There is no doubt that the Participant is entitled to name a beneficiary or beneficiaries to all of his assets including those within a defined contribution plan (that I assume this is but you didn't say). The Participant's account does not revert to the Plan so it has to go somewhere.
This places to name a beneficiary includes the execution of a Last Will and Testament with respect to houses, cars, furniture, investments, boats, yachts and airplanes and most other stuff with respect to which do not pass by operation of law, like life insurance or T/E real property or a beneficiary designation.
If the deceased dies intestate (without a Will) and fails to name a beneficiary, or if the beneficiary previously designated predeceases the Participant, or if the deceased failed to name a beneficiary with respect to ALL of his 401(k) plan account, there are two places to look. (i) The Plan document may itself provide that in the absence of a beneficiary designation the asset with pass to specified categories of people. For example, under Federal TSP the order of preference is:
1. To your widow or widower.
2. If none, to your child or children equally, and descendants of deceased children by representation.
3. If none, to your parents equally or to the surviving parent.
4. If none, to the appointed executor or administrator of your estate.
5 If none, to your next of kin who is entitled to your estate under the laws of the state in which you resided at the time of your death.
(ii) If the Plan does not have such a provision the assets wind up in probate court and pass according to the decedent's Will if he dies testate, or, if he died intestate then in the order of preference set forth in state law.
I don't think you can suggest that the now mortis est Participant really meant to leave 100% to the beneficiary in this case. It would be more logical to conclude that Participant intended to leave the 2nd 50% to the fist person on this blog to use the Latin phrase mortis est.*
David
*Dead is.