Human beings are generally prone to commit sins due to certain basic weaknesses inherent in the psycho-physical system. For instance, hunger and sex or passions and prejudices. When they are not sublimated or controlled or not let out through outlets approved by dharma (righteousness or religious laws) sin will result. A sin is generally termed ‘pātaka,’ that which makes one fall (pat = to fall), from the ideal.
The smṛtis and dharmaśāstras have categorised the sins in various ways. Anupātaka is one such, considered less than mahāpātaka (grievous sin) but in effect almost approaches it. False accusations against one’s guru (father or preceptor) and sexual relationship with women like the wife of a learned brāhmaṇa or those seeking one’s protection are two such sins.
A sin must be expiated. Various kinds of expiations known as prāyaścittas are prescribed for the various crimes. As regards the anupātakas, the prāyaścittas are almost the same as the ones prescribed for the mahāpātakas. Performing Aśva-medha sacrifice and visiting places of pilgrimage are prominently mentioned in this list of prāyaścittas for the anupātakas.