I have to say, first thought is that Cristina or someone in the government who could have been affected by Nisman's testimony and presentation of evidence seems like an obvious answer to who could have been behind this. But with a number of the articles posted, particularly from BubbleEar, a number of good points are raised.
About the GSR from a .22 caliber pistol: A quick search shows a number of GSR-related articles talking about .22 calibers leaving a residue. They do say that one or more of the three critical elements might be missing or in lower proportion, but only that one link previously in this thread showed that it produced nothing, when I reviewed a few of the Google search results ("GSR from firing 22 caliber"). I may have missed something, it was a quick look. There were discussions of some .22 weapons actually providing more GSR than other guns, depending on the quality of the weapon itself. I don't think the GSR only comes from the center primer, it also seems like it exists with the rim fire as well, unless these were .22 longs and a long doesn't use rim fire?
When thinking about the testing done, we don't even know what kind of testing was done (at least, the article I read didn't meantion the test used). Some tests go as far as using an electron microscope. I don't know what availability of advanced testing might be available here. I'm supposing that it could be that he fired the shot and the tests weren't advanced enough to detect a small amount of GSR from a relatively well-made .22 caliber pistol.
As to some points, the first one is that Nisman couldn't have been working absolutely alone, even if he was given the majority of his "case" from Stiusso and/or associates. Killing Nisman in this case does not kill the evidence. If it was murder, I suppose it could also be said that his murder might be enough of an communication to others not to talk, maybe no one else associated with the case would talk for fear of the same treatment. Then again, I find it hard to believe that someone who was killing Nisman to stop something big from coming out would have depended on that. It may not stop someone else from coming out with the evidence and could lead to bigger problems.
As far as all the evidence being left behind and therefore proving that there is nothing for the government to worry about - well, the government would now have their hands on the information and may be able to lose or change anything that was incriminating - but it just seems like too far a stretch, also when taken with the fact that Nisman couldn't have been literally working alone.
As far as Cristina being real worried about what Nisman was accusing her of - I don't buy that too much either, even if she was guilty of what Nisman was accusing her of. She's done some pretty damaging things to the country and hasn't really taken too much of a hit for it. In addition, she signed this fairly recent deal with China that purportedly has a lot of negative impact for industry and some people are saying part of it's illegal anyway (particularly the part about possibly displacing Argentine workers). She doesn't seem to be suffering too much from this. Is making a deal with Iran to acquit them really worth all of this?
If it was indeed a murder, I seem to think the SIDE folk, or ex-SIDE still associated in some way, are more likely to be the culprits, given their known modus operandi in the past.
Think about who really would gain from this. People are already pissed at Cristina. Even poor people. I can remember a time when most of the poor people I know thought of her as a literal savior (and some of these received the little meal packages and a little bit of money from people working for Cristina, to vote for her). But almost to a person, those who previously liked her think she's ruining the country - and that takes a lot. But she still enjoys a relatively big approval rating after fighting against "Goliath", AKA "the vultures", etc, and I am at least half-expecting that her party wins in October anyway.
To me, the potentially violent opposition to Cristina stands to win from this. They're the only ones, really, that it seems would gain much from this. Discord and a drop in Cristina's ratings from something that people will readily believe at a moment's notice may affect her party's chances somewhat in October. Problem I see with that is that it's still a long time until October, but if Nisman had presented a bunch of garbage that ended up making no sense, it wouldn't do to take him out after he testified.
I doubt the suicide theory a bit more than I doubt the murder theory. It could be that he realized he was being set up and killed himself - but what was the setup for in the first place if not to damage Cristina (I'm assuming it wasn't Cristina in this case)? Just to damage Nisman himself? Why would Stiusso give Nisman bad information unless he was hoping Nisman would make an ass of himself and have some manner of making things look like they look today? Could Stiusso have been certain that Nisman would have committed suicide the day before he was to testify even if the guy realized he'd been set up?
Out of all of this, I just really doubt that Nisman killed himself, but it's possible, still, even with the GSR results.
