I don't think they start out to frame people in most cases, I don't even think framing someone is necessarily the right term. I think they get tunnel vision and make statements that fit their tunnel vision, and then when something does not fit they ignore things that are outside their tunnel vision or make excuses for them. They have talked themselves into a box, and will look less than stellar on a murder case if they suddenly start changing direction.
The cell phone was beyond an amateurish mistake and now they are trying to dismiss it, make us believe they were not familiar with phones like that and besides it was not important, there was no evidence on it when at the same time they want every piece of BC's electronics to be relevant. When you got the first message on the phone that if you proceed all will be erased, especially when you are going off memory from a phone call with AT&T a couple of weeks before, then it would be prudent to stop and re-think your strategy. Then to not let the Defense know for 10 months that you did wipe the phone, it causes everything else that you did into question. How are we to know though that they did not get into the phone and erased it after they read it because the evidence on it did not fit their scenario of the crime.
Then there is the computer, they took possesion of it and protocal was to secure it by turning it off, but they left it on for 27 hours. Even the FBI agent was surprised to hear that. They are now saying that they left it on for 27 hours because they were afraid of losing or corrupting data, but we know now data was corrupted in the sense that it changed in those 27 hours. The question here is why was it ok to turn it off at 27 hours that did not make it ok to turn off at 10 hours, 18 hours, or 26 hours, anytime before that 27 hours? Why not a concern at 27 hours data would be corrupted?
Their own actions are causing them to be questioned. They are also human with all the faults of humanity regardless that they wear badges.