Crucial evidence was left when Ms Boulton, of Ash, scratched McKenzie’s face.
DNA was discovered under her fingernails which proved critical in securing McKenzie’s conviction, police said.
Detectives said McKenzie went on to construct an “elaborate cover-up” involving claims of being a victim of a robbery in an effort to explain why the DNA was found under Ms Boulton’s fingernails.
Det Ch Insp Kimball Edey said: “McKenzie’s motive for killing Joy was simple – she wanted what Joy had.
“McKenzie has a previous history of jealous behaviour.
“McKenzie went to Joy’s that morning with the sole intention of killing her so that she could get Trevor back. The rage and brutality McKenzie used when she attacked Joy cannot be overstated – sadly, Joy never stood a chance.”
Paying tribute to Ms Boulton, her family said: “We are deeply devastated by this senseless act of violence which has changed our lives forever.
“Joy was a very caring person, who was always ready to help other people whenever she could, despite having many health and mobility problems herself.”
