Unquestionably, the starkest of the rights that Roman law gave to the pater familias was “the power of life and death” (vitae necisque potestas) over those descendants who were in his paternal power.

This is thought to be a very old institution and is sometimes associated with the kings of Rome (e.g., Papinian, Coll. 4.8.1); it also may have been mentioned in Rome's earliest legal code, the Twelve Tables of 449 style='font-size:6.5pt;line-height: 120%'>B.C.

The fathers right to kill a child, though perhaps never formally rescinded in classical Roman law, is apparently treated as void in A.D. 318/319 by the Christian emperor Constantine (C. 9.17.1 = C.Th. 9.15.1). However, by that date the right to kill one's children was, as it seems, long since obsolete. Actual instances of a pater familias using the right in order to kill a juvenile or an adult child are rare and mainly associated with early Rome, prior to the emergence of a contemporary his­torical record in the late third century B.C. It is therefore difficult to be sure about the historicity of these incidents, though Roman authors do appear to believe that there was a time when the father's power was virtually unrestricted by law.

In classical law, the power of life and death may have survived more as a sym­bolic indicator of the father's general authority and control over his descendants. In practice, the right was hedged round with social restrictions that had grown up to prevent its arbitrary use; above all, the pater was expected not to act without first consulting a consilium, an informal council made up of relatives and close friends, whose function seems often to have been to delay action until cooler heads pre­vailed. But even if the father's right to kill or maim survived only in theory, law did support his right to use corporal punishment against disobedient children, some­times to the extent of letting public officials administer the actual punishment.

Further, not until the later Empire did Roman law restrict the right of the pater familias to cause the abandonment of, or even to kill, newborn infants in his power.

Finally, there is the “right of killing” (ius occidendi) introduced by the Emperor Augustus in a statute of 18 or 17 B.C. that criminalized adultery. One provision of this law allowed a pater familias to kill his daughter and her lover when they were taken in adultery; but this right, which the jurists sometimes treat as related to the vitae necisque potestas, is so restricted by legal, practical, and psychological limita­tions as to cast doubt on its real utility.

Even from an early date, limits on patriapotestas were already enforced when it came into conflict with the state and the civic responsibilities required of Roman citizens. Then the interests of the family yielded to the greater interests of the Roman citizen body.