The criminal laws define certain words which often differ with a laymens definition. In California a accomplice is often charged with others in criminal prosecutions. As a Torrance Criminal Defense Attorney I have represented many people charged as an accomplice, here is what the law says:
An accomplice is defined as one who is liable to prosecution for the identical offense charged against the defendant. This definition includes all principals in a criminal act (i.e., “[a]ll persons concerned in the commission of a crime”, see for example Penal Code 31, but does not include accessories (i.e., “[e]very person who, after a felony has been committed, harbors, conceals or aids a principal in such felony”, see Penal Code 32. Whether a person is an accomplice is a question of fact for the jury unless there is no dispute as to either the facts or the inferences to be drawn therefrom.
The fact that “the witness was prosecuted for the same offense as defendant does not alone establish her to be an accomplice [as a matter of law].” Criminal liability as a principal attaches to those who aid in the commission of a crime only if they also share in the criminal intent , see also Pinell v. Superior Court (1965) 232 Cal. App.2d 284, 287) or, in the language of penal code section 31, abet the crime. Thus a person is an accomplice only if at the time she acted she had “guilty knowledge and intent with regard to the commission of the crime.” (People v. Duncan (1960) 53 Cal.2d 803, 816.)
For example, in (People v. Tewksbury (1976) 15 Cal.3d 953, 967, The defendant was not necessarily an accomplice merely because she was held to answer for the same crimes as defendants and then granted immunity. Nor did she necessarily become an accomplice if it be deemed that she aided in the commission of the crimes.
The importance of an accomplice is particularly at issue in cases where the accomplice testifies against others. In these cases, the law requires corroboration, such as other evidence that the testimony is reliable.