was it designed properly?
lawyers & insurance companies will hire other engineers to review the design. if the design was flawed, then it's an epic engineering failure. if the design was sound, next question:
was it constructed in accordance with the design? if the answer to the first question is "yes", then the answer to this question is undeniably "no"....
then the next question is: why?
I've designed a few mechanical (not structural) systems that were not constructed as designed. My firm actually had a contractor argue that because we didn't catch his (unauthorized) changes and/or mistakes, that it was our fault.