Tenant not vacating house

My Parents are elderly citizens (55+). We have two portions of our house which is rented. Our main income source is from rent. In 2014 Mar my father rented out the second floor for a rent of Rs 10,000/month and with a verbal agreement that the rent will be increased to Rs 12,000(which was initially quoted and reduced for the first six month since the tenant pleaded that he needs the house urgently and is facing a difficult time in terms of income). My father who is humble and helpful in nature agreed to it without any proper agreement. Now after Six months , In Sep 2014 when my father told the tenant that e had to pay Rs 12,000 as per verbal agreement, tenant denied and said in a rude manner that he wont pay Rs 12,000.Hence we have requested him to vacate the house giving him three months time (from Oct15 to Dec15). During the last week of December He has filled a case against my father stating that we have demanded Rs 20,000 rent and are threatening them by using external support(using rowdies). My mother is handicapped and my father has to care of my mother 24/7. I'm working hard to meet the medical expenses for my mother. Case is still going on in court. It has been more than a year. Please advise me how to proceed on this. How to vacate him from the house. Or can I ask him to pay the Rent amount of 12000 through any legal notice or Send him a eviction notice ? Please help me. Our family is totally distressed with this unruly and un heartening behaviour of the tenant.