Blackstone's Police Investigators' Manual 2018 Is The Only Official Study Guides For The National Investigators' Exam (nie), Which Is Taken As Part Of Phase 1 Of The Initial Crime Investigators' Development Programme. Together With Blackstone's Police Investigators' Workbook 2018, They Are The Only Texts Endorsed By The College Of Policing And Have Established Themselves As The Definitive Reference Source For All Who Are Involved In Criminal Investigation.