It is important that you make sure the person at the door is a law enforcement officer.  Once the officer has provided sufficient identification, he or she may ask permission to enter your home.  Unless the officer has a warrant, you have the right to refuse the officer access to your home.  Nevertheless, you should politely ask the officer why he has come to your home because he may be conducting an investigation or may have information regarding problems or concerns in your neighborhood or the safety of your family or property.