If I came home and my 17 year old daughter was having sex with her 19 year old (ed:th) boyfriend on the couch, accoring to the letter of the law I could shoot him.
Are you certain about that? According to my lay reading, you may indeed use deadly force to prevent the act. Can you shoot after the crime has been committed for the purpose of what would in effect constitute punishing the perpetrator? Better check into that. Maybe there has been precedent...
13-411. Justification; use of force in crime prevention; applicability
A. A person is justified in threatening or using both physical force and deadly physical force against another if and to the extent the person reasonably believes that physical force or deadly physical force is immediately necessary to prevent the other’s commission of arson of an occupied structure under section 13-1704, burglary in the second or first degree under section 13-1507 or 13-1508, kidnapping under section 13-1304, manslaughter under section 13-1103, second or first degree murder under section 13-1104 or 13-1105, sexual conduct with a minor under section 13-1405, sexual assault under section 13-1406, child molestation under section 13-1410, armed robbery under section 13-1904 or aggravated assault under section 13-1204, subsection A, paragraphs 1 and 2.