The allegation was made during the Lakers' first-round Western Conference playoff series with Phoenix and had been under investigation since. Brown had denied any wrongdoing and was never arrested.
Deputy District Attorney Darci Johnson wrote in an evaluation of the case that the decision not to prosecute was made after "a medical exam of the victim was reviewed and revealed no signs of forcible sexual assault." There was also no corroborating forensic evidence found and Brown's attorney refused to allow him to talk to police.
The woman claimed the assault occurred in the early-morning hours of April 29, hours after Game 3 of the playoff series, which Phoenix went on to win.
In reasoning against filing charges, the evaluation described the claim as a "one on one" allegation.
The woman "admits engaging in some consensual activity" with Brown prior to the alleged assault and she remained in his home for several hours afterward, it said.
The woman's statements were consistent, the evaluation noted, but "the lack of physical evidence or a statement by the suspect means the case cannot be proven at the appropriate standard."
In his statement, Brown denounced what he called "completely unfounded allegations."
"And even when the truth is finally determined the stain of an allegation remains with no real recourse against or penalty to the accuser," the statement said.
"There is no point served by any further comment on the situation and I simply would like Laker fans to know that I am putting it behind me and focused on advancing my career and helping my team in any way I can," it added.