Mona_b seems to know a lot about the law, perhaps PM her
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Even if they ring the doorbell and nobody is home, I still don't think that gives them the right to look into windows or take pictures without a warrant. Police could use that defense all the time to peek into windows and take pictures. "We rang the doorbell and nobody came to the door, guess you didn't hear it, or your bell is broken"
. However, I am not a lawyer
If they were on the street and taking pictures through the window, I think that is legal (visible to the public). They can also come up to your front door and ring the doorbell and if there is a window on the door, they can look through that. However, because they had to move the tarp out of the way, I really believe what they have done is illegal and you should consult a lawyer.
However, the exception would be if it is believed to be an emergency in the home.