I disagree. I think if you make officers individually responsible, you will paralyze them. In this case instead of the wrong person arrested for the murder, nobody would be arrested and the case would go unsolved. My suggestion would be to treat it like an air crash investigation. An independent body produces a public report on each incident, with the power to make changes to procedures or training, or even recommend changes to the law, with no blame or punishment, and the full co-operation of all parties. Maybe it's less satisfying, but for air travel safety this approach is incredibly effective, and it seems like it could be for policing.