I think your brother's duty in this case is not to his client, but to the rule of law: he's there not to defend his client's horrible actions, but rather to ensure that the punishment is assigned and carried out fairly, legally, justly, in line with the Constitution, and doesn't become the public stoning / lynch mob we all maybe would prefer to see while our blood's still boiling.

Tips from a lifer PD, to a newbie, grabbed from elsewhere:

You are a criminal defense lawyer. You are not a social worker. You are not a teacher. You are not a life coach. Don't act like those. You CANNOT get emotionally involved in your cases. That's death. Because it's not your life. You didn't arrest the person, etc. Stick to your defined role.

You cannot live your client's lives for them. For the most part they're adults who have made bad choices. I work in NYC, and I don't want to hear the institutional racism bullshit for why my client committed armed robbery. Yes, there's racism in a lot of petty drug arrests, stop and frisk, etc. But those aren't the hard cases. Commiting a crime is a a choice he made. That's OK, because it wasn't my choice. I just have to clean up his crap. I will refer to social workers, etc., but I'm his lawyer. I need to act like it. I don't mean be standoffish or an ass, but I mean be friendly but professional. The moment you start commiserating with him about his fucked up family life, you're sucked in and it's over. You may very well feel that way, and that's fine, but the cold reality is that it's not you're life and you're not responsible for him sitting in front of you. If he's an adult, he's responsible for his own life. And that's something a lot of our clients can't grasp.

Don't take the job home. The moment you walk out of the office, you have to make a conscious, voluntary decision to focus on your life and what you want to do, and not on the 17 year old kid who shot his buddy and is in jail on $100,000 bail. Because when you bring that home, you're just traded your life for his. It took me about 2 years before I was really able to leave things at the office. But again, it's a conscious effort. Obviously, if you're on trial or something, that consumes your life.

Pick your battles. There are zillions of awful decisions by judges, lying ADAs, deceitful clients, and general malfeasance. You have to let 90% of it go. Why? Because doing something about it won't get that judge's decision changed. Save your efforts for the issues that both matter and you have a chance of prevailing on. I've seen some awful decisions, and the first question is "who is the judge hearing motions today?" That colors my decision on what to do. And regardless of the motion judge, if it's a henious decision but I know I will lose the fight, I don't fight. I don't have the time or the energy. You'll learn that not everything is as big an injustice as it first seems.