This article caught my eye, as it illustrates a way authorities can really make the process of investigation and trial into a punishment that probably never would be implemented by a jury. More or less, 40 states allow the state to recover legal fees paid on behalf of a poor defendant, and those who are not able to repay face various sanctions like losing drivers' licenses and the ability to register a vehicle.
And since a person who cannot legally drive really cannot legally work, a person who is accused has a choice between debtor's prison and a life of criminality. I do believe that Charles Dickens wrote something about that, as did Victor Hugo. We may be creating career criminals by our approach to legal aid for the poor.
Worse yet, for crimes less than (and maybe including) murder, the police do not do a thorough job of investigating. A 2017 Star-Tribune report found that only 20% of rape allegations got a good basic investigation, but 26% of them were referred to the prosecutor. One in four people whose cases are referred to a prosecutor are referred on the basis of a paper-thin investigation.
Now let's think of this in light of investigators' responsibilities from Brady v. Maryland and Kyles v. Whitley--to seek out and provide exculpatory (exonerating) evidence. Probably the easiest way to avoid these responsibilities is to never collect the evidence in the first place. "Oopsie. We put our guys with forensics degrees out on traffic patrol, so they really don't have time to interview rape victims and potential witnesses. Sorry about that!"
Wealthy defendants can get around this by hiring their own investigators to do the investigations the police do not do. The rest of us? Not so much. Again, it's a choice between a ruinous plea and ruinous debt.
So what should be done? My take is that the government needs to do (with private help) what businesses do; audits. Something along the lines of ISO9001, really, where an auditor would come by once a year, take a number of files from the police and the prosecutor's office, and examine them to see if basic standards are met. If they're not, corrective action (like taking Officer Friendly off traffic patrol and having him do investigations) would be required, and the next audit would use a much larger sample.
Ideally, any government auditors (who often get stymied, if my reading of the federal government is accurate) would be augmented by conscientious policemen, prosecutors, judges, and defense attorneys, pushing back at inadequate investigations by saying "This case was not investigated per basic standards--let's start from the beginning."