From a very interesting article over at The Daily Caller from death penalty skeptic Marc Hyden:
The 18th century Italian philosopher Cesare Beccaria heavily influenced the views of many of America’s founders, according to John Bessler, author of The Birth of American Law. Beccaria’s philosophy helped mold our nation’s criminal justice system as it shifted away from Britain’s “bloody code.”
Beccaria, like many early American leaders, opposed capital punishment because he believed that the death penalty was neither useful nor necessary. He concluded that it served no deterrent and wasn’t imperative considering that alternative punishments could be implemented to replace the death penalty.
Any punishment that isn’t absolutely necessary is a form of tyranny, according to Beccaria. George Washington was likely well-versed in Beccaria’s philosophies as well.[According to Bessler,"In 1769, George Washington bought a copy of Beccaria's book, "On Crimes and Punishments," first published in Italian 250 years ago and translated into English in 1767"---TVD.]
And, as a general, Washington even pleaded with congress to limit capital crimes on multiple occasions.
Even though Washington begrudgingly signed death warrants in his day, he said, “We should not introduce Capital executions too frequently.” He was known for pardoning the guilty and granting clemency as a general and even into his presidency.
Some probative quotes, drawn also from John Bessler's oft-quoted National Law Journal essay:
“I should not regret a fair and full trial of the entire abolition of capital punishments by any State willing to make it.”—James Madison
"The name of Beccaria has become familiar in Pennsylvania, his authority has become great, and his principles have spread among all classes of persons and impressed themselves deeply in the hearts of our citizens."—William Bradford, Madison friend and attorney general of Philladelphia, author of An Inquiry How Far the Punishment of Death is Necessary in Pennsylvania 
“It is better 100 guilty Persons should escape than that one innocent person should suffer.”—Benjamin Franklin
“The Supreme Being alone possesses a power to take away human life, and that we rebel against his laws whenever we undertake to execute death in any way whatever upon any of his creatures.”—Dr. Benjamin Rush
"Beccaria and other writers on crimes and punishments had satisfied the reasonable world of the unrightfulness and inefficacy of the punishment of crimes by death."—Thomas Jefferson
“I shall ask for the abolition of the Penalty of Death until I have the infallibility of human judgment demonstrated to me.”—Lafayette
Unfortunately, even as one of the original authors of the French Revolution, the Marquis de Lafayette's sentiments didn't hold when it came to another "bloody code," what they came to call The National Razor--the guillotine--but that's another story. In between lies our American Founding and our Eighth Amendment, which enjoyed neither the cruelty of cousin England nor the ritualized murder of the First Republic.
See also American Creation founder Brad Hart on this subject here.