The Day the Earth Stood Still (2008)

Continuity mistake: When the scientists are walking through the fog towards the sphere shortly after it has landed in Central Park, we see them walk through many lines of trees before reaching the sphere. Camera cuts to a different angle, when the fog has all cleared and we briefly see behind the scientists and it only shows one line of small trees quite a bit away, not the lines of trees they were walking through before.

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?