。
The lawyer had doubts about his innocence.
Literal
Lawyer [topic-は] his innocence [in-に] doubt [obj-を] held.
疑問を持つ ('hold doubt, have questions') is the standard idiom for having doubts — Japanese uses 持つ ('hold') for many mental states that English handles with 'have': 希望を持つ (have hope), 自信を持つ (have confidence), 興味を持つ (have interest). に marks the thing about which one has doubts.