In which case the prosecution should have realised he was a suicide risk and acted appropriately. They seemingly did not.
Come on. This prosecution may be unjust for other reasons, but it's just daft to claim that they should not have prosecuted him because he was depressed.
If someone is a suicide risk you watch them, and typically ensure they're not left alone.
Stick your straw man where the sun don't shine.
I don't think you're thinking this through. It's natural to be angry, but the DA didn't do anything wrong in relation to his depression, even if the prosecution was unjust for other reasons.
See http://www.mind.org.uk/mental_health_a-z/8042_mental_health_... for an explanation of (in the UK, at least) the rights for those with mental health issues in prosecutorial circumstances.
2) All of that requires the consent of the person involved. Do you think AS would have suddenly decided to accept support because the DA prosecuting his case offered it? If his family and friends couldn't stop his suicide, you think the DA could have done so?
3) Are you sure it is typically the responsibility of the DA to sort that stuff out in the US?