Literally anything that protects people from the law will protect criminals and terrorists too.

Fourth amendment? A terrorist might have a bomb in their trunk that the police aren't allowed to search.

Jury trial? A psychopathic murder might charm the jury into thinking they're not guilty and get released.

Prove guilt beyond a reasonable doubt? What if the person is actually a horrible criminal but there's reasonable doubt?

We have these protections not because they save ordinary people while still letting the government do everything possible to catch criminals, but because we think it's worth reducing the government's ability to catch criminals in exchange for fewer abuses of non-criminals.