GPA issue, and lost built house

My father in law purchased a site by GPA back in 1999 and constructed a house in 2000 in Bangalore. Prime locality now. When construction came to an end, he had purchased the site by owner by a GPA. There were 12 sites like this he had sold and my FIL was first to construct the house. When house was at the verge of completion, owner claimed back the site using rowdy power and my FIL lost the constructed house, all money and site along with 11 others. They tried hard to obtain it back from him with help of police, but owner was better at it, Police didnt do anything. After a year BDA acquired the site+house and someone else is there now. The compensation was given to old owner. Is there something can be done now? My father in law was worried for several years took a toll on him and passed away in 2006. My father in law has only daughter married to me. I would like to take people who cheated to justice. I am seeking guidance and support from this forum as what can be done please.