Since a getaway vehicle often requires a getaway driver, this additional co-defendant creates problems in itself. First, having a second perpetrator involved creates yet another inchoate offence that the prosecutor can use in an indictment: conspiracy. Also, a co-conspirator may cooperate with police, either intentionally by 'turning state's evidence' by way of a plea bargain, or inadvertently by giving away information to persons outside the conspiracy. If the driver, who may have parked some distance away, unknowingly drives past the scene of the crime, the getaway vehicle itself may identify the occupants to the crime victim and police. This is especially true if the vehicle has unique markings or is an unusual model. Without a driver, the perpetrator may make errors due to the stress associated with the crime, or lack of ability to multi-task (such as leaving the car keys at the scene of the crime); a murderer needs to "think strategically" to get away with murder—to "mislead police, stage crime scenes and destroy evidence."