I could only find a single botched execution reference myself, from a single eyewitness account. I saw it first in the Wikipedia article, here: https://en.wikipedia.org/wiki/Execut...#Louis_Mercier . The text is:
From there you can do the trick where you enclose a phrase or a part of a phrase in double-quotes when searching, to find the exact phrase, so the search query would look like this, of course including the double-quotes:is this really the same man that I see being jostled by four assistant executioners, forcibly undressed, his voice drowned out by the drums, trussed to a plank, still struggling, and receiving the heavy blade so badly that the cut does not go through his neck, but through the back of his head and his jaw, horribly?
"receiving the heavy blade so badly that the cut does not go through his neck, but through the back of his head and his jaw"
Those results mostly look like rehashes of the Wikipedia page, so I don't know if we'll find anything beyond that single quote.
This gruesome task reminds me of one of my favorite jokes, that plays on how obsessive tech-minded people can be about problem-solving. You can substitute "engineer" in the joke below with "computer programmer" or various other tech-oriented professions. Goes like this:
A priest, a lawyer, and an engineer were set to be executed by hanging.
The priest went first. He walks up the steps on the gallows, puts his head in the noose, the executioner pulls the lever, and nothing happens. He seizes on the opportunity and says: "This was an act of God - divine intervention. You must let me go." So they let him go free.
Next up is the lawyer. He walks up the steps on the gallows, puts his head in the noose, the executioner pulls the lever, and again nothing happens. He says: "You can't try to hang me again, that would be double jeopardy. You must let me go." So they let him go free.
Last up is the engineer, who has been watching this all very closely. He walks up the steps on the gallows - then all of a sudden, he stops.
He bends over, looks carefully at the lever mechanism under the gallows, and says:
"Well, here's the problem!"