Falsus in uno, falsus in omnibus [Lat.] False in one, false in all. This maxim may properly be applied in those cases only where a witness speaks to a fact with reference to which he cannot be presumed liable to mistake.
The maxim falsus in uno, falsus in omnibus (false in one thing, false in every thing) is neither a sound rule of law nor a rule of practice. Hardly one comes across a witness whose evidence does not contain a grain of untruth or at any rate exaggerations, embroideries or embellishments, Vgar Ahir v. State of Bihar, AIR 1965 SC 277 (279).
The maxium 'falsus in uno, falsus in omnibus' has no application in India and the witnesses cannot be branded as liars. The maxim 'falsus in uno, falsus in omnibus' has not received general acceptance nor has this maxim come to occupy the status of rule of law. It is merely a rule of caution. All that it amounts to is that in such cases testimony may be disregarded, and not that it must be discarded. The doctrine merely involves the question of weight of evidence which a court may apply in a given set of circumstances, but it is not what may be called 'a mandatory rule of evidence', Ram Udgar Singh v. State of Bihar, (2004) 10 SCC 443 (447).