As you know, prosecutors have vast discretion to decide whether to charge someone with a crime. Prosecutorial discretion can be a dangerous thing, but it is usually thought to be needed for the proper functioning of our criminal justice system.
As explained in one of the few texts available on prosecutorial ethics, "[t]he decision of what criminal charges to bring against an accused provides perhaps the best example of the vast discretion held by the prosecutor's office. ... If the prosecutor determines that no charges are warranted, neither a private citizen nor a judge may compel the prosecutor to commence criminal proceedings. See, R. Michael Cassidy, Prosecutorial Ethics, Ed. ed. 11 (2013).
For this reason, it is surprising to read that a District Judge in Denver has has ordered the Denver district attorney to appear in court today to explain why a sheriff’s deputy wasn’t prosecuted for slamming an inmate, who was in handcuffs and waist chains at the time, into a courtroom window frame during a court proceeding. The incident was caught on camera, as seen below. As you can see in the video, the defendant is addressing the judge calmly (about something related to the investigation) when the deputy attacks him and starts yelling "don't turn on me!"
According to an article in The Denver Post, here, the District Attorney has been criticized by various community groups, including the NAACP and Colorado Latino Forum, because he rarely prosecutes police or sheriff's deputies accused of excessive force.
The decision by a judge to question prosecutorial discretion is rare and its implication can be important. I am very interested to see what comes of this.
Here is an UPDATE.