St. Louis County prosecutors may have misled the grand jury investigating the police shooting of Michael Brown into believing that Ferguson, Missouri, police officer Darren Wilson was justified in shooting Brown merely because the unarmed black 18-year-old fled from the officer, according to a review of the grand jury documents by MSNBC's Lawrence O'Donnell.

Before Wilson testified to the grand jury on September 16, prosecutors gave grand jurors an outdated statute that said police officers can shoot a suspect that's simply fleeing. This statute was deemed unconstitutional by the US Supreme Court in 1985; the court ruled that a fleeing suspect must, at least in a police officer's reasonable view, pose a dangerous threat to someone or have committed a violent felony to justify a shooting.

Prosecutors, who had full control of the evidence presented to the grand jury, took more than two months to correct their mistake, O'Donnell said. The prosecutors on November 21 — just three days before the grand jury reached a decision — gave the correct standards to the grand jury. But as O'Donnell explained, the prosecutors didn't specify what exactly was wrong with the outdated statute — and they didn't even clearly say, after they were asked, to the grand jurors that Supreme Court rulings do indeed override Missouri law.

No one has disputed that Brown did, at one point, run from Wilson. The legal debate, based on eyewitness testimony, has always centered on whether Brown attempted to surrender during the final moments of his encounter with Wilson. If Brown did attempt to surrender, Wilson may have been on the wrong side of the law when he killed the teen.

But the prosecutors' mistake, as explained by O'Donnell, effectively bypasses that legal debate by potentially misleading grand jurors into thinking that Wilson was justified in shooting just because Brown fled.

As Vox's Amanda Taub explained, the legal bar for justified police shootings is already fairly low. Police officers only have to reasonably perceive that a suspect presents a threat, even if the threat isn't real. If prosecutors misleadingly lowered the bar even further, it's no wonder the grand jury didn't force Wilson to stand trial.