Negligence is one of two things: Either (1) the failure to do something that a reasonable man, guided upon those considerations which ordinarily regulate the conduct of human affairs, would do, or (2) doing something that reasonable man would not do. The law has evolved very slowly over time and so the "reasonable man" concept is burned into the legal world. However, we'll call him or her the 'reasonable person'.
A person causing an injury is liable if they either failed to do that which a reasonable person would have done, or did something that a person taking reasonable precautions would not have done. This is basic negligence law.
Theoretically, then, there is a uniform standard, that of the 'reasonable person' against which all human conduct is judged in determining negligence. It does not matter if the person being judged is not a brain surgeon. We all go out into the same world each day and we are all judged - theoretically and legally - by the same standard. The standard is that of a reasonably intelligent person "who makes prudence a guide to his/her conduct."
Individual courts and jurors are not to superimpose their own personal standards on a given scenario. Instead, the correct standard in which to judge whether a person's conduct rises to the level of negligence is that of the reasonable person.
So, when negligence cases go before a jury, the judge does not instruct the jurors to ask themselves if "they would have acted differently". Instead, the standard, the measuring stick, is "how would the reasonable person have acted." Unfortunately there is no one person who can be dragged in off the street, the model "reasonable person" to whom the jurors can submit the facts and get a clear answer. Perhaps this is why the U.S. Constitution establishes the right to a jury of one's "peers" to listen to the facts, and then to figure out amongst themselves whether the defendant acted as the mythical reasonable person.
As the great U.S. Supreme Court Judge Potter Stewart said about a different subject "I know it when I see it". So, allowing a jury of people in the community to determine whether the 'reasonable person' standard has been violated in any given case is the legal system that we have. Jurors are expected to know negligence when they see it.
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