Some 12 minutes into the show, Dr. Price explains that the captive bolt gun works with compressed air. That's why the victim didn't have gunpowder burns around the wound. At 33 minutes, Calleigh and Delko do the GSR test to a suspect and when the test is positive, they come into conclusion that he is the murderer. However, the GSR test wouldn't be conclusive one way or another with a compressed air gun.
When Calleigh returns to the stable to check Backdraft if he'd been doped, she reaches twice to strokes his face.
The team deduces that the hit man had recently arrived from Moscow because his watch was set 11 hours ahead (and proceed to examine recent flight manifests). This is true for California, but Moscow is only 8 hours ahead of Miami.
Contrary to Dr. Price's explanation, captive bolt guns are not used to destroy the animal's brainstem, because if you do that, the animal dies instantly with its heart stopping. Instead, you use the gun on the forehead to stun, then open a major blood vessel to bleed the animal out.
Regarding the same scene when Wolfe and Horatio assumed the Russian guy had just arrived to Miami because of the time difference it is impossible to know that an analogue watch is 11 hours ahead if it is set before midnight. If that is the case the date will be the same and so the watch can be 11 hours ahead or 1 hour behind.
Trace specialist Michael Travers, speaking of horse racing, says, "Every Englishman worth his salt has done his time at the Derby." He pronounces the word "durby", like an American (or a Canadian). A native of England would pronounce it "darby".