|Minor Character: New York|
|Occupation||Irish Mob Leader|
|Portrayed By||Shane Brolly|
|First Appearance||Snow Day|
Colm background is unknown as not much is revealed about him. He has a relative who served with the IRA and at some unknown point began working for Gavin Wilder under his crime family.
He later learns that someone in the FBI was investigating the whereabouts of his unknown relative and took matters into his own hands. He cornered the FBI special agent Candace Broadbent and shot her in the head, execution style.
He later decides to take leadership of Wilder's crew and subsequently shoots him in the back with a high-powered rifle. His reign over the gang, however, is short lived as Flack and his team successfully seize 900 kilograms of cocaine and heavy weaponry from his crew and arrests many in his outfit. But Colm is not dissuaded and devises a plan to get the cocaine back. After the drugs are taken back to the lab, while Adam is left behind to process the scene, two of Colm's men take him and the two cops guarding the scene, hostage. They then torture Adam for access codes and information on where their drugs are. Later Danny arrives after being sent to help him, but when Danny arrives he's hit over the head and taken prisoner.
Then Colm leads a group of his men into the crime lab by faking a gas leak, causing the lab to be evacuated. Mac and Stella however do not take the bait and stay behind. Colm then leads his men to the Armory where they take the high powered rifle to cut the door, leading to their drugs, open. Colm notices that people are still in the lab and takes two of his men in search of them. They spot them and open fire, and in the process he accidentally kills one of his own men.
Back at the warehouse the thugs force Danny to call Flack, and the homicide detective brings a team to the warehouse where he's met by Lindsay, who came to work and learned Danny had been abducted. The abductors prepare to disguise themselves as cops and send the real cops out dressed in their clothes, but Danny foils their plans by throwing the Marquis Solution in their face. Lindsay takes charge of the badly wounded Danny while Flack and his team discover gas canisters in one of the abductor's cars and realize the gas leak at the lab was faked.
Back at the lab, Mac, Stella and Hawkes have taken steps to prevent the gang from making off with the drugs. Back at the crime lab the CSIs figure out that Colm killed both Gavin and Candace and Mac confronts Colm with this information. Colm tries to escape but he and Mac get into a fistfight and Colm lunges for his gun—falling into a booby trap Mac set earlier and blowing himself—and part of the lab—up in the process.
- Presumedly committed numerous unknown crimes prior to Sweet 16
- November 26, 2006: Agent Candace Broadbent (shot execution style)
- May 16, 2007:
Victims by Proxy
- May 16, 2007: The following were taken hostage at the warehouse crime scene (no fatalities)
- Jackie Doyle
- Sean Kelly
- Billy Morrison
- Bobby Maloney
- Unknown Irish man