I don't know any constitution or law that forbids the police from entering peoples home if there was a serious crime. (A warrant Btw. landlords also may do thi

I don't know any constitution or law that forbids the police from entering peoples home if there was a serious crime. (A warrant Btw. landlords also may do this under special circumstances, as well as a firemen. But the default is, that your home is sacred and the doors my not breached. Just as the default for communication should be, that it is private. If there is a suspect, the police may hack their computers with a warrant, but they may not hack all of our computers(by implementing backdoors), because it is more comfortable for them.