In preparing for criminal trial, police are frequently interviewed and rehearsed by prosecutors. Words, phrases, and recollections that might lead to troublesome cross-examination are excised, and other terminologies more favorable to the prosecution are substituted. Potential police witnesses are warned about inconsistencies and incongruities in their testimony and reports. In the end, the actual content of the officer’s sworn testimony may be substantially changed from his or her original recollection. Is this legal? Is this ethical? When does the rehearsal and preparation of a witness so substantially change the way an incident is portrayed that it becomes perjury?