Through lack of care
Per incuriam is a decision of the court which is mistaken. The one which ignores a contradictory statute or binding authority, and is therefore wrongly decided and of no force. A judgment that is found to have been decided per incuriam does not then have to be followed as precedent by a lower court. In criminal cases, a decision made per incuriam will usually result in the conviction being overturned. The doctrine is an exception to Article 141 of Constitution of India which embodies the precedents as a matter of law.
The present doctrine is strictly and rightly applicable to the maxim ratio decidendi, which is the point that determines the judgement and is binding in nature and not to the obiter dicta i.e. a remark made during the course of the discussion having persuasive value.
In Buta Singh v. Union of India, the Supreme Court held that, when a two-judge bench renders a decision without noticing or in a manner that it ignores the binding decision of a larger bench (in this case a three-judge bench), then such a decision can be said to be per incuriam.
In the State of Assam v. Ripa Sarma, it was held that when a judgment is pronounced in such a manner that is ignorant of earlier judgments of the court by either similar or larger benches, it would be per incuriam. And due to the fact that it falls under this doctrine, the judgment would not be in a position to be elevated to the status of a precedent.
In the State of M.P. v. Narmada Bachao Andolan, the Supreme Court of India held that the principle of per incuriam had been developed by the courts in order to give a lenient approach to the rule of ‘stare decisis’ i.e. to stand by what has previously been decided and give a ruling based on the precedent. Thus, any ruling that is pronounced in either the ignorance of a statute or of any other binding authorities is said to be per incuriam.