First you have to understand what a "Dead Man's Hand" is.
The makeup of poker's dead man's hand has varied through the years. Currently, the dead man's hand is described as a two-pair poker hand consisting of the black aces and black eights. Along with an unknown "hole" card, these were the cards reportedly held by "Old West" folk hero, lawman and gunfighter, Wild Bill Hickok when he was murdered.
And the Fifth Card?
there are various claims regarding the identity of Hickok's fifth card, suggestions that he had discarded one card or that the draw was interrupted by the shooting and Hickok therefore never received his fifth card.
Historical displays in the town of Deadwood, including one in a reconstruction of the original saloon, display the nine of diamonds as the fifth card. The Lucky Nugget Gambling Hall, at the historic site of Nuttal & Mann's Saloon, displays a jack of diamonds instead. The old Stardust Casino on the Las Vegas Strip had used a five of diamonds in related displays. The western-themed collectible card game Doomtown (and its rebooted expandable card game, Doomtown: Reloaded) uses the Dead Man's Hand as the highest rank in the game, and uses the Jack of Diamonds as the fifth card.
Alternatively, you may be asking the simple question....!!!
The fifth of 5 cards dealt face up to the community card board is known as the "River". The river or river card is the final card dealt in a poker hand, to be followed by a final round of betting and, if necessary, a showdown. In Texas hold 'em and Omaha hold'em, the river is the fifth and last card to be dealt to the community card board, after the flop and turn. A player losing the pot due only to the river card is said to have been rivered.
