In U.S. common law, there is no general duty to come to the rescue of another.<1> Generally, a person cannot be held liable for doing nothing while another person is in peril.<2><3> However, such a duty may arise in two situations:
A duty to rescue arises where a person creates a hazardous situation. If another person then falls into peril because of this hazardous situation, the creator of the hazard — who may not necessarily have been a negligent tortfeasor — has a duty to rescue the individual in peril.<4>
Such a duty also arises where a "special relationship" exists. For example:
Emergency workers (police, firefighters, EMTs, etc.) have a general duty to rescue the public within the scope of their employment, but not a duty to specific individuals.<5>
Parents have a duty to rescue their minor children. This duty also applies to those acting in loco parentis, such as schools or babysitters.<6>
Common carriers have a duty to rescue their patrons.<7>
Employers have an obligation to rescue employees, under an implied contract theory.<8>
Property owners have a duty to rescue invitees from all dangers on the property.
Spouses have a duty to rescue each other in all U.S. jurisdictions.<9>
Contrary to common law, eight states have laws requiring people to help strangers in peril: Florida, Massachusetts, Minnesota, Ohio, Rhode Island, Vermont, Washington, and Wisconsin. These laws are also referred to as Good Samaritan laws, despite their difference from laws of the same name that protect individuals that try to help another person.<1> These laws are rarely applied, and are generally ignored by citizens and lawmakers.<1>
Where a duty to rescue arises, the rescuer must generally act with reasonable care, and can be held liable for injuries caused by a reckless rescue attempt. However, many states have limited or removed liability from rescuers in such circumstances, particularly where the rescuer is an emergency worker. Furthermore, the rescuer need not endanger himself in conducting the rescue.
http://en.wikipedia.org/wiki/Duty_to_rescue