The solution to the question if Robert Capa's iconic picture of a Loyalist soldier dying in the Spanish civil war in the 1930s was true or false was the subject of an article in the Dutch newspaper NRC Handelsblad on October 9 (the article itself is not in the public part of the website--sorry!). It was a long article, so the answer was not simple.
First of all, the answer did not come from the 'Mexican suitcase', the suitcase full of negatives made by Capa that surfaced in 2008 in Mexico. The negative of the famous photo was not there; it has been missing for years. Second, the state of the art on this question will forever remain a matter of debate between experts and would-be experts. It is, so much we can take from the discussion, probably not a photo of a soldier dying in a large-scale action. Probably Capa went on a small tour with a group of soldiers for a photo shoot; it was a staged photo. Some stories have it that the man in the picture was shot by a sniper at the moment Capa pressed the shutter--to my mind too good a story to be true. It was said that Capa himself never claimed it was a picture 'at the moment of death'.
The impression of authenticity of the photo may have been a trick: Capa may have made a slightly unfocused photo on purpose (no autofocus in those days, of course!), and moved his hands a bit to give the impression he himself was diving for safety while pressing the shutter.
And then there is the role of the press. Capa's picture was first published September 1936 in two French magazines, Vu and Regards. In Vu they published a whole series of the young photographer (he was 22 at the time and not yet famous) with poetic, symbolic captions going with the photos. When the same picture was republished later in world-famous magazine Life in the USA, July 1937, there was a much more dramatic caption, talking about the photo being made at the moment the soldier was killed. Being published in Life, and with such a dramatic caption, were the occasion for Capa to become world-famous--and he did not say that the caption going with his photo was not truthful. He did not even lie, he just did not tell 'the whole truth'. What would I have done--what would you have done--if fame suddenly beckons?
Footnote: the picture can be found on many websites so have a look at Google or better the Wikipedia if you do not know it, but is copyrighted.