When conducting a criminal investigation, law enforcement personnel interview as many people as they can in the hopes that the more pieces of the puzzle they get, the more of that puzzle they can put together. Witness interviews or interrogations of suspects both involve a great deal of time spent checking the veracity or accuracy of the statements. Especially in cases involving conflicting accounts of the event in question, it is essential that the investigator(s) cross-check information so that any inconsistencies or gaps can be identified. Failure to do so will weaken the prosecution's case. Cross-checking information invariably involves reinterviewing witnesses, suspects, and other individuals somehow connected to the case.
Procedures for the follow-up interviews, therefore, consist of going over the initial witness or suspect statements multiple times to see if the statement changes in any way -- a possible sign of deception or faulty memory. In addition, investigators will pose questions in different ways to ensure consistency of the statement, and will build upon the initial interview with additional information attained through the investigation since the initial meeting. Contradictory statements from different witnesses or suspects have to be resolved before the case can go to court, lest defense attorneys use those inconsistencies to weaken the prosecution's case.