
Quoting
cdwjava
The officer in the field is in no position evaluate the status of someone's "affirmative defense". Suspects say things like, "I was with my mother!" all the time. It may be incumbent upon the officer to look into that, but it does NOT mean that he has to let the guy go until he has had a chance to check out the alibi. He can hook the suspect then later look into the alibi. if the alibi is solid, he can then have the suspect released.
And, of course, alibi witnesses can lie or be unreliable.
An "affirmative defense" can be anything. And the police are not going to be strapped to avoid arresting someone simply because he claims he didn't do it and might be able to prove it. If there is sufficient probable cause to make the arrest, they can.
- Carl