Fracking doesn't cause water to become flammable.
Everyone refers to the "oil company" and Jane calls them "Big Oil". Fracking has nothing to do with oil, fracking is essentially mining for gas.
The wall safe in Jason Kern's office is on an outside wall. It's obvious because there is a large window a few feet to it's left. So there is no room in that wall for a safe. Except that the window is set in an alcove. There is a good eighteen inches of wall depth, ample room for a wall safe.
When displaying the initial list of 12 suspects for the case of who killed Ardiles and LaRoche, Cho says they are all people who Ardiles helped prosecute. However one of the suspects is Buddy Hennings, who was never even arrested in the first place let alone prosecuted because it turned out to be his wife who was the killer in the episode he was in.