When Calliegh states that the sniper was likely Marine Corps trained and they were among the best in the world, it is not an exaggeration. USMC trained snipers routinely win or place in the top five of many of the most difficult and rigorous sniper competitions in the world.
Because of the October 2002 DC-area sniper killings, CBS considered delaying the broadcast of this episode. However, when the two suspects were arrested and charged with the sniper slayings at the end of October, the network reconsidered and chose to air the episode during the November 2002 sweeps as originally planned. The story's similarity to the DC-area sniper killings was purely coincidental and in no way inspired by the DC-area sniper slayings, since the script was written several weeks prior to the attacks taking place.
Horatio Caine when going over the evidence says, "the answer my friend is blowing in the wind". This is a quote from a Bob Dylan song.
First time that Erik's sister Marisol is mentioned, when Erik is on the phone with his sister Marisol. She would later become a serious character in the series.