The Five people are: Daya, Mohan, Jaroon, Balu, and Ashok
By process of elimination, Jaroon’s leg is amuputated and is the murderer.
Dyaya couldn’t have run in Bangalore City Marathon, if his leg was amputated. Hence he is innocent.
Mohan was a farmer before he moved to the City. Since the murderer grew up together with his brother in Mysore, Mohan is not the brother of Ashok. Hence he is innocent.
Balu met Ashok for the first time six months ago. Hence he is not Ashok’s brother who grew up in Mysore. Balue is innocent.
Ashok is not the murderer, since his brother has committed the murder.
This leaves Jaroon, who is the murderer.