For anyone who thinks or believe that Avery did it, they should admit the actual evidences that points to him being the killer are extremely suspicious. The bottom line was, this man and his poor nephew did not get anything close to a fair trial. Their lawyers were weak and in the case of the nephew, detrimental to the case. But I believe there were a few jurors who would have convicted both of them regardless of what evidence was presented. Whether you believe Steven did it or not, you have to admit there was no definite evidence for it, and almost every evidence has lots of doubts.
I don't think any rational person will rule out he is completely innocent because it is one of those things where "there is a chance but you cannot prove it". The key is, you cannot prove it.
1) The key to the SUV found in his room. It is highly improbable that nothing was found for several days of searching then all of a sudden the guy being sued by him finds a damning evidence in plain sight unless the guy placed it there. This is not a piece of hair or toenail, this is a huge object that no one should ever miss. My theory: The saying "whoever smelt it, dealt it" applies. The guy that found the key, planted it there.
2) The DNA evidence on the SUV key. How could there not be any DNA of anyone else including the true owner on key, while only the DNA of Steven was? If he had the intelligence to scrubbed it clean, why would he put his own DNA on it afterwards? My theory: the framer scrubbed his own DNA off of it, then rub Steven's DNA on it (which he can easily get from a toothbrush)
3) The single bullet in the garage with TH blood. Again, nothing was found for months then all of a sudden, the same guy that found the key finds the bullet? Are the rest of the investigators just completely incompetent or does this guy have ESP? Besides the bullet, there was no trace of any DNA or blood anywhere else in the garage, even between the cracks in the cement which clearly cannot be cleaned/scrubbed easily. My theory: the framer dropped the bullet.
4) Bone fragments and some personal items in the bonfire pit. There were no evidence of the body being dragged anywhere in the property. No single piece of DNA, tissue, or marks. The truth is you cannot really links some body parts found in a fire-pit to the owner of the property as the actual killer.
My theory: the killer saw the bonfire, so he burned the body afterwards somewhere else, collected the few bones necessary to prove the gunshot bullet, then tossed it into whatever is left of the pit afterwards. This is actually the killer and may not be the framer (sheriff) who did this.
5) The SUV found on the property. It was shown by the defense that Colburn called in the plates of this SUV before it was reportedly found. His excuse during the trial for this was he was checking the vehicle's paperwork. This makes no sense as if another officer tells you this is the plate and model of the car we are looking for, there would be absolutely no chance you would ever need to call a dispatcher to verify that. The sheriff (Lent?) then only gave a digital camera ONCE to the person who he suggested to check the vehicle lot, and no one else. My theory: It makes more sense that he was out in the field somewhere and found the vehicle (a little suspicious that he was the one who found it?). Once he verified it was the vehicle, he moved it to the property with the key. Scrubbed his DNA off the key, then gave it to Lent to plant or planted it himself.
6) Steven's blood on the SUV. Why was there clear evidence that the vial containing his blood has been opened and signs of a needle extraction? There would also be no way Steven would not know he's been cut and go back and clean the blood. The EDTA test that "shows" it was fresh blood should be extremely inaccurate with false negatives as all such tests are. These chemical tests that tries to detect the presence of a substance are only accurate for positives at low concentrations, and for them to be accurate for negatives at much higher concentrations. This is the same concept with pregnancy tests, they are more sure that you are pregnant, but not as sure if you are not.
If the FBI was really testing for the presences of the substance from whatever little amount that is picked up in a cotton swap, then they should have tested all 6 samples. Not just 3 out of 6. You only need to test half the samples if you DETECTED the EDTA, not if you did not find it. To more accurately say it wasn't there, they needed to test all 6. The fact they did not shows the bias of the technician.
My theory: the blood was planted from either a fresher sample or the blood evidence was processed to removed EDTA or the EDTA degraded. EDTA is relatively easy to remove or it can be degraded if exposed to a certain wavelength of light. But more importantly the test cannot be deem as accurate for the "absence" of a substance at that low concentration. The fact that the technician claimed that it is based on his methods of ignoring half the samples was so scientifically wrong.
All the evidence that I can see that points to him are directly linked to the Sheriff office (with the exception of maybe #4, but that is still a possibility if the sheriffs had something to do with the death).
Summary of my theory: The sheriffs were being sued for millions, the insurance even stated that this is not covered by their policy, so they would have been held personally responsible. The state would also be responsible financially. There was no way, the sheriffs with all their resources, would not be keeping an eye out on Steven Avery for any sort of slip-ups or misconduct they can use as a defense to their lawsuit. While scoping out SA, they either saw Teresa already killed or (in the worse possible case, killed her themselves, but I believe it was more likely they found her already dead but not by Steven).
Seeing an opportunity to get out of their lawsuit, they rather frame Steven. I believe if they did find her dead, they would somehow convinced themselves it has to be him who did it, even if there was no evidence he did it. Because if they had any morals, they needed to convince themselves it was him for them to believe they are doing the right thing by planting evidence. I'm sure in their minds, planting evidence against a guilty person is different than framing an innocent person, so they would have to convince themselves that they are planting and not framing.
So who killed TH? Besides the killer, only Colburn or Lent (whoever planted the key) would know. But someone on my suspect list would be the brother-in-law, Scott Tadych. There is very little reason why he should be hating Steven so much unless he is the killer. Because he should know his son-in-law is innocent from what his wife and the recant of the kid says. Yet he goes on to say Steven deserved the guilty conviction, even though if Steven was found guilty, there's a good chance his son-in-law will be found guilty too. At no time, it seems like he supported either of them (at least from the show). His timeline of when he went hunting or saw TH was clearly wrong based on a creditable account of the bus driver.
Scott's motive? Perhaps envious that Steven will come into such a huge sum of money, which Scott will have no gain in. Steven coming into that much money may boost his family and his relatives fortunes and Scott might realized that could negatively affect his marriage (if his wife divorces him, she would have a lot of financial support to do so now). Clearly he doesn't care about his son-in-law, so the marriage can't be that great. On a darker and less probable side, perhaps he was working with the sheriffs somehow and called them in afterwards to the body and provided the necessary means for them to plant this all on Steve.