Second Grade Magistrate Thom Midiasi of Mkukula magistrate court in Dowa district handed down the sentence saying the teenager had compromised national security.
Midiasi said Mbalaka could have been given a suspended sentence considering his age and that he is first offender.
He observed that Mbalaka compromised national security by keeping the riot gun, saying that's why he decided to settle for a 13 month custodial sentence to send a warning to others who may have similar thoughts.
Central Region Police deputy public relations officer, Patrick Kasaula said the incident occurred on a day when demonstrations got out of hand which resulted in chaos.
“The demonstrators became violent and in the process people started attacking police officers. The accused and others stole some riot guns from the police armoured vehicle before setting the said vehicle ablaze,” he said.
Kasauka said investigations were instituted which led to the arrest of Mbalaka who was found in possession of the gun at his home at Chipasula in Lilongwe on August 8.
Mbalaka was charged with theft in line with Section 278 of the Penal Code.
Mbalaka hails from Magombo Village in Traditional Authority Chakhumbira in Ntcheu.