conspiracy n. when people work together by agreement to commit an illegal act. A conspiracy may exist when the parties use legal means to accomplish an illegal result, or to use illegal means to achieve something that in itself is lawful. To prove a conspiracy those involved must have agreed to the plan before all the actions have been taken, or it is just a series of independent illegal acts. A conspiracy can be criminal for planning and carrying out illegal activities, or give rise to a civil lawsuit for damages by someone injured by the conspiracy. Thus, a scheme by a group of salesmen to sell used automobiles as new, could be prosecuted as a crime of fraud and conspiracy, and also allow a purchaser of an auto to sue for damages for the fraud and conspiracy. (See: conspirator)