The expression "hoist by their own petard" originated in the late middle ages. A petard was an explosive charge w/ which besiegers would attempt to demolish a castle wall. But explosives being in their infancy, sometimes the device would explode while being placed -- and the besieges would be "hoist by their own petard."

The colloquial use of the expression is epitomized by the sad fate of Clement Vallandigham. Clement was the leader of the Civil War "Copperheads" -- Northerners who vehemntly opposed the War arguing that the South could not legally be compelled back into the Union and bitterly assailing Lincoln for his many unconstitutional acts.   Tried for sedition, Vallandigham was convicted and banished to the Confederacy from which he eventually departed to live in, and oppose the war from, Ontario.

After the War Vallandigham returned to the U.S. and resumed his practice as a lawyer. In 1871 he was defending a man accused of murder. Vallandigham defended on the theory that the deceased had been pulling his own pistol which had caught in his clothing and discharged, killing him. Vallandigham was demonstrating this by pulling his own pistol which caught in his clothing and discharged, killing him.
His client was acquitted.