The exception of per incuriam under the doctrine of precedents can be understood in two ways. Per incuriam means “carelessness”, although in practice it is understood as per ignorantiam, meaning ignorance of law. When courts ignore law and proceed to pass judgment, the said decision falls under the spectrum of per incuriam and does not necessarily need to be followed.

In 2015, the Court in Hyder Consulting (UK) Ltd. v. State of Orissa held,

“A decision can be said to be given per incuriam when the court of record has acted in ignorance of any previous decision of its own, or a subordinate court has acted in ignorance of a decision of the court of record.

As regards the judgments of this Court rendered per incuriam, it cannot be said that this Court has “declared the law” on a given subject-matter, if the relevant law was not duly considered by this Court in its decision. The ‘per incuriam’ rule is strictly and correctly applicable to the ratio decidendi and not to obiter dicta.

Per Incuriam is a latin term Per means through and Incuriam means lack of care
If any decision or judgement given by any court of law in ignorance of Statutory provisions and precedents is known as per incuriam.

What is a precedent:

High Court and Supreme Court decisions are to be considered as precedent.
As per section 141 of Indian Constitution Law declared by Supreme Court to be binding on all Courts within the territory of india.

Effect of Per incuriam

• Not to be treated as Precedent hence no binding value.
• Principle of res judicata does not apply to decisions given per incuriam

Case Laws

Gurbaksh Singh Sibbia vs State of Punjab 1980

This judgement has set precedent regarding the anticipatory bail under section 438 Crpc. This judgement was given by the Constitutional bench of 5 judges.
After there were following judgements in same matter but have totally reverse view that of Sibbia Judgement :

In the case of Siddharam Mhetre vs State of Maharashtra and Ors 2010 all above five judgements of the Supreme Court held to be per incuriam because :

1. They have not followed the precedent by Constitutional Bench of 5 Judges in Sibbia case and number of judges are lesser than that bench in these 5 judgements.
2. These orders were creating confusion in the minds of Lower Courts . So in order to indemnify the consistency of law.