An Author Needs to Know
About the Police and the Law
What is a crime?
What is a crime?
A crime is a misdemeanor or a felony. Violations and infractions are not defined as crimes, and as such generally result in citations (parking or speeding tickets) and fines. There are no common law crimes, meaning your character can't be arrested for bad behavior unless said behavior breaks a written law, such as lewd behavior in public or disorderly conduct. Examples of non-arrestable and non-finable bad behavior might include emotional abuse, cruelty, or cheating.
Only the legislature can create laws (criminal statutes). The courts and the police cannot create a new crime. Oftentimes in court the judge will explain the law associated with the crime to the jury and add that although the jury may not agree with the law, say a marijuana charge, it is their duty to uphold the laws of the state as they are written today.
You can only be convicted if the state/commonwealth can prove you committed each and every element of the crime. That's important. Each and every element. Failure to do so will result in an acquittal.
According to wisegeek.org:
For example intent, also known as mens rea or “guilty mind,” requires someone to intend to commit a crime, and to have the mental capacity to have intent. For example, someone who plans to commit a robbery clearly meets the condition of intent. If the robber hits and kills a pedestrian with the car on the way to the robbery, however, the robber cannot be charged with murder because he or she did not intend to kill the pedestrian. The pedestrian is still dead, of course, and the robber will be liable for manslaughter."