BK - The interrogation

Just finished part 3 today. Overall I was fairly impressed by the fairness and thoroughness of Dmitri's Karamazov's interrogation in part 3, but there were one or two things I thought were odd. I thought it was odd that one of the interrogators told Dmitri of an important material fact they found at the crime scene while they were taking his statement. Later on, they told him that they were obliged to answer and questions Dmitri asked. In the UK the police are obliged to hand over any evidence they find to the defence, but surely not during the taking of statement. Another thing I found odd was that after the interrogators had questioned Dmitri, they proceeded to question the other witnesses in front of Dmitri. Dmitri was allowed to question them or challenge them. So, is this some combined interrogation and trial? If so, is the defendant expected to conduct his own defence without help from a lawyer? Maybe I shall find out in part 4.