Adjective
scared stiff (not comparable)
(literally) scared to the point of being unable to move, or (figuratively) very scared. [from 1890s]
He was scared stiff, like a deer in the headlights, by the vampire walking toward him.
He’s either scared stiff by a flying car or incapable of getting out of a burning house. Source: Internet
On advice, some presidential advisers seem to be scared stiff to give the right advice since they want to protect their jobs. Source: Internet