See, she installed a nanny-cam in a picture frame so she can amass evidence for the inevitable divorce proceedings. Fin grabs the USB flash drive from the fanny-cam, I mean nanny-cam.
At the station, the detectives watch with Kona a little scene with a post-coital Julie in bed, trying to take a picture of Kona with her cellphone. He says "no pictures" and then goes apeshit when she ignores him, and the clip is paused with Kona about to smack her. The detectives barrage him to try to get him to confess to the murder, but he maintains that all he did was give Tracey a little slap, and points out the detectives saw the video, in which the "little nympho" was all over him. And the questioning is broken up by a lawyer for Not UFC, who says he's got records of Kona's membership card being swiped at the gym at the time of the murder. When the detectives point out it's easy to get someone else to swipe a card for him, the lawyer provides club surveillance camera recordings of Kona's coming and going. Well, open with that, then. It drives me crazy the way defense attorneys on this show always lead with the easily fakeable evidence when providing an alibi instead of just opening with the incontrovertible proof. Chester wants to charge Kona with battery at least, but Cragen kiboshes that after the defense attorney points out that the only way to get that charge to stick would be to play the sex tape in court, in front of the father of the dead-either-way victim.
On the way out, Mr. Badass Defense Attorney says he'll have their badges for putting Kona through this, instead of just shutting up. Sets a good example for his client, for sure, since when Chester says Kona's lucky they didn't charge him with the battery, Kona says, "I see you on the street, pretty boy, you're dead." I'm no lawyer, but I think I could handle telling my client that it's not advisable to threaten a cop. Especially in a police station, with many other cop witnesses around. The lawyer just says, "Don't waste your time," and they leave.