OJ was proved guilty 9 ways from Sunday. The reason he was acquitted was partly because the prosecution was not handled well, but mostly because the jury refused to do their duty. There was overwhelming evidence of guilt quite apart from the DNA evidence. You should read Vincent Bugliosi's book on the trial.

It is very early days to be talking about DSK being 'convicted' of anything. We have only press reports about samples, and nothing has been presented in court. However, with a suitable sample and modern techniques identity can be proved to a much higher degree of certainty than 1 in 85,000. I can't explain the science behind it unfortunately.