Could It Have Been An Accidental Death?

If it were an accident, why would they need to cover it up, dispose of the body and file a false police report?

Think of it like this, if it were truly an accident, why would they make it look like a homicide?

The only reason they acted the way they did is because it could not have been explained away as an accident.

There was something so incriminating they could not explain it away, nor allow a post mortem to take place.

Had she died from an accidental overdose of a sedative, it could have been explained away.

Maddie ate the pills thinking they were candy and died whilst the mccanns were sleeping in the apartment.

She woke up and due to the pills which the mccanns didn't know she had eaten, fell behind the sofa and died. 
They only found her the next day when they woke up.

Maddie could have woken during the night gone into the sitting room, had a fit, banged her head and died and they only found her the next day when they woke up.

They could have checked her during the night whilst they were eating and drinking and thought she was asleep when she was really in a coma/dead.

There was something that happened that could not be explained away.

Evidence of long term and ongoing sedation?

Evidence of physical abuse that could not be explained away as the usual rough and tumble of accident prone toddlers?

Evidence of old and healing injuries that had not been treated by their own doctor or in a hospital?

Evidence of sexual abuse which could never be explained away as accidental?

There was something so incriminating, that the mccanns and chums were forced to claim they neglected their children on a nightly basis and risk possible jail terms of up to 10 years (neglect resulting in harm) rather than have the truth be revealed and face a possible life sentence.