The LCPD Police Snipers is an LCPD marksmen team in GTA IV, deployed at a five star wanted level on. They are found on the roofs of buildings such as Vespucci University in Varsity Heights and The Triangle building in The Triangle.
They are regular police officers seen patrolling the streets of Liberty City. The only difference is they carry Combat Snipers and are much more acurate with their weapons. When disarmed they use pistols which they are also accurate with. The problem with them being so accurate is it makes it just a little bit harder to not get killed. Sniper rifles are extremely powerful and getting shot with one even with a vest on takes away lots of protection. Getting shot without protection allows the player to be killed in two shots as with protection takes four to five shots as noted when getting shot with a sniper rifle. The closer the range the less bullets it takes to bring the player down. Close range can kill the player in two shots with protection and one without.
If the player is in a vehicle pursuit the best thing to do is have the back facing the snipers. If they are on foot it is better to stay running along the walls of the buildings they are on the roofs of. It is also good to use alleyways and vehicles for cover when moving around on high wanted levels so not to get caught by a sniper bullet.
It is possible the officers have N.O.O.S.E training even though they work for the LCPD. Or there may be a special range for their unit to train on marksmenship as other officers get basic training.