When Catherine is running through the house at the beginning of the episode, she runs past a mirror (or a door w/ a reflective surface). The camera and crew are clearly visible (evenif only for a split second via frame-step) in the reflection.
When figuring out what the criminal's "fruity scent" is caused from, Grissom tells Katherine that it's because of Diabetic Ketoacetosis, which is treated with Novolin Insulin. This, however, cannot be the case since Ketoacetosis is, in fact, a very debilitating complication that can result from diabetes, which would either require extensive hospitalization or, in less severe cases, a treatment that would last, at most, a single day. Not only that, but Novolin Insulin isn't a specific type of insulin, it's a genetically similar to human insulin created by Squibb-Novo, making it a brand name instead of a treatment, and would, more than likely, be a constant running medication instead of just for the one condition.
When Horatio is in the lab to make the comparison of the honey sample he collected at the club with the honey found on the body, a microscope is used and the samples are declared "identical." There is no way a visual comparison could reveal this - instead it would require chemical analysis.
Catherine smells bottles in the limo and declares the first bottle is vodka and the second is gin. It is in fact just water in both prop bottles - vodka is much clearer and gin has a very slight green hue.