The computer is capable of detecting life signs and detecting the locations of people on the ship, this much has been established. It would make sense that it would log these events, for at least a short period of time. It's not a stretch to think someone with proper security clearance could just ask the computer: "Who was the last person to enter Keyhlar's quarters before Worf entered at 0500(or whatever)?"
In addition I'm sure they could find Duras's DNA somewhere in the room/on Keylar after the struggle.
Those pieces of evidence, along with worf's testimony that keylar TOLD worf that duras was her killer, would be enough I'd think. The computer may even have the ability to playback what she said to worf as she died, in case there is any doubt that he would be making it up.
Of course, these things can be tampered with, but that could be looked into as well.