One public defender may be handling as many 350 cases a year. In some states like New Orleans they may have as many as 1000 cases a year when they are only supposed to be working on up to 150, some attorneys spending as little as 7 minutes per case.
The system is overburdened so this is why many cases, as much as 95% end up in plea bargain and people wind up pleaing guilty for crimes they didn't commit.
This disproportionately affects the poor and they wind up with a criminal record when they've done nothing wrong.
40% of public defenders don't have investigators on staff.