It seems to be routine for rape complainants to have to hand over their phone and have their messages scrutinized, as a pre-requisite to proceeding with an investigation. That is a form of government blackmail.
Of course. But you shouldn't have to spill your guts about your entire life (I understand that young folk nowadays life their lives in Instagram selfies).
And more to the point, the first step for the policemen investigating a rape complaint should be to investigate the complaint, not the complainant. If the investigation of the complaint raises questions about the complainant, then there might be grounds for seizing the complainant's device. But they can't make device seizure a pre-requisite for doing their job.
Not the police!
Which government? What level? My god, who told you this thing? For what other crimes is this policy enforced?