I strongly believe that Dan did miscalculate on his last jump. For some
reason he moved his jump site. In doing so he crossed the ropes (either
on the retrieval line or on the main jump line). When he jumped the first
knot above the one he was tied in with slid down a section of rope several
lengths up. The sheath was heavily melted and removed in several sections
on this upper part of the rope. The knot that slid down the rope was
melted in multiple locations and was melted nearly completely through,
deep inside the knot. This knot was not tight, yet others in the system
were (this is the one open question that is unresolved as far as I know).
It is my conclusion that Dan's rope was cut by his own rope sliding
against itself. Use of a magnifying glass indicated to me that the cut
surface was due to sliding action in one direction. There was no evidence
of hot cutting with a knife or other type of instrument. I conducted
further experiments in my lab to see if tensile overload could have caused
this failure. The samples I tested were significantly different in that
they were heavily frayed and tattered. My analysis of Dan's ropes in
general was that they were in great condition. There was no evidence to
me of damage due to previous falls, uv exposure, or weather. I would have
climbed on these ropes without any hesitation had they not been from this
accident. I do not believe that the condition of the ropes had anything
at all to do with the failure of the ropes. Nor do I believe that Dan's
basic shock absorbing setup was incorrect. Crossing the ropes was the
problem.

http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?t=41237&start=0&postdays=0&postorder=asc&highlight=