Mini helicopter linked into cellular network and controlled from behind a proxy network + loaded with an explosive payload created in a clean room. Or mounted sniper rifle with a triggering mechanism linked to a communications network of some sort. The main goal is to maintain distance from the target, in order to avoid forensic trace evidence being left behind, eye witnesses and a potentially quick apprehension. Trace evidence from the firing position needs to be avoided, trace evidence on the delivery device needs to be avoided.Trace evidence on the payload is something to avoid as well, sniper rifle bullets should not be touched at any stage, of course bought with cash. Bombs are harder to remove trace evidence from. Reconnaissance on the target to plan the point of attack as well as determining the best potential escape route. Professional hitmen tend to immediately drop the weapon. All materials used should be unlinkable to the assassin. Transmitting devices should not be carried to the location the attack is launched from (the original positioning location of the UAV or remote controlled sniper rifle), identifiable vehicles should also be avoided. Depending on the specifics it may be possible to take a route that is under no surveillance to the attack launching location. Mostly the perfect murder involves avoiding leaving trace evidence on the murder weapon, payload, scene and launch location, in addition to maintaining unlinkability to any of the utilized locations or materials. Remote control mini helicopter has the benefit that it may be difficult to pinpoint the exact launch location, but the disadvantage that the helicopter and the payload it delivers (likely explosives) need to be completely free of any trace evidence. One technique that a few intelligence agencies have utilized is umbrellas with hollowed out stems that can shoot poisoned pellets out of their tips. Wear a raincoat and wait for heavy rain to coincide with the target being exposed, walk past them and launch the pellet into them from the umbrella. They feel a small sting at first and then die hours or days later, the umbrella is carried with the assassin and the poison pellet immediately dissolves in the targets body.