The Santa Clara DA's office has decided not to charge Ahmad Brooks with assault. You can read the details on the incident that led to the arrest here, but regardless, after further research into the case, District Attorney Jeff Rosen apparently figured that obtaining a conviction may be problematic.
That investigation turned up new evidence, including a May incident at a barbecue at Brooks' home in which Divens pushed Brooks to the ground, causing a two-inch cut on Brooks' leg. According to the DA report, the two had been "wrestling" and "shadow boxing" throughout the afternoon. No one called the police, Brooks tended to his wound and Divens remained at the party.
"I have reviewed the memo and agree with its conclusion," [District Attorney Jeff] Rosen said in a press release. "Cases are not always what they first appear. The value to a thorough and deliberate investigation is a more complete picture of the facts. We cannot prosecute this case because we cannot prove the crime beyond a reasonable doubt to 12 jurors. To file criminal charges when we do not believe we will obtain a conviction is wrong."
Will the Niners suspend him nonetheless for hitting his teammate in the head twice with a beer bottle (in this case, originally considered felony assault with a deadly weapon)? Doubtful. In a statement today, the team said, " ... we look forward to moving on from this situation and will have no further comment."
There is still a chance that Roger Goodell could suspend Brooks because of the outside linebacker's past history with legal issues, but we shall see.