Going to answer a knock on your door only to see the police outside can put you in a difficult situation. Do you have to open it to them, or can you just pretend you are not home?
The answer is that it depends.
If the police have a search warrant or arrest warrant
If the police have a warrant to search the premises or one to arrest you, then you may just as well open the door as they will come in anyway. At the very least, it will spare you the cost of repairs if they decide to break down the door.
You should check that the warrant exists and is correct first. Ask the officers to push it under the door or hold it up to a window so you can check all the details are correct and that a judge has signed it.
If the police do not have a warrant
In this case, it is entirely up to you whether you open the door and whether you allow the police officers to enter. They cannot do so without your permission bar exceptional circumstances, such as if they honestly believe they have to break in to prevent someone from getting hurt or to prevent someone from destroying evidence.
If nothing special is happening, then it’s best to just keep them out. Beware, though, as they may try to trick you into giving them permission – by phrasing the question of whether they can come in a way that catches you off guard.
Whether they enter or not, you do not have to answer their questions. If the police arrest you after entering your house, getting legal help to determine whether they acted within the law could help you beat the charges.