The convict, Lester Danken admitted to defiling his two granddaughters aged 10 and 11, at Kufunda Village, Traditional Authority Kachere in Dedza, Malawi.
According to the state prosecutor, one of the victims revealed that her grandfather had been having sex with her since last year and giving her K100.
Aside from the financial reward, Danken also promised the victim that sexual abusing her would boost her breasts.
The latest act that blew his cover occurred in September 2021. One of the victims' mother reportedly saw her coming out from the grandfather's house with her underwear in her hand.
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Sub Inspector Mercy Scott who asked the court to have no mercy on the nonagenarian further disclosed that he voluntarily told Police that he defiled another grandchild.
Medical reports from a hospital confirmed that the victims were indeed defiled.
Senior Resident Magistrate Clemence Chamwenda sentenced the old man to 21 years imprisonment on each count, and the two sentences will run concurrently.
Dedza Police Deputy Public Relations Officer, Sergeant Cassim Manda confirmed the development on Friday, reports say.