Kevin Liverpool, 35, and Junior Bradshaw, 32, have denied the charges against them, which include conspiracy to murder, conspiracy to cause grievous bodily harm and conspiracy to rob the Grammy-winning pop star.
However, the jury at Exeter Crown Court was told by prosecution that the two men were armed with a sword, knives, and other potential weapons--as well as notes stating their intentions to kill the singer--when they were spotted driving around Stone's neighborhood.
The pair were cited as part of a larger group plotting to kill Stone, who was at home at the time of the alleged planned attack, according to prosecution.
"Joss Stone is an extremely wealthy young woman," noted prosecutor Simon Morgan. "These defendants drove from Manchester to find her."
Liverpool and Bradshaw were apprehended by police in June 2011 in the Devon town of Cullompton after "eagle-eyed" residents of the community did not recognize their car. They were a few miles away from Stone's house.
The trial is anticipated to last about three weeks, and Stone is not expected to attend.
The 25-year-old singer has sold 13 million albums over the course of her career, and currently holds the title of fifth richest British musician under the age of 30.