The Nobel Foundation's no-posthumous-award rule was broken by circumstance exactly twice before 1974 — Karlfeldt (1931) and Hammarskjöld (1961)

The Nobel Foundation's statutes bar awarding a prize posthumously. Before the rule was tightened in 1974, however, two laureates received prizes after their deaths because the awarding decisions had already been reached: Erik Axel Karlfeldt (Literature, 1931) and Dag Hammarskjöld (Peace, 1961). Hammarskjöld — UN Secretary-General, killed in a 1961 plane crash during the Congo Crisis — is the only Nobel Peace Prize laureate ever awarded posthumously.

The 1974 statute revision narrowed the exception: a prize may be given posthumously only when the laureate dies after the announcement but before the December ceremony. On that clause, the sole case since is economist William Vickrey, who died in October 1996 days after his award was announced. This rule is the mechanism that connects Hammarskjöld's case to Ralph Steinman's 2011 medicine prize, which was allowed to stand only because the committee's decision predated news of his death.

[unverified-historical — needs Tier 1–2 primary] The capture assembled this enumeration and the specific dates (1931, 1961, 1974, 1996) from a WebSearch synthesis with, in its own words, "no single URL," cross-referenced against NobelPrize.org summaries. The dates are recorded here from Tier-4 encyclopedia corroboration only; the authoritative source is the Nobel Foundation's published statutes. See question-verify-nobel-posthumous-statute-history. Held at seedling pending that primary.