Duties of Nonparties Who Hold Critical Evidence
Law.com has an insightful article posted up on the duties of nonparties who hold critical evidence. Parties to a lawsuit, and those who reasonably should anticipate they are likely to become parties to a lawsuit, have a duty to preserve evidence. In some circumstances, that duty includes preventing the routine destruction of evidence, such as by a surveillance system that "tapes over" itself every few days, or an email system that purges old emails every few months. If a company should have actual or anticipated litigation on its mind, the company can be sanctioned for the spoliation of evidence through its routine destruction.
But what about a nonparty? If two of your customers are in the middle of a hostile lawsuit, and you have a mass of relevant emails from both customers, do you face exposure to legal penalties if you don't lock those emails down? According to Law.com, no:
In short, those outside the caption are spared the preservation burdens the combatants bear.
However, that protection likely ends once the nonparty is served with a subpoena for the evidence. At that point, destroying evidence responsive to a subpoena can be punishable by contempt of court.