Keith Mukata, a member of the opposition United Party for National Development, was found guilty of first degree murder by the Lusaka High Court.
Presiding judge Susan Wanjelani sentenced Mukata to death by hanging, but acquitted his girlfriend and co-accused Charmaine Musonda.
The two were both accused of killing security guard Namakau Kalila Kwenda at a law firm in the capital.
Justice Wanjelani said the fact three cartridges were found inside the gate confirms the deceased was shot by a person face to face.
Mukata’s lawyers have indicated they will appeal the sentence.
As much as Zambian laws provide for death penalties, convicts usually have their sentences commuted to life in prison instead.