After killing off all of Sadono's guards, lure him into a dark corner then shoot him with a Ring Airfoil. Then, run up behind him and grab him. You can now force him to use the retinal scanner and complete the mission. Also, rather than picking off each one of the bodyguards, you can go to the right all the way around the room in the shadows. You should then reach the stage behind Sadono. Follow the curtain's shadow to Sadono. There will be a gap. Stand up and run until you see the "Grab Character" option appear. Grab him. You will be shot at and probably get hit, but once you grab him they will stop and you will hear someone say "Don't shoot, you might hurt Sadono". After that you are home free as they will not follow you.