These people committed the systematic, deliberate, and stealthy statistical murders of dozens of US citizens. They deserve no benefit of the doubt whatsoever. They knew exactly what they were doing. "Just following orders" was not a valid defense at the Nuremberg trials and it should not be here either.
Throw everyone we can get our hands on in jail pour encourager les autres. Once it becomes clear that anyone participating in such a scheme, at any level, faces years in prison, it will be less likely to happen again, and as a direct result hundreds of fewer Americans will not be murdered by illegal air pollution in the future.