Well, Vicki is so desperate to find something out about her past, she'll cling to any possible scenerio, no matter how desperate it is or unlikely it seems.
I find it hard to believe that Burke would be so shocked about Bill's death myself. Especially since he was all but accusing Roger of having something to do with Malloy's disappearance a few episodes ago.
I got the feeling Burke was just dying to name Sam as a possible suspect to what happened to Bill in front of Maggie, but restrained himself. [spoiler] So he has the decency to wait until she throws a dinner party between her, her father and Vicki to barge in, invite himself in, to make all kinds of accusations. [/spoiler] Don't know whether to admire his nerve or slap him one.