The jurists rapidly expanded the meaning of these terms and the cases in which damage could be claimed.  Ulpian defined the terms in 18th book Ad edictum: occidere:; 9; (p. 72-73) 11.1-5 (p. 76).  Ulpian defines occidere in (p. 73) as being necessary with force.  But also defines it as when (p. 74) someone drops or throws something and kills, and if a doctor operates unskillfully (p. 75).  Ulpian 9.2.9 distinguishes between delivering the cause of death with one's own hands or providing the cause.  Celsus makes the distinction between direct and indirect cause of death.