The bar for discovery in a civil litigation is far lower than the bar for initiating a prosecution. And that's how it should be. If you are convinced that Enron dumped toxic waste in your town on purpose, should you have to prove your case to a point sufficient to initiate a prosecution before you're allowed access to their e-mails? That wouldn't make any sense--the point of discovery is to get all the potentially relevant facts on the table so they can be sorted through.

Also, setting the bar that high for discovery wouldn't make any sense. To initiate an arrest and criminal prosecution, you essentially have to have a "more likely than not he did it" belief in the suspect's guilt. But the "more likely than not" standard is all it takes to win a civil case. So by the time you get enough evidence to initiate a criminal case, you have enough to win a civil case.