There is some discussion ongoing concerning about the visible damage of the cockpit section and how that could be conclusive concerning the inbound path of the SAM and distance of explosion of the warhead or the type of warhead.
The following link has very good information about the BUK1 system and also pictures about the structure of the missile.
9K37/9K37M1/9K317 Buk M1/M2 / SA-11/17 Gadfly/Grizzly / C????????? ???????? ???????? ???????? 9?37/9?317 ??? ?/?1/?2
Few points I like to point out:
The diameter of the mxl without the winglets is about 40cm, with wings about 86 cm(later types 120cm), the length is 5,55 meters. Most uninformed people think the warhead being at the pointy end of the mxl, which is not the case. There the seeker head with the semiactive radar and all the electronics are located in a space of about 1 meter from the tip of the mxl to the warhead behind.The warhead is designed to explode to the forward and outside, thus not only fragmenting the warhead casing to the designed fragmentation pattern, but also the 1 meter long guidance unit in a random way. Therefore the damage pattern might not be consistent with what's expected from the warhead fragments alone.
The part after the warhead will be less effected from the warhead detonation and could therefore be found in identifiable proportions, especially the wings and the hull of the solid rocket propellant. The location to look for such items would be close to the cockpit section, where the explosion most probably was nearby. If somebody would like to trick with evidence, then the first task would be to search for such missile parts and get them out of the way.
There was one picture published where a greenish O-ring gasket like those seen in joints of missile sections could be seen. But it was hard to judge the diameter and i have no knowledge if such sized gaskets are used in the 777.