Instead of forcing people to give their mobiles, why not use the "innocent until proven guilty" age-old adage?
They aren't forcing people to give up their mobiles, merely saying that if a victim chooses not to, they are denying the police useful evidence. In the absence of other evidence, there's a risk that prosecutions won't go ahead.
The reason this is an issue at all is the presumption of innocence. The accused is presumed innocent and without evidence (which may or may not be on the phone) there is nothing the police or the courts can do.
They aren't forcing people to give up their mobiles, merely saying that if a victim chooses not to, they are denying the police useful evidence. In the absence of other evidence, there's a risk that prosecutions won't go ahead.
The reason this is an issue at all is the presumption of innocence. The accused is presumed innocent and without evidence (which may or may not be on the phone) there is nothing the police or the courts can do.