Afriyie also stabbed his rival, Kwaku Ofori, a tipper truck driver, on his back, the left arm and in the chest in an attempt to kill him.
But Ofori survived.
Although Afriyie pleaded not guilty to attempted murder and murder, the seven-member jury pronounced him guilty after a full trial.
The presiding judge, Mr Justice Edward K.B. Apenkwah, sentenced him to 10 years on the first count and to death by hanging on the second count of murder.
The court had heard that the convict and the deceased lived together in the same house belonging to her elder brother.
According to the prosecution, although the two were said to be related, they were in a secret amorous relationship.
When news of their relationship got to the attention of Frimpongmaa’s elder brother, he cautioned them to stop it as it would amount to incest.
Although the two initially denied the relationship, Frimpongmaa later confessed to her brother, broke up with Afriyie and got into a new relationship with Kwaku Ofori, a resident of Sefwi Wiawso.
Around 10:30 p.m. on January 7, 2013, Ofori, who had gone to visit Frimpongmaa at Atwima Techiman, went to take his bath and entered Frimpongmaa’s room where he was to spend the night.
Afriyie, who had then returned from work and was drunk, barged into the room armed with a knife and tried to stab Ofori.
Ofori used his left arm to parry the knife and Afriyie struck a second time, hitting Ofori’s chest. As Ofori was escaping from the attack, Afriyie further stabbed him at the back.
According to the prosecution, Ofori managed to escape from the scene and Afriyie turned his rage on Frimpongmaa, stabbing her several times on the neck.
After the act, the convict went into his room, which was close to the deceased’s, and locked himself in.
He was later apprehended and handed over to the police.