The court heard that Mr Murray, from Chingford, east London, promised his dying colleague he would find those responsible for the shots that were fired from an embassy window.
Giving his judgment on Tuesday morning, Mr Justice Martin Spencer said that “those responsible for the shooting of Yvonne Fletcher also bear liability” to Mr Murray.
He added: “I am satisfied on the balance of probabilities that there existed a common design to respond to the planned anti-Gaddafi protest by using violence.”
The judge said the evidence pointed to Mr Mabrouk being an “active participant” in a “common deign to fire upon the demonstrators”.
He concluded: “Mr Murray has succeeded in showing that the defendant Saleh Ibrahim Mabrouk is jointly liable with those who carried out the shooting of Yvonne Fletcher, for the battery inflicted upon her”.
The judge’s ruling was met with applause in a packed courtroom, with Mr Murray shedding tears as the judgment was read out.
In a statement following the ruling, Mr Murray said “we have finally achieved justice for Yvonne”.