Brown was released from prison in 2015 after 10 years on death row. But at the time, he was not declared innocent.
Friday morning, special prosecutor John Raley gave a report on Brown's case explaining what led to Brown's initial conviction and why he is innocent.
Raley said that the grand jury was abusive and offensive, with one woman being threatened with sexual assault in prison if she didn't tell grand jurors what they wanted to hear.
Another woman was threatened with having her children taken away and jailed for several weeks until she told the story that former Assistant Harris County District Attorney Dan Rizzo wanted her to tell.
Rizzo is accused of not presenting key evidence during Brown's murder trial.
Brown was convicted in 2005 based on the concealed evidence. He was released from prison after that key evidence was discovered.
Raley said the case against Brown had only continued to grow weaker.
"There is no evidence sufficient for a reasonable juror to find that he is guilty beyond a reasonable doubt, which is the legal definition of innocence. Alfred Dewayne Brown is innocent as a matter of law," Raley said.
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Brown was accused of killing veteran Houston police officer Charles Clark in 2003 during a robbery at a check cashing place. A store clerk, Alfredia Jones, also was killed.
Brown had always maintained that he wasn't at the scene.
"The thrust of the report is Alfred Dewayne Brown. The evidence shows that he was not present at the crime scene and therefore, is actually innocent of the charges against him. (He) could not have been guilty of the murder of Officer Clark. It had to have been someone else," Raley said.
"He knew he was actually innocent, we knew he was actually innocent, but for the district attorney of the county to finally acknowledged that, is just extraordinary for him," said Neal Manne, Brown's attorney.
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The Houston Police Officers' Union responded strongly to the district attorney's announcement.
"This is ridiculous. Anybody with common sense, any detective with one year of experience can tell that there's evidence out there to convict this person," said Ray Hunt, former president of the HPOU.
Hunt continued, saying that he was disgusted with Harris County District Attorney Kim Ogg. "You are a disgrace to Harris County in this decision that you made. You are a disgrace to her (Jones) family and you are disgrace to this man's (Clark) family and his wife. And I don't care who quotes me in saying that," Hunt continued.
Officer Clark's wife, Hilda, also spoke, saying that she tried to meet with Ogg several times, but never got anywhere.
"I feel like I am fighting the system. I should not have to fight the system to get my husband justice, and with her blessing, she's going to allow Alfred Brown to collect money from the state for killing my husband," Hilda Clark said. "All I'm asking is for the community to support us and back us up, that we go and have another trial."
"I want to tell the families of the victims that I understand their anger and their frustration, I can understand it directed at us, that happens," Ogg responded. "But it does no justice to your loved ones to have a wrongfully convicted person tainted by what a prosecutor did in this case."
Two other people were convicted in the case and remain in prison.
Dashan Vadell Glaspie was convicted of aggravated robbery as part of a plea agreement and is serving a 30-year sentence.
Elijah Dwayne Joubert was convicted of capital murder and sentenced to death. He remains on death row.
It is a high bar to declare someone actually innocent - even someone already freed from prison. But more than 100 exonerees have been paid for their wrongful convictions.