allows for more accurate shots, because the cross-hairs can be aligned with the target more accurately, but the sniper must know exactly what differences the changes will have on the point-of-impact at each target range. For moving targets, the point-of-aim is ahead of the target in the direction of movement. Known as "leading" the target, the amount of "lead" depends on the speed and angle of the target's movement as well as the distance to the target. For this technique, holding over is the preferred method. Anticipating the behavior of the target is necessary to accurately place the shot. Hide sites and hiding techniques The term "hide site" refers to a covered and concealed position from which a sniper and his team can conduct surveillance or fire at targets. A good hide conceals and camouflages the sniper effectively, provides cover from enemy fire and allows a wide view of the surrounding area. The main purpose of ghillie suits and hide sites is to break up the outline of a person with a rifle. Many snipers use ghillie suits to hide and stay hidden. Ghillie suits vary according to the terrain into which the sniper wishes to blend. For example, in dry grassland the sniper will typically wear a ghillie suit covered in dead grass. Shot placement Shot placement, which is where on the body the sniper is aiming, varies with the type of sniper. Military snipers, who generally do not shoot at targets at less than , usually attempt body shots, aiming at the chest. These shots depend on tissue damage, organ trauma, and blood loss to kill the target. Body shots are used because the chest is a larger target. Police snipers, who generally shoot at much shorter distances, may attempt a more precise shot at particular parts of body or particular devices: in one incident in 2007 in Marseille, a GIPN sniper took a shot from at the pistol of a police officer threatening to commit suicide, destroying the weapon and preventing the police officer from killing himself. In a high-risk or hostage-taking situation where a suspect is imminently threatening to kill a hostage, police snipers may take head shots to ensure an instant kill. The snipers aim for the medulla oblongata to sever the spine from the brain. While this is believed to prevent the target from reflexively firing their weapon, there is evidence that any brain-hit