Legal Question in Criminal Law in California

Yes, unless the court has ordered you not to and/or the jail has placed restrictions on who can visit or communicate with your ex. But be careful what you say. The authorities might read your letters to one another and/or listen in on your conversations, whether in person or by phone. That means anything he tells you could end up being used as evidence against him. If you say something the prosecutor finds helpful, you could be subpoenaed and questioned about it at trial.