In the United States Supreme Court’s most recent decision of Kentucky v. King, No. 09-1272 , the Supreme Court has further eroded the value of the 4th Amendment. The opinion allows for police to enter a person’s home without a warrant based on the suspicion that there is criminal activity going on. In the Kentucky case the officers followed a suspected drug dealer into a home and then knocked on the door. Upon knocking the police heard what they believed was movement and destruction of potentian evidence. The Police then entered without a warrant and saw drugs in plain sight. The US Supreme Court said this was ok because of exigent circumstances.
Drug cases are often times very much about police procedure and following proper 4th amendment searches. For more information see: http://www.legalmann.com/CriminalDefense/DrugCharges.aspx