He therefore, suggested that punishment must be devised on case to case basis so that it could be free from rigidity and capable of modification with changing social conditions. Dr. Sen emphatically stressed that penal science is not altogether new to Indian criminal jurisprudence.
A well defined penal system did exist in ancient India even in the time of Manu or Kautilya. In ancient penal system, the ruler was expected to be well versed in Rajdharma (duty of king) which included the idea of Karma (duty) and Dand (punishment). The ancient Indian criminal justice administrators were convinced that punishment serves as a check on repetition of crime and prevents law-breaking.
They believed that all theories of punishment whether based on vengeance, retribution, deterrence, expiation or reformation are directed towards a common goal, that is, the protection of society from crime and criminals. Thus, punishment was regarded as a measure of social defence and a means to an end.
The modem trend, however, is to replace retributive and deterrent methods by reformative and corrective measures, the object being rehabilitation of the offender. Commenting on this aspect of penal justice, Dr. P.K. Sen asserted that the concept of punishment has now radically changed inasmuch as it is no longer regarded as a reaction of the aggrieved party against the wrong-doer but has become an instrument of social defence for the protection of society against crime.