If a person has been criminally arrested, his family and friends can't see him in person, and only lawyers can go to the detention center to see him. You should ask a lawyer to meet him in time, interview him, understand the case, provide legal help, determine whether it is lighter or mitigated, whether it is in line with the crime, strive for a lighter treatment, and safeguard his legitimate rights and interests.
Article 39 of the Criminal Procedure Law stipulates that defense lawyers can meet and correspond with criminal suspects and defendants in custody. Other defenders, with the permission of the people's courts and people's procuratorates, may also meet and correspond with criminal suspects and defendants in custody.