For my story, I was thinking the main character, a cop, can save a kidnap victim cause even though he doesn't have a warrant to go in, he cares more about the victim's life.

Of course the evidence of a kidnapping on his part is now tainted as fruit of the poisonous tree, cause he didn't have a warrant. However, can the victim still be used as evidence, or could she still bring charges?

Or would the prosecutor tell her "sorry, you were discovered by the police illegally, so you are now tainted, and cannot testify against your kidnappers, even you want to bring charges yourself"?