The video of the lawyer?

It was wishful thinking on Stone's part. He believed that if the judge saw the inappropriate relationship between Nas and his lawyer, that it would show grounds for a mistrial due to an obvious conflict of interest. Stone didn't think there was any chance Nas was going to be found not-guilty and basically did this out of desperation. If he DID get a mistrial, there was a slim chance the prosecution would drop the charges rather than investing more time, money, and resources into another lengthy trial.

Yeah, I know, replying to a 7 year-old comment...

Stone warned Chandra against putting Naz on the witness stand. She did it anyway and it backfired so badly, she was in tears after the prosecutions' cross-examination. As a result, Stone said that their chances of winning went from 10% to zero.

So, try for a mistrial. Sacrifice Chandra because she was the one who screwed up (twice). In the retrial, don't put Naz on the stand and have at least some chance of getting him freed.