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 the officer has come to your home because he/she may be conducting an investigation or may have information regarding problems or concerns in your neighborhood or the safety of your family or property.