In a fair judicial system, they will protect you if you have nothing to be guilty of. Also on the other hand, if they have a judicial warrent for your phone, then it'll be a crime to not produce it, or destroy it.

In a country with a lawless system, and this is a real story btw that happened to my friend: The ones with deleted whatsapp conversation or "lost phones" recived 10+ years extra while his peers who committed the same exact crime in the same group but opened their phones recieved 2 years. I myself have read the prosecution case papers where the judge added the crime of them deleting whatsapp conversations, and formatting or destroying phones.