Claudius had his eyes on Verginia, the daughter of a plebeian, Lucius Verginius, who was a centurion absent from Rome with the army. Having failed to woo her with money and promises, Appius Claudius decided to seize this opportunity to get one of his men to claim her as his slave. She was dragged off her feet in the forum and the shouts of her nurses attracted a crowd. The claimant said that he was acting lawfully and had summoned her to court. Verginia went to court followed by her friends and acquaintances. The judge was Appius Claudius. The claimant said that the girl was born at his house and then he palmed her off to Verginius as his, but that she still was his slave. Verginia's friends asked for an adjournment until Verginius could attend and to leave Verginia in the custody of the defendants.
Appius Claudius agreed to summon Verginius, but put Verginia in the custody of the claimant. Verginia's lover, Icilius, arrived at the forum, but was stopped by a lictor. He pleaded his case loudly and attracted the attention of the crowd. Verginia's supporters sent a relative and Icilius' brother to quickly go to Verginius' military camp. The claimant pressed Icilius to pay surety to be Verginia's guarantor. Many people offered money and Verginia was bailed to her family.