"Turning" this type of "evidence" means giving testimony to implicate accomplices
Turning to paragraph 48, we find that 'opium prepared for smoking' is the only 
... 'prepared opium, subject to duty of twelve dollars per pound,' can mean only .... 
an accomplice, who had turned state's evidence, to give testimony as to the... [DOC] [TLE] Ex Post Facto Limitations of Changes in Evidentiary Law: Repeal of ... [PAR] based on an accomplice's testimony unless the testimony was corrobo- rated by 
... panying text (discussing the two fundamental types of ex post facto law).