The Day the Earth Stood Still (2008)

Factual error: As Klaatu is walking down the train platform at Newark Penn Station, in the background you can see signs that say "VIA". VIA is the national railway of Canada and does not have a presence in New Jersey. This scene was filmed in Canada, as evidenced by the signs on the platform and the 1950s style streamlined passenger cars on the track. Neither Amtrak nor NJ Transit uses those type of cars in their trains.

Klaatu: If the Earth dies, you die. If the human race dies, the Earth survives.

Trivia: When Klaatu is shown on the tv as an escaped convict, the phone number shown to call to report him is not the usual 1-800-555 number, rather it is 1-800-472-0391 which is the Alaska Weather Information Hotline.

Question: If Klaatu chooses to save the policeman that he injures/kills, and seemingly has the power to do this as many times as he wishes, why does he let the man using the Polygraph die?