Watched a few of the McCann documentary and echo what has been said in here, leaving kids 3yrs and under alone while you go get pissed with your mates is just absurd, there was a babysitting service for christs sake in the complex, whatever happened they have to live with that guilt, of all people doctors should know about duty of care.
Another thing I learnt and did not know was the twins slept through all the commotion, people rushing about in the apartment looking for Maddie, that is strange, was she sedating them so they could go out drinking?