Based on my experiences (most often as counsel to the decision-maker) with several situations in which a designated beneficiary killed the participant, I’ll tell you that a plan’s fiduciaries often don’t recognize fully how their decisions and communications can get scrutiny from many directions, including not only the named primary beneficiary, a named contingent beneficiary, a default beneficiary, and the personal representative of the participant’s estate, but also the alleged killing’s prosecution and defense lawyers (because either “side” might perceive strategic advantages or disadvantages that turn on whether a defendant has or lacks a right to get money).
Even if the plan’s sponsor/administrator has excellent written claims procedures and long experience with flawless claims-handling, a slayer situation might put them to the test.
Also, the plan’s administrator should not assume (at least not without its lawyer’s advice) that even a proven slaying would undo the slayer’s benefit. Unless the plan’s governing document states a provision, there might be no clear rule.