Hmmm, I'm thinking about the police baton as the weapon used to cause the skull fracture. I'm also wondering about other "police" connections to this case -

HiTec boot
"scanned for electronic devices"
"we are familiar with Law enforcement countermeasures and tactics" (note the capital L in Law enforcement - indicating importance of Law enforcement??)
"you and your family are under constant scrutiny as well as the authorities"
"don't think that killing will be difficult"
Ask for ridiculous amount of ransom so that FBI will immediately think something ain't right
Massive undermining of the case by "fellow" law enforcement officers.
Encourage focus on the parents and remain focused on the parents (the starting point of any investigation of the murder of a family member).
Create a secondary focal point (the RN) to muddy the waters
Knowledge of knots
Knowledge of forensic evidence (minimize it)
Use items from the home to make it look like a parent did it
Wrap child in blanket to make it look like parent did it
Tie victim's hands together - like handcuffs
Set screensaver to Ramseys are the Killas

Stretching it, huh?