in (someone or something's) custody
Detained by someone or something; in legal custody of someone or something. Of course I'm panicking, I just got a phone call that said my son is in police custody! Mr. Foster, you have been found guilty by a unanimous jury. I place you in the state's custody to await sentencing.
in custody (of someone or something)
and in someone's or something's custodybeing kept guarded by legal authorities. The suspect was in the sheriff's custody awaiting a trial. The prisoner is in the custody of the state. The police have two suspects in custody.