From New Scientist (30 April 2011), we learn that in a recent evolutionary psychology study, “Deliberate inaction judged as immoral as wrong action”:
An actor whose hesitancy to act led to the death was seen as less immoral than an actor whose direct actions led to the death. But the students judged deliberate inaction that led to the fatality as equally immoral as direct action that caused the death.
In fact, in many jurisdictions, if a person has a professional duty of care, it is not a matter of opinion; failing to report child abuse, for example, can lead to criminal charges. It’s good to know that students sense why those laws exist.