Does negligence depend on who was doing what?

Negligence is entirely dependent on who was doing what. Negligence is a legal concept that is used to determine fault. It is based on the principle that a duty of care is owed. If that duty of care is breached, then legal negligence may exist and the person who was negligent may be liable for any injury he or she causes.  

How does personal injury law define a “duty of care”?

Every person has a legal duty to act with a reasonable standard of care. The definition of a reasonable standard of care varies based on the level of responsibility carried by the person in question. Some examples include the following:

• The average person is simply held to a hypothetical reasonable person standard. In other words, if you are driving down the street, you are expected to act with the same level of care that the average reasonable person would. Your age, education level, background and emotional state aren't taken into consideration. You are simply compared with a hypothetical reasonable person.
• Professionals are held to a professional standard of care. In other words, a physician will be held to the standard of a reasonable physician in his field. A lawyer will be held to the standard of a reasonable lawyer.
• Children are held to a standard of care based on what a reasonable child of their age would do. For example, a four year old will not be expected to know and understand how to behave responsibly, while a 15 year old might. 
• Property owners are held to a standard of care that they owe to visitors based on who the visitor is. Those who run a store and invite customers to that store typically owe the customers the highest duty of care, while property owners owe the lowest duty of care to trespassers. 

There are numerous situations where the concept of legal negligence becomes important, and the definition of negligence may be different in each of those cases. If you believe you have been the victim of someone's careless actions, you should strongly consider speaking with a lawyer to find out if you have a potential claim for damages.