49ers defensive back Perrish Cox sat out last season while dealing with a sexual assault charge for which he was subsequently acquitted. The woman is now suing Cox and Denver Broncos wide receiver Demaryius Thomas in a lawsuit claiming battery, sexual assault and battery, conspiracy, outrageous conduct and negligence (copy of the complaint). Thomas was not charged in the original criminal investigation.
Cox was acquitted in March, but could still lose the civil suit based on the burden of proof. In a criminal case, the prosecution must prove guilt beyond a reasonable doubt. That basically means the jury needs to be certain of the defendant's guilt. There can be crazy theories, but reasonable doubt basically means removing reasonable alternatives.
In the civil case, the burden of proof is preponderance of the evidence. That basically means the jury will need to believe one side more than the other, even if it is merely .01% more. If they believe the plaintiff more than Cox and/or Thomas by any margin, they would need to decide for the plaintiff.
The most significant difference is in some of the evidence involved. Apparently there was a belief that the plaintiff might have been drugged at some point earlier in the evening. It appears the prosecution elected not to pursue this avenue of the case. In a criminal case, the prosecutor has the ability to make all necessary strategic decisions. In a civil case, the plaintiff's attorney is working directly for the plaintiff, so additional issues could be brought up in the case.
Although Cox was acquitted of the charges in March, he still could face a suspension by the NFL. The league has not announced a decision with regards to potential discipline. Even though Cox was acquitted, the NFL has shown that its discipline process operates independent of any court decisions. The most prominent example was Ben Roethlisberger's suspension without having been charged with a crime (think what you want of it).
From a purely football perspective, Perrish Cox is in a very interesting position heading into training camp. He brings special teams potential while also getting a shot at cornerback playing time. Although the 49ers would appear to have their top three cornerbacks locked in (Rogers, Brown, Culliver), they remain fairly limited at the safety position. It is possible they might find themselves leaning a bit more on cornerbacks when they go to more DB-heavy defensive formations.