Prove the original crime, don’t rely and peripheral procedure like “they lied to a federal agent” (uhh) cop-out. Do your job.
Likewise I’m not don’t of people getting off on “technicalities” (Some more than others)
I think in the absence of actual injuries, the obstruction charge is actually the more serious criminal charge applicable. Which is not an indirect charge; obstruction is a distinct crime with its own harms.