Brendan's initial confession on Feb. 27th show classic signs of guided testimony on behalf of the detectives. Mind you, he gave his confession twice that day; first at the high-school, then again a few hours later at a police station with his mother present. Now, the first thing we need to understand is that Brendan's sister is also involved in this. She was the one who told school officials that Brendan may know something, and that Brendan was at the bonfire in Steven's backyard the night of Oct. 31st. She said that he seemed sad and that he'd been losing a bunch of weight, which the detectives attributed to guilt, not the fact that he had just broken up with hist first girlfriend ever (a fact he brings up during the confession).
Much of the initial information the detectives have (from his side) going into this is is from what Brendan's sister alleges he told her (he would say he told no one about this out of fear of repercussion from Steven). So, in the first confession, the detectives keep pushing for items to be included in his confession that are consistent with the evidence that they know is already there. They know that there are tire mesh webbing on Teresa's bones, and they know that a piece of her clothing (a rivet from her jeans) is in those ashes. So, when they are asking for the confession, and he begins missing these points, they keep doubling back and asking again until he eventually tells them what they want to hear.
This first happens with the tire. They ask him what was in the fire when he first gets there, and he says just branches and stuff. Then they ask him if there were any tires, which he replies with no, just branches. Then, when they start asking him about the fire again, they keep asking about tires being in the fire, and BLAM, suddenly he starts saying there are tires in the fire.
The other piece was clothing. They know that her clothes are in there. So they keep asking him if he saw clothing in there, or if the garbage bags he brought out looked like they had clothing. Then they keep peppering him with images of their construction (you saw her clothes didn't you. Did you see blood on her clothes? Were they in the garbage bag?), and after he initially denies this, he starts telling them that yes, there were clothes in the bags, and that he saw them in there, bloody and with a stab wound in the stomach area of the shirt.
The biggest inconsistency was in regards to a cut he describes Steven has. Mind you, these are from the two confessions he gave on the very same day, his first confessions. In confession 1 of that day, they ask him if he had any scratches, and he says yes he did, on his finger. They ask him if Steven told him how he got it, and Brendan says he got it from a piece of glass. Later that same day, Brendan's confession changes - now, Steve has a cut on his arm & his finger, only the cut on his arm came from a piece of glass, and the cut on his finger comes from, and Brendan claims this in the second confession after the detectives ask him if it was from Teresa, that Teresa scratched him while he was stabbing/dealing with her.
We're not even gonna get into the sled part (in confession 1 of that day, Brendan claims Steven offered no details on how he transported the body from the pit to the house, while in confession 2, Brendan says he transported her with a sled).
To me, its pretty clear what happened here - this is a youngster who was close to a story the media was covering extensively and who started placing events into his head since he was so close to it. What do I mean by this? Well, at that time, the media was running rampant with details of the investigation (the bonfire pit in his backyard containing her remains, the jeep being found). Remember, this confession occurs nearly 4 months after the event. So the media is saying Steven had a bonfire & roasted her in his backyard! And its on Halloween night. And several people & Brendan himself realize he was at a bonfire at that backyard that very night. So people start telling him, you must have seen something. Anything. He clearly did it. And now, suddenly, he starts imaging it. I mean, he was RIGHT THERE! He MUST HAVE SEEN SOMETHING. The cops know Brenda was there, he had to have seen it, right? Cause if Brendan didn't see it, then theres no case. In fact, if Brendan states he saw nothing in that bonfire, Steven Avery might be walking out of this thing.
Brendan spends 4 months hearing the news verify that a woman was burned at a bonfire he had attended and hear everyone talk about it, and his mind just started creating details after that.
Here is the key thing you need to remember though - almost none of what he said matches up with the physical evidence actually found. And his story is the most inconsistent story told, ever.