> Isn't there a defence?
There is, but it's a resource battle. Governments and large corporations can spend a hundred times more hours on something than regular individuals and small nonprofits. If they both had the same resources there might be a 90% chance the defendant wins, but create a large enough resource asymmetry and it flips the other way.
This is one of the main reasons for the "beyond a reasonable doubt" standard in criminal cases, but that doesn't apply to civil cases even when the plaintiff is 10,000 times the size of the defendant, and isn't enough in criminal cases where the defendant is relying on a criminally over-worked public defender and everything is greased to mass-produce guilty pleas and discourage trials.
> I also don't believe the court would like to find out that the prosecutor lied.
It isn't strictly lying, it's just not pointing out inconvenient facts.
Prosecutors can get into trouble for this when it's really damning, like not disclosing a witness who says it was somebody else, but that's separate from all the banality like the number of man hours they spent investigating you without finding anything before they could come up with what they're presenting.