Human beings leave behind DNA wherever we go. We shed skin. We sneeze out DNA-containing droplets. We shed hairs. We can't avoid it.
Traditionally, search warrants only went one direction. A crime was committed or suspected, and the police would investigate. Witnesses would be contacted. A theory would be developed. When the police had probable cause to search for evidence, they got a search warrant and searched.
When we think about cases where a person has refused a chemical test in drunk driving cases, we may think of a belligerent individual who may be so impaired that they don’t understand the legal consequences of their choice. We certainly don’t think that a person may be charged with a crime even though they were following the law.
If an Iowa resident is suspected of committing a crime, police may search his or her home or seize property if it is evidence of that crime. However, there are limits to how far the government may go to collect this evidence. The Fourth Amendment to the Constitution says that only reasonable searches and seizures may be conducted. For instance, a search may generally not be conducted without probable cause.