Twelve sailors and one captain are aboard a sail boat.
One passenger is murdered and no one is confessing to the crime.

One sailor decides to let the cards discover the guilty person.
The person who gets the four same cards will be the murderer.

Here is how the sailor procedes :

Get a deck of cards.
Remove the jokers.
Arrange each suit in order from the ace to the king.
Make one stack.
Cut the deck of cards 13 times (one time for each sailor and once for the captain.)
Distribute the cards in this way :

1    2    3   4    5    6
             7
13   12   11  10   9   8  

Then reverse the distribution of cards starting at 13 and stopping at 1.
Start the distribution again  (1 to 13  then 13 to 1)
Distribute all the cards.

The captain is number 7 and stands between the sailors.
Point to any sailor and ask that the cards be shown.
The captain will be the last person asked to show his cards.

Who is guilty?

Watch the video