Revealing mistake: The compound Heptan-2-one is mentioned several times in this episode. The actress concerned persists in pronouncing the last syllable 'one' as in the number 1, whereas its correct scientific pronounciation should be as in the word 'bone' ie. sounds like 'own'. Nitpicking certainly, but a dead giveaway to any viewer with a basic knowledge of chemistry.
Factual error: Using a Draeger tube to test for nitric acid fume, the instrument made a clicking sound. This device does not click. The bellows pump is squeezed drawing air through the tube. A reaction takes place between the air contaminant and the material in the tube causing a color change. The length of stain is proportional to the concentration.
Continuity mistake: The scissors are being profiled but as seen with last scissor coming in, it's discarded after only one cut of the tape. This is NOT conclusive, as the whole blade of the scissor has to be profiled, which means he has to cut the tape at least a few times, until he has covered the whole blade, section by section
Factual error: I-131 (or any radioactive material) "at the end of its half life" does not instantly become non-radioactive, as was depicted in this episode. Radioactive decay is a continuous process; the half-life has no "beginning", but tells you how much time after "now" for however much is there at any time "now" to be reduced to one half that amount. Wait enough half-lives and the amount will fall to an inconsequential amount, but one is never enough
Factual error: Firstly, I-131 has an eight day half life. It is thus impossible that she is poisoned on day 1 (a dose enough to kill her), and then the following day there is no detectable rad. reading at the source. The eight day half-life also comes into play with the hand that becomes "neutralized" to radioactivity. Secondly, the discussion re: alpha, beta, and gamma radiation is true, however if breathed/ingested, I'd sure rather it be a gamma emitter than an alpha emitter, as alphas will deposit more energy (this is contrary to what was stated).
Other mistake: In the flashbacks of the crime, the surviving toddler continually walks through the blood, making perfect little 'blood footprints' all over the house, and a trail leading into the back yard. Accompanying him walking around is a sound effect implying that the feet in the toddler's footed pj's are made of cloth...acting like a sponge...unfortunately, not only would the footprints not be perfect and long lasting, but the pj feet were plastic.
Character mistake: Horatio twice reads an extract from a letter threatening the life of the poisoned woman. The first time, he reads, "If you ever try to contact us again we will kill you," and the second time, "If you ever try to contact me again I will kill you." A close up of the letter shows it to read, "If you ever try to contact me again i'll (sic) kill you".
Factual error: During their investigation, the CSIs learn, through a number of phone calls she made to her mother, that their murder victim was in the Witness Protection Program. Contacting family members is one of the cardinal sins of WITSEC; she would have been immediately relocated with another new identity, and not left in a city where people who want her dead know where she is.