What did the court decide in Haines v. Kerner?
Answered for: US
We cannot say with assurance that under the allegations of the pro se complaint, which we hold to less stringent standards than formal pleadings drafted by lawyers, it appears 'beyond doubt that the plaintiff can prove no set of facts in support of his claim which would entitle him to relief.'
A per curiam decision holding that a complaint drafted by a self-represented litigant is measured against less demanding pleading standards than one drafted by a lawyer. The sentence above is the court in its own words.
This answer is true in US and nowhere else on this site. Another jurisdiction is another answer, or an honest gap: see what has been read for US.