The offence was committed in Nairobi’s Mathare area four months ago.
Magistrate Lucy Mbugua said the prosecution had proved beyond reasonable doubt that James Shisia Wanda committed the offence.
According to the prosecution, Wanda beat his son then cut his ear with a razorblade as his siblings and another relative watched.
“The offence committed by the accused was heinous, serious and grave,” the court ruled.
The court held that the offence was traumatising because apart from cutting his son’s ear, he tried forcing the boy to drink his blood.
During hearing, the court heard that the biological mother of the child has not been traced since the proceedings of the case began in July.
Wanda, a casual labourer in Westlands, returned home at 7.30pm on the fateful night drunk and asked the pre-unit pupil about an alleged theft from a neighbour.
But the boy denied the allegations levelled against him after which the father decided to mete out the inhuman punishment.
According to the prosecution, the accused was arrested after his sister in-law ran out to look for help and found police officers on patrol.
Police prosecutor Dancun Ondimu had urged the court to give the accused a maximum sentence to serve as a deterrent.
“If the attack by the accused continued it could have resulted in death. The court must therefore take into consideration the inhumane act and prevailing circumstances when the offence was committed,”
In mitigation, the accused urged the court to give him a non-custodial sentence, saying he is remorseful “for the shameful act.”