The Free Association as Evidence Principle . Clay Shaw was a homosexual. Ferrie was a homosexual. After all, all these homosexuals must know each other. No need to show that any two have been in the same place at the same time.
Sexual orientation is enough.
This same principle is applied to all sorts of groups. Jesuits, Cubans, people who work for the government. The Government Documents are Never Mistaken Principle . The bureaucrats who wrote them are never just clueless. Or they may let The Truth slip out.