This issue comes up under various considerations, one important being your right to a Speedy Trial. As a general rule, however, if you are placed in custody, your "speedy trial" rights require the prosecutor to decide within 72 hours which charges, if any, will be filed.  Many states adhere to this 72 hour limit, but other states, such as California, go further and require that the decision be made within 48 hours after someone is taken into custody. You need to get your friend help asap. Speak with a lawyer.