(at around 31 mins) The camera in the lab is facing away from Jesse, when the next shot shows the camera's view, it is aimed directly at Jesse.
Right after Hank says "Clean as a whistle" and the shot changes, there's briefly a boom mic visible in the top center of the shot.
When Jesse confronted Walt he said that only Walt and himself knew of the poison in the cigarette. How then was Walt able to convince Jesse that Gus would have arranged to have the cigarette removed, not knowing what was in it, and then use the contents to poison the child ?