Neil Cooper (played by Tom Mannion) is a con artist who appears in "The Con is On". In the episode he helps out Mickey and the team by impersonating Martin Depalma, a police officer.
Posing as Martin, Neil joins the police team that is investigating Mickey and the gang. We see him through out the episode working with the police but its not until the end, when it's been revealed to Danny, that we find out.
Posing as a police officer he pretended to shoot Mickey dead when he was pointing a gun at Danny, signed the team out of jail and signed out all the evidence in the case.