The Magician, Tobias Strange says C-4 is too volatile and unpredictable to use in a magic act, but C-4 is actually a very stable explosive which is very insensitive and has to be detonated by a shock wave from an explosive detonator. Additionally, it has a clay like texture and can be molded into any shape..
After Detective Esposito hands Beckett the criminal records of a suspect you can see the document for a brief second. On the document is listed the suspects SSN however they forgot two of the numbers.
In "Poof You're Dead," C4 is described as "volatile and unpredictable. It is neither, which is why it is used so extensively in military, industrial, and demolition applications. Because of its explosive power, it can be extremely dangerous if misused, which is why only licensed and certified experts may use it legally.
Lainie holds up an evidence bag with large tangled tufts of white fur inside. Later it is revealed that it was supposed to be fur from the perpetrator s gloves that was stuck to his hands and transferred to the face of the person he smothered with his bare hands. The amount of fur in the evidence bag was way to much to have been on a person's hands and transferred to a victim. It was also too long to have come from a glove's lining.
Beckett states the magician's warehouse is located in the Bronx, at the end of the subway line. Notwithstanding she did not state which subway line, when she and Castle arrive at the warehouse, it is on the East River, and the Brooklyn Bridge and the Manhattan skyline are in the background. You cannot see the Brooklyn Bridge from anywhere in the Bronx, especially the last subway stop.
Lainie says the evidence indicates the victim drowned, then a few moments later she says he was dead before he hit the water. He could not be dead before he hit the water AND drown, it has to be one or the other.
Becket pronounces Poughkeepsie incorrectly as 'P·oo·kip·sie', emphasizing the first syllable. The usual pronunciation places the emphasis on the second syllable, 'P·uh·kip·sie'.