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a man's home is stil the exception to a warrantless arrest, unless like you state, there is reason to believe that a crime is being committed or if your son was chased into your home during a hot pursuit. if they knocked for 90 mintues, it is apparent there was no danger. it appears you have a very serious 4th amendment violation.
you can contact your local ACLU and ask about consulting with one of their attorneys on the matter - the ACLU works on these matters. use this link to contact them