I believe they planted the evidence specifically to be seem so far over-the-top that it would force Avery to settle his civil suit at the low dollar value he did. I think the fact that it lead to him being convicted is the part that eventually screws the MCSD.

If Avery is acquitted of the Halbach 'murder', they've got it made in the shade. No prospect of losing a giant, uninsured settlement, no admission of wrongdoing (part of the settlement was no admission of any wrongdoing), they've got no real need to investigate the Halbach death any further. Avery has his freedom, but whatever sympathy he has from the public is gone with the hit to reputation of being charged with homicide. People are always going to think he did it and I suspect that would've lead to his untimely departure from this world in one way or another.

The worst thing that could've happened to the MCSD is what has happened. The runty piece of white trash they picked on because it was easy has against all odds become a symbol of innocence and a cause for the masses and the MCSD has become the world's go to reference as corrupt law enforcement.

That's the thing about power. It convinces people that have acquired it that they are smarter and not subject to the rules like those who haven't acquired it. The scales of justice are out of balance and it can't stay that way forever.

Someone like Kathleen Zellner is the catalyst to turn the arrogance into avarice as the people most responsible come to realize they can't circle the wagons enough to cover themselves. People are going to have to be silenced, the only way to keep a secret among three people is if two of them aren't living anymore. Get your popcorn.