This is a complicated question. You don't have to retreat in your home. If someone is outside your home you should call 911. You could be charged with a crime if their not inside the house or if they're retreating.
My answers are intended only as general legal advice and are not intended to create an attorney-client relationship. There is no substitute for a full consultation with a local experienced criminal defense attorney. For more answers based on my 19 years of experience visit my website, www.austincriminaldefenseattorney.com