It is a defense tactic. They are trying to create reasonable doubt by suggesting that someone else may have been behind it - that's a tactic.

As for the 99.9% comment, I was obviously trying to convey my opinion - based on the publicly available and very damning facts - that he has no meaningful chance of acquittal on the most serious counts. It wasn't meant to be a scientifically accurate number (as anyone but perhaps the Sheldon Coopers of the world surely understood). That said, the statistics are pretty close to that: once indicted at the federal level, every defendant on average has a 97% chance of being convicted [1]. Since this case is more airtight and more resources have been expended on it than most, my exaggerated number is not off by more than a few tenths of a percent. It's scary that we live in a country with a conviction rate this high, but it is an undeniable reality.

[1] http://en.wikipedia.org/wiki/Conviction_rate - "For 2012, the US Department of Justice reported a 97% conviction rate."