"Duty of care" is a legal obligation that occurs when one person is responsible for the care of another, usually as a result of their occupation but not always. The word "care," though, has a broad meaning. A good way to think of it is "duty to care about how my actions might harm another."
"Duty of care" is actually pretty broad in terms of what it relates to. Defining it is made more difficult because, in the United States, each state is responsible for creating it's own definition (there is no Federal law regarding this.) Therefore, depending on which state you are in the requirements under "duty of care" will be different.
In general, for DOC to exist it would have to be proven that the "caregiver" had an obligation to an individual. This doesn't just mean in a medical sense, though that is the easiest to understand:
- If I am making a product I have a responsibility to be fairly certain that my product isn't going to harm anyone when I start to sell it,
- If I have a piece of land and invite people onto it, I need to clean up any bear-traps I put out before they arrive,
- In business, DOC care mean having faith that officers of a corporation are acting in the best interests of the shareholders.
Once a person has proven that a DOC relationship exists, it would have to be proven that the person in question violated that relationship. This is where it really matters what state you're in. In general, though, there is one common concept: Foreseeability--could the "caregiver" have reasonable figured out that their action was going to cause someone harm?
For example, if I am building a home and I use crackers instead of wood for the floors, should I have been able to figure out that this was going to harm someone before I did it? Of course, it usually isn't that easy : ) Hindsight is always 20/20, as they say. If I leave a candy-bar wrapper on the sidewalk and somehow somebody slips on it, could I really have seen that coming?
Other states, such as California, have a much stricter criteria that includes some of the these ideas:
- What were the odds that someone would be harmed? Was it a "1 in a million" kind of thing?
- How "close" were my actions to the outcome? If I left a banana peel in my driveway, for example, and someone picked it up and put on the sidewalk, am I liable for that?
- Could the person who was harmed have reasonably done things differently and avoided the outcome?
- Does imposing a DOC in a particular case cause an undo amount of expense on a community to prevent future, similar cases?
In short, "not being careful" is a great way to have a breach of DOC, but you'd have to establish that DOC existed in the first place. Also, someone, such as a doctor, can be very careful and still harm a person accidently. A business that makes a new toy might have had no idea that the paint contained lead. Should it have checked every toy it made for lead in the paint? What is reasonable?
As you can see, DOC is a complicated issue that varies a good deal from place to place. And while "care" is definitely part of it, that's only the tip of the iceberg.