Twists & Turns of Phrase
By extension we also get the adjective dead-handed, which means oppressive and out-dated. For example, a teenager might rail against his parents’ dead-handed authority.
The phrase dead hand, which inevitably puts me in mind of zombies and rigor mortis, actually has medieval origins in French property law. Although church leaders were the ones in practical possession of lands and monies, they didn’t want this wealth reverting automatically to the state upon their death. So instead the institution of the church was defined as an individual under the law. Since it could never die, nothing need be forfeited to the state. Thus such property was said to be in the dead hand (or mortmain) of the church.
The concept of mortmain was taken up in medieval England and was used there in the same way. Since then, the dead hand has also applied to the holdings of charities and other corporations.
From this legal meaning, the phrase dead hand slowly came to mean anything that is an “oppressive or retarding influence.” (OED)
Someone who is an expert at something can also be described as a dead hand: She was a dead hand at throwing darts.