A deep finesse occurs when three or more cards are missing
higher in rank than the card finessed. This deep finesse is often made in order to
execute a suck or avoidance play, but can be a genuine play necessary
to achieve the best result.
Deep finesses have proven to have a greater mathematical
percentage of success, than when the finesse is not taken.
Several examples follow
which illustrate the Deep Finesse.
Example 1
A Deep Finesse is when South plays the 2, and finesses West with the 10. This finesse has proven to contain the highest percentage play. If West, however, plays to the trick with a low card, the percentage rate is higher of South taking the trick is if South plays the Queen.
Example 2
South leads the 3, West plays low, and the highest percentage play is for South to play the 9.
Example 3
South leads the 2, West plays low, and the highest percentage play is for South to again play the 9.
Additional Examples
Although the following examples may not fit into the playing habits of most bridge players, a deep finesse is still mathematically the correct procedure to ensure the highest percentage play, when leading from a singleton.
Example 1
Example 2
Example 3
In all of the above three examples, the percentage rate of success is highest if South, upon leading the singleton, deep-finesses with the 8 on the first round.
History of Deep Finesse
The origins of the concept of a deep finesse begin in the days, when the game of Whist was all the rage and the modern card game. In the publication by Mr. George William Pettes, aka G.W.P., titled American Whist Illustrated: Containing The Laws and Principles of the Game, The Analysis of the New Play and American Leads, and a Series of Hands in Diagram, first published by Houghton, Mifflin, and Company / The Riverside Press, Cambridge, in the year 1890, the deep finesse is considerably analyzed, not only from the standpoint of the mathematical percentages, but also from the purely logical side.
Mr. George William Pettes mentions the deep finesse several times in his publication and the following is but a short excerpt from his book, which was first published in the year 1890.
Perhaps there will be some difference of opinion between players about deep finesse and the forcing of partner when weak in trumps. But there need be no question in the mind of any strong player holding the tenace and other trumps as to the propriety of deep finesse in a plain suit, that if unsuccessful throws the lead; or of giving partner an opportunity to make a card of his best perhaps his only suit before he hurries him to trump a low card, necessitating a return lead that cannot probably be made to the best advantage.
If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.