But to be clear, cops can't just go to a judge and say "we suspect them in a kidnapping and we want to search their house." They need specific evidence to convince a judge to issue the warrant and the warrant must be fairly specific regarding what they are looking for. Evidence collected outside the scope of the warrant can't be used at trial.Suspects in a kidnapping. Charges can be upgraded later.
A consentual warrant is far more dangerous because they can seize anything they find even it was not something they were looking for. I personally would never consent to a search for any reason no matter how innocent I were.