Second, "trial balloon defenses" offered to the media to plant seeds of doubt (in an atmosphere where nobody is actually making you pony up proof) are generally acts of desperation, and are pretty transparent. You offer something like that up, you better have something credible and checked out to back it up. If you don't have anything credible, then you don't spread the rumor.
Third, recognize that some people are guilty, and no amount of denial will change the likely outcome at a trial - so in that case, you hammer on the science, you beat on the causal connections, all while begging for a bargain before a verdict.