Trials do not follow the scientific method...
Haven't read all the comments but my opine on this is the following:
He was convicted for 10 years by a court presumably relying on the testimony of "experts".
If I know what documents are supposed to be on your computer it seems to me that it should be a relatively trivial (emphasis on relatively) task to figure out a "Key" that would demonstrably expose those exact documents from the noise that a good encryption utility is supposed to generate.
The only thing standing between the prosecution and a conviction is the defense's "expert" and how diligent that person is.
The jury would be selected based on their ignorance of such matters as seems to be usual in these types of cases.