On the outskirts of conspiracy theories has been the claim that the US government created HIV in a laboratory, always with nothing supporting it other than the fact that it makes the US look bad. A few weeks ago I ran across a report, possibly the original Jakob Segal report from the '80s, which raised the quality of these claims by bringing verifiable (or debunkable) facts to the discussion. The report identified HIV as being a combination of two known viruses, identified the leading researcher of one of these two viruses as the head of an "anti-cancer" program at Fort Detrick, and proposed that HIV was introduced accidentally through hepatitis vaccine tests in prisoners in San Francisco and New York, with observation of the subjects ending when no symptoms showed after six months. These claims have a high barrier to validation. You would have to be a bioresearcher with access to a laboratory and/or have access to the classified program records at Fort Detrick to be able to debunk any of them. Let's say the people at Fort Detrick do look at their records and say it's not true. If you are disinclined to trust anything the government says, are you going to believe them?
As it turns out, the Segal report was part of a Communist disinformation campaign known as Operation Infektion. The bulk of this Wikipedia article was written by one SilverJade10, who created an account just for it, and cites Thomas Boghardt's report on Opertation Infektion and two US government reports, "Soviet Influence Activities: A Report on Active Measures and Propaganda 1987-1988" and "Soviet Active Measures in the Era of Glasnost". Wikipedia being Wikipedia, there is already an objection that the sources are unreliable because they are American. In addition, a few sites on the web say that DNA sequencing of HIV disproves the core claim of it being a combination of the two known viruses. I believe it. Time and technology have been sufficient to settle this question.
Side note: one reporter on the Segal claims was one Ian Johnson of the Baltimore Sun. I suspect he may be the same person as Ian Denis Johnson, author of "A Mosque In Munich", a history of al-Qaeda in Europe that I have not gotten around to reading but have heard is good.