The problem with the Bill of Rights and other such laws is that in order for the Rights of anyone to be upheld,they must be upheld for all. So even if you don't like your neighbor,and suspect he is up to no good,any search should require a court order,i.e. a warrant describing the place to be searched and the thing or person to be searched for.Now if you don't mind having any official or police officer being able to peek through your windows or enter your property on a whim,then perhaps this constitutional republic is not where you want to live.
Police,when told of the sounds of children playing in the backyard of a convicted sex offender,should have consulted with the parole officer and a judge,and been easily able to get a search warrant.No need for "extra-legal" snooping.