Kill a Man - Marry the Widow?

Kill a Man - Marry His Widow?

In childhood, I remember having one of those books of random facts and trivia (I believe it was Felton & Fowler's Best, Worst, and Most Unusual) - which claimed to be telling me the ways of an African tribe, in which the penalty for murder was replacing the dead man; you had to do his job, assume his obligations, and marry his widow if he left one.

I've never seen it confirmed, but I've seen it used twice in comedies. One is in an early Abbot and Costello movie - The Winsome Widow of Wagon Gap (Costello's character travels to a western town that has this custom -he accidentally kills a bad man with a mean, mannish, and homely widow, whom he has to marry - on the strength of this deed, he becomes the sheriff, for one one dares to touch him - and he carries her picture instead of a pistol...). The other is in Gilbert and Sullivan - in one of the last two plays they did. (They'd always quarreled, and they broke up after The Gondoliers over an argument about carpets - but they got back together twice, and wrote two of their best but least-known plays.) This was The Grand Duke - subtitled The Statutory Duel - and here is a link to the song that explains it all. However, this recording is lacking the first couple of lines:

About a century since
The code of the duello
To sudden death, for want of breath,
Sent many a strapping fellow.

The then-presiding prince,
Who useless bloodshed hated,
He passed an act, short and compact,
Which may be briefly stated...

...listen to it all; but the upshot is that the prince replaced duelling with the simple draw of a card, and whoever draws the low card is legally dead, and the other man must "discharge his debts, pay all his bets, and take his obligations." (How this would square with Grim's view of duelling among our ancestors as expressed a few posts ago - the point being a man's ability to die for his position, whatever the facts of it - this I won't think about for now.)

Time for searching around is very short for me - my new assignment carries a heavy guilt load. Does anyone here know whether such a custom ever existed?