Funny. It's hard to think of this as a "cold case," having had this murder haunt me personally and given all the time and attention, thought and effort that average citizens have put into it over the years.
This case became cold within the very first hour after the 911 call. The inability of the first officer on the scene to find the body behind a door which he was unable to figure out how to open started the whole cascade of ineptitude. That single act (or omission, in this case) prevented JB's body from being seen by LE in situ and before either parent had handled it. Then French doesn't clear the house of all the extra people. While it is true that at that point they were considering it a kidnapping, the FBI (who were there that morning) told police they would be finding her body. It didn't look like a kidnapping to them, and they were right- it wasn't. Kidnapping involves removal of the victim, even a dead one. So kidnapping or murder or accidental death covered up, the house was an active crime scene either way and police did nothing to secure it. Not to even mention it being unthinkable that the Rs would call over friends, clergy, victims' advocates at THAT time, when the RN said JB's be killed if they talked to anyone, inferring that even their phone was being monitored. So to go ahead and call all those people is simply unthinkable (in a REAL kidnapping). But obviously the parents knew something at that point that no one else did. They knew it was safe to call whomever they wished.
Then Arndt violates professional procedure and moves the body a second time herself AND allows someone to throw a blanket over her AND she herself throws a sweatshirt over her. So much for preserving the crime scene. That was that. The case was forever altered.