In a 5-4 decision, Supreme Court rules it was OK for DAs to withhold evidence

Sorry, typing on iPhone is hard. I meant laws of disclosure are taught at law school. The fact that you have to disclose evidence is something every single lawyer knows. If this was an obscure law or rule I would understand. But this is basic.

Why did he have to sue based on this guy not training his staff? The simple fact that the prosecutors violated the most basic of evidentiary law and he went to prison as result should be sufficient grounds for a judgement against the city/state whatever. I don't understand why he tied himself down to the training part? It's not like a lawyer would get up in court and argue that his clients didn't know they had to turn over evidence.

The fact that these lawyers should have been trained in the need for full disclosure of exculpatory material at the law school level in the abstract does not change that the subject is more complicated in the specific, or that additional training on the subject is obviously warranted.

To oversimplify things, U.S. governments on all levels have made it so that you can only sue them for very limited things and immunized themselves for most other things. You essentially have to show the act of someone in a position of power led to the harm suffered.

If, say, McDonald's has a rogue employee who decides to spit in every Quarter Pounder at a location, you can sue both the rogue employee and McDonald's.

If a government has a low-level employee who fails in his duty or actively violates his duty, you generally are not going to be able to sue the government except in certain limited circumstances. You can sue the individual employee, but that isn't going to get you much of anywhere since that individual employee likely has no money to speak of.

So one of the few theories the lawyer had available to him (it seems to me) was that the big boss of the prosecutor's office failed in his duty to train his staff.

^ K, I'll take your word for it.

No amount of training will overcome willful malfeasance, to paraphrase what one of the Justices said in the decision. No amount of "training" will make a dishonest person honest.

If it had been a training issue, then fine: sue the person responsible for training. But it wasn't. As such, the lawsuit was groundless.