The prosecutor told the court that the killers planned to sell the victim’s organs for use in witchcraft.
He said the fifth defendant was released because there was insufficient evidence to link him to the murder.
The prosecutor said the witchdoctor, Adangalwisye Kayuni, was found with human intestines whose DNA matched that of the dead teenager.
He added that another defendant was found in possession of four fingers and 10 bones, which DNA tests proved were also those of the victim.
The prosecutor said that the boy, Henry Mwakajila, went missing in the Mbeya region one night in 2008.
A Red Cross report said the court sentenced 15 people to death for killing albinos since 2008.
It said more than 75 people with albinism, a lack of pigment in the skin, hair and eyes, were killed in Tanzania since 2000.
The Red Cross added that the killers often hack their victims to death and sell their body parts to witchdoctors who used them in spells to bring good luck and wealth.
It said witchdoctors paid as much as 75,000 dollars for full albino body parts.
Albinism is a congenital disorder affecting about one in 20,000 people worldwide but more common in sub-Saharan Africa.
It affects an estimated one Tanzanian in 1,400.
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