Any way to prove that they were aware of it when selling ?
Argument for the defense. But the timing of the sale is so extremely suspicious, and the level of these executives so high that it would require us to believe in
very poor internal communication and reporting structure for them to not have been aware. It will have to be brought out into the light of day.
In a normal corporate environment, when something this serious happens, the very first step is to run the information up the chain. Notifying the CEO, CFO, COO, etc would happen on Day 1 (probably within Hour 1). An emergency meeting to discuss and plan is a definite. There will be a paper trail of this communication. Burden of proof will be on prosecution to discover it and unless the evidence has been tampered with they should be able to demonstrate conclusively who, what, and when. Absence of a trail would be extremely suspicious.
I'm no lawyer, so I dunno what has to happen in order for enforcement to get their hands on the company's emails and calendar records and such. Interview exec admins. Get warrants. Order a record hold. Open up the whistleblower lines. But if they're not already doing it, they are IMO negligent in their duties.