If you leave your child alone (under 16) how far can you go?

Depends on the age of the kid. In the McCann's case, the child was only 4 and should not have been left at all - least of all with two other kids even younger than she was. By the age of 8 I'd leave my child to quickly go and get a pint of milk or similar. By the age of 12, my child could get herself to school and back and be left for an hour or so if I was not able to be at home. By the age of 14, I would consider myself a bad parent if my child did not have the ability and common sense to be left home alone for a day. Lets face it, 60 years ago this was the school leaving age and kids went out to work at this age. If you can't leave your kid at that age you have molly coddled them and not done them any favours.