One type of good Samaritan law establishes a duty to rescue. This kind of law says people must rescue a stranger who needs help, if it is easy to do so. For instance, a person might have a duty to call out to someone who is about to step into the street and get hit by a car.

Professor Mikhail says the punishment for failing to rescue might be a fine or perhaps jail time. But few states have such laws, he says, pointing out that this kind of law raises questions.

JOHN MIKHAIL: "How much aid are you supposed to render someone who's in need? Why doesn't that apply to the easy case of sending fifty dollars to Oxfam to save a life around the world, or at least someone here at home who's starving and who could easily have harm prevented by your small effort?"

The second type of good Samaritan law protects people who choose to help others.

JOHN MIKHAIL: "Imagine the situation of a doctor on an airplane, or someone calls for a doctor. One type of law that's been pretty sensibly passed is a law that would protect the doctor who offers help in that kind of situation from lawsuits, unless they are grossly negligent."

All fifty states have some kind of law that protects good Samaritans in a medical emergency. In July, New York became the latest state to pass a law protecting people who call for help when someone has a drug overdose.

In these cases, the witnesses may not want to call emergency services because they are afraid of getting arrested for having drugs. But New York and a few other states have decided that people who act as good Samaritans in these situations should not have to worry about getting arrested.