For DougR:

Arizona Senate Bill S.B. 1070, ENACTED:

ARTICLE 8. ENFORCEMENT OF IMMIGRATION LAWS

A. …

B. FOR ANY LAWFUL CONTACT MADE BY A LAW ENFORCEMENT OFFICIAL OR AGENCY OF THIS STATE OR A COUNTY, CITY, TOWN OR OTHER POLITICAL SUBDIVISION OF THIS STATE WHERE REASONABLE SUSPICION EXISTS THAT THE PERSON IS AN ALIEN WHO IS UNLAWFULLY PRESENT IN THE UNITED STATES, A REASONABLE ATTEMPT SHALL BE MADE, WHEN PRACTICABLE, TO DETERMINE THE IMMIGRATION STATUS OF THE PERSON.

"Lawful contact" undoubtedly includes asking (presumed innocent) witnesses to an antisocial act or other event in which a crime may have occurred for their observations of events they may have witnessed. In many situations, the police have the authority to detain "for questioning" persons NOT SUSPECTED OF PARTICIPATION IN ANY UNLAWFUL ACT. Hesitation in responding, while it might be due to simply "not wanting to get involved" or fear of retaliation by someone who might be accused of an offence, could be considered by the officer, and is NOT EXCLUDED, as a cause for "reasonable suspicion," in which case the officer would be bound, by this law, to attempt to determine the legality of the person's presence in the US.

It is NOT, under the definitions and terms stated by this law, necessary that the person who's lawful presence MUST be questioned must be suspected (reasonable cause or otherwise) of ANY VIOLATION OF ANY LAW.

John