Neutral Referee in IP dispute between former joint development partners

In the spring of 2017, I was approached by lawyers from two technology companies working in civil avionics (instruments for airplanes).  I can't say who they were due to NDA restrictions, but the job was an unusual and interesting one.  The two companies had been joint development partners, but the relationship had soured and trust had now broken down completely.  Both were concerned that the other was misusing intellectual property disclosed during the joint venture, and they asked me to do do an audit to see whether this was in fact true.  The situation was made more complicated because one company was several hundred times as large as the other, and of course there was no court-ordered discovery and no one was under oath.

After interviewing engineers for both sides and visiting SmallCo's facility, I was able to report that SmallCo's development pattern was essentially unaltered following their interaction with BigCo, and that in fact there was no evidence that BigCo had actually transferred the IP they claimed to be most concerned about.  (BigCo, like many large corporations, has a policy of deleting email archives more than a year or so old.)