I'm on pins and needles about next episode, so in case any of you didn't see that, here:
http://www.nbc.com/chicago-fire/photos/sneak-peek-spartacus/2345721
http://youtu.be/xnJwWpMXtjY
http://youtu.be/mQhZ-08sPYc
It's just my speculation, but I think that Nesbitt specifically chosen Casey to mislead the police. But Casey will understand that and then someway find out the truth, probably Katia will help him in that.